Boring factory 107" cylinders

[Adam76]

Thinking about doing a small increase in displacement on my 107" softail. I definitely don't want a "big bore kit" especially the 124 / 128" kits..... 114"/117" will be plenty power for me.

Is it safe to bore the 107" to 117" ? Or would it be a safer bet to just go to 114"?

I have found CP pistons and Wiseco both do the 117" pistons -- however, interestingly in the Wiseco catalogue, the 117" pistons require cylinder "Resleeve" ...

Any advice on which pitons to go with, and what size bore would be appreciated. Also need to make sure I can get a Cometic top end gasket kit to go with it.

Thanks.

[BigT]

I did a 117" build on my 2017 107" before they started making the 124" setups. I had good luck with the Wiesco pistons I got from Tman.
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[BigT]

I did a 117" build on my 2017 107" before they started making the 124" setups. I had good luck with the Wiesco pistons I got from Tman.
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I just remembered that I did start with the SE 114" cylinders which had a little thicker cylinder wall than the 107" cylinder. It was pretty common back then to take the 107" cylinders out to  4.125/117"

[Adam76]

Thanks BigT, do you reckon I should find some take off 114" cylinders just to be safe?

[BigT]

Thanks BigT, do you reckon I should find some take off 114" cylinders just to be safe?

I would personally, especially if you could find a set cheap.

[Ohio HD]

Depending on what you're looking for power wise. This is the cam that Rigidthumper spoke about that's only in OZ from Alpha Performance Engines right now.

These guys are in OZ.

Alpha Performance Engines

Their sheet is STD but still, lots of power from a 107"

[Adam76]

Wow, that's crazy power from a 107" 

[Ohio HD]

This is a CR483 that also is only available from Alpha Performance Engines. A broader power range. They don't say what size the motor was in the dyno run.

[JSD]

Adam also check Rams head services in Sydney. They do nice Heads for TC & M8 . Also the 124 kits are cheaper at moment as they have gone 128 or so and 131 on the 4 1/2"

[Adam76]

The 107" build by Alpha Performance you posted earlier  is an interesting build -- post #5.

If you simply add domed high comp pistons to a 107" motor that are the exact same bore as the stock pistons, what kind of machining is needed for the cylinders? Just a hone? How would they be an exact fit?

Thanks

[Ohio HD]

Probably buy some of the Cast Billet CP pistons in 0.005" Oversize. The cylinders need measured first to see where they are. Then just have a competent shop hone for the pistons.

Do not try to hone the cylinders +0.005" with home shop tools. They need to be honed by a precision honing system.

[JSD]

Ohio are you suggesting cast pistons? Interestingly i watched a tour of CP pistons factory. I see they dont use coating on the skirts as sold by S&S for example for a TC 3.937

[Adam76]

Probably buy some of the Cast Billet CP pistons in 0.005" Oversize. The cylinders need measured first to see where they are. Then just have a competent shop hone for the pistons.

Do not try to hone the cylinders +0.005" with home shop tools. They need to be honed by a precision honing system.

Thanks Ohio, if that's the case I might as well just buy the CP 4.08" pistons and bore my 107" cylinders to 114" with 11-1 compression. This will open up my cam selection a bit more and give me good streetable power.

[Adam76]

I did a 117" build on my 2017 107" before they started making the 124" setups. I had good luck with the Wiesco pistons I got from Tman.
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Hey bigT, did you have to resleeve your 107" cylinders like the wiseco catalogue suggests? Or did you just bore out the 107" to 117" with no issues?
Thanks

[Don D]

124" is cheap and reliable. Drag Specialties cylinders and KB595LCA005 pistons. If you are pulling apart, do not dabble. Make it run.

[NHBagger]

This is a CR483 that also is only available from Alpha Performance Engines. A broader power range. They don't say what size the motor was in the dyno run.

Top of the dyno sheet says it's a 114.
Also I believe Wes at CR does have a few of the CR483.
Rumor has it that cam will be in the new FM cam shootout.

[Ohio HD]

Top of the dyno sheet says it's a 114.
Also I believe Wes at CR does have a few of the CR483.
Rumor has it that cam will be in the new FM cam shootout.

Good eyes, I missed that.

I don't know the details on these two cams as far as who actually owns the specs / sales. If A.P.E. owns the specs and has an agreement with Cycle Rama, they may be the only dealer that has them. In any case I would think that A.P.E. would want to market them in the USA. As well it would benefit Cycle Rama.

[harpwrench]

Mastertechmiller on YouTube commented on one of his videos that the 485 has basically same timing as the 512, with lower lift.

[Adam76]

124" is cheap and reliable. Drag Specialties cylinders and KB595LCA005 pistons. If you are pulling apart, do not dabble. Make it run.

Yes, agreed. But the only thing stopping me from going straight to a 124" top end is the heavy duty clutch I'm going to need and with my busted left hand which gives me grief with anything heavier than the stock 107" clutch lever pull.
If there was a way to have a light clutch lever pull with a 124" motor, then I'm all in. 😁

[Adam76]

This is a CR483 that also is only available from Alpha Performance Engines. A broader power range. They don't say what size the motor was in the dyno run.

Top of the dyno sheet says it's a 114.
Also I believe Wes at CR does have a few of the CR483.
Rumor has it that cam will be in the new FM cam shootout.

I reckon a 114" big bore and a CR483 can would be ideal for what I want / need. 

[rigidthumper]

"I reckon a 114" big bore and a CR483 can would be ideal for what I want / need."
Add a Muller power clutch and Bob's your uncle!

[Adam76]

"I reckon a 114" big bore and a CR483 can would be ideal for what I want / need."
Add a Muller power clutch and Bob's your uncle!

Thanks, sounds like a plan.

Would a VP clutch be needed and what springs? STD or medium?

[Don D]

Don't forget there is a very good shop to do that work there
Hood Motor Service

[Adam76]

Don't forget there is a very good shop to do that work there
Hood Motor Service

Thanks Don, unfortunately he's in a different state, 3000 kms away so I'll have to find someone local.

What are your thoughts on a softail  slim exhaust for this build... Will S&S slip ons be good or do I need a good 2-1 pipe?

Cheers

[rigidthumper]

"I reckon a 114" big bore and a CR483 can would be ideal for what I want / need."
Add a Muller power clutch and Bob's your uncle!

Thanks, sounds like a plan.

Would a VP clutch be needed and what springs? STD or medium?

Use the heavy springs from HD (37000286)or EBC (CSK 236). That will hold all you need, and with the Muller setup, will make it pull like stock.

[Adam76]

"I reckon a 114" big bore and a CR483 can would be ideal for what I want / need."
Add a Muller power clutch and Bob's your uncle!

Great, now all I need to do is sort out an exhaust system....
Do you think a set of S&S slip ons will be good, or do I need a good 2-1 pipe?
Softails are always harder to get the exhaust right compared to baggers.
Thanks

[rigidthumper]

I saw some some testing on Facebook, and the Softails seemed to like the slip-ons for mild stage 2. RS468 had the best sound, but a TQ dip. Woods 22X, TTS100, Andrews 464, CR450 all work well low-mid, and will make 100HP (+/-) by factory redline with a proper tune. The 107 doesn't have enough compression for a lot of the mid/upper range cams

[Hossamania]

All decisions are economic.
Slip-ons will work, you might leave a bit of power on the table, but will you notice? Will spending the extra money (quite a bit) on a full system be worth the price for the little bit of extra power? If you lose races to your friends, then yes!! If you're just enjoying a nice scramble through the countryside, probably not.
You can always sell the slip-ons if they don't work for you, get the full system, and unfortunately pay for a new tune, but chasing horsepower is rarely cheap.

[NHBagger]

I saw some some testing on Facebook, and the Softails seemed to like the slip-ons for mild stage 2. RS468 had the best sound, but a TQ dip. Woods 22X, TTS100, Andrews 464, CR450 all work well low-mid, and will make 100HP (+/-) by factory redline with a proper tune. The 107 doesn't have enough compression for a lot of the mid/upper range cams

CR450???

[rigidthumper]

CR450 (I3/25, .450", E45/3, .430) was designed as a bolt in cam, pick up the right side better than the SE447. May not even be in production anymore.

[Adam76]

All decisions are economic.
Slip-ons will work, you might leave a bit of power on the table, but will you notice? Will spending the extra money (quite a bit) on a full system be worth the price for the little bit of extra power? If you lose races to your friends, then yes!! If you're just enjoying a nice scramble through the countryside, probably not.
You can always sell the slip-ons if they don't work for you, get the full system, and unfortunately pay for a new tune, but chasing horsepower is rarely cheap.

Thanks for the advice Hoss.

My racing days are over, I just like cruising the country side. But,  if I'm going to spend good money on a stage II then I also want to make sure the exhaust isn't going to rob me of too much power if you know what I mean.

[Adam76]

CR450 (I3/25, .450", E45/3, .430) was designed as a bolt in cam, pick up the right side better than the SE447. May not even be in production anymore.

I think you might mean the CR460 ? That was in production early on, not sure if it's available any more.

[rigidthumper]

Two different cams- specs and description from FM site
CR-450 specs were I 3/25, .450", E 45/3, .430" bolt in for M8 engines with stock or slightly higher compression.
CR-460 specs were I 6/20, .460", E 46/0, .440" bolt in for M8 engines with stock compression, broad power in 107,114, & 117 motors.

[Sunny Jim]

CR450 (I3/25, .450", E45/3, .430) was designed as a bolt in cam, pick up the right side better than the SE447. May not even be in production anymore.

I think you might mean the CR460 ? That was in production early on, not sure if it's available any more.

Great cam!!

[Adam76]

Doing the 107 - 114 big bore kit with JE pistons and the CR480 cam.

Do you guys recommend the larger injectors and 55mm throttle body? Or are they not needed for that level of mods?

Thanks

[JSD]

Talking to Geelong HD mate and recommends injectors and the Alloy manifold. 

[Adam76]

All decisions are economic.
Slip-ons will work, you might leave a bit of power on the table, but will you notice? Will spending the extra money (quite a bit) on a full system be worth the price for the little bit of extra power? If you lose races to your friends, then yes!! If you're just enjoying a nice scramble through the countryside, probably not.
You can always sell the slip-ons if they don't work for you, get the full system, and unfortunately pay for a new tune, but chasing horsepower is rarely cheap.

Agreed.

Taking about chasing HP... I feel like boring my 107" to 114" is almost not worth the cost for the small gain?

Some say it's fine to bore the 107 out to 117, others say it leaves the cylinder wall too thin...

The 120"/ 124" kit is probably more power that I need?

Starting with a 114" would have been much easier to work with. 

[rigidthumper]

"The 120"/ 124" kit is probably more power than I need?"
If it's truely Need? I'd think that a 107 with a cam/AC/slip-ons/tuner will provide that. 115-120 TQ, 100-107 HP, cam dependent. After that, it's gravy.

[Tail Ridr]

All decisions are economic.
Slip-ons will work, you might leave a bit of power on the table, but will you notice? Will spending the extra money (quite a bit) on a full system be worth the price for the little bit of extra power? If you lose races to your friends, then yes!! If you're just enjoying a nice scramble through the countryside, probably not.
You can always sell the slip-ons if they don't work for you, get the full system, and unfortunately pay for a new tune, but chasing horsepower is rarely cheap.

Agreed.

Taking about chasing HP... I feel like boring my 107" to 114" is almost not worth the cost for the small gain?

Some say it's fine to bore the 107 out to 117, others say it leaves the cylinder wall too thin...

The 120"/ 124" kit is probably more power that I need?

Starting with a 114" would have been much easier to work with. 

There are many routes to explore. In the end, to settle in your mind if it's worth it or really what is the best, after you figure what the final outcome is you're looking for...it all comes down to cost/hp-tq. In the 2 stroke world it was never uncommon to spend $100/hp. Is it ever really worth it? Seat of the pants and a smile gives you the answer.

[Adam76]

Thanks,

I'm replacing the plastic manifold with the 55mm S&S and the tappet cuffs.

Is it necessary to change the Cam sprocket to the oversize Andrews camshaft sprocket?

Thanks.

[HogMike]

Thinking about doing a small increase in displacement on my 107" softail. I definitely don't want a "big bore kit" especially the 124 / 128" kits..... 114"/117" will be plenty power for me.

Is it safe to bore the 107" to 117" ? Or would it be a safer bet to just go to 114"?

I have found CP pistons and Wiseco both do the 117" pistons -- however, interestingly in the Wiseco catalogue, the 117" pistons require cylinder "Resleeve" ...

Any advice on which pitons to go with, and what size bore would be appreciated. Also need to make sure I can get a Cometic top end gasket kit to go with it.

Thanks.

I would recommend being realistic with what your goals are and how you ride.
There are "tried and true packages" from various shops that will fill your needs.

In my case, with my 2019 bagger, I knew what the bike is going to be used for and what kind of torque curve i wanted. This is my long haul bike. HP a was not a concern and we did a mild, well-mannered build with great gas mileage and excellent passing power where you need it. 40K miles on this one with no issues.

My green bike is pretty much the opposite, more a solo bike with high HP at higher revs. Both have their place but both require different riding styles.

Talk to some of the shops who will do "real world builds" as opposed to dyno queens.

I was fortunate to get some solid advice from a shop that actually recommended another source for my last build! He knows how I ride! Thanks Steve. LOL

Good luck in your build.

[rigidthumper]

Thanks,

I'm replacing the plastic manifold with the 55mm S&S and the tappet cuffs.

Is it necessary to change the Cam sprocket to the Andrews camshaft sprocket?

Thanks.

Not necessary, but will tighten up the fit on the pinion shaft. What's a few more bux while you're spending a chunk?

[Adam76]

Thinking about doing a small increase in displacement on my 107" softail. I definitely don't want a "big bore kit" especially the 124 / 128" kits..... 114"/117" will be plenty power for me.

Is it safe to bore the 107" to 117" ? Or would it be a safer bet to just go to 114"?

I have found CP pistons and Wiseco both do the 117" pistons -- however, interestingly in the Wiseco catalogue, the 117" pistons require cylinder "Resleeve" ...

Any advice on which pitons to go with, and what size bore would be appreciated. Also need to make sure I can get a Cometic top end gasket kit to go with it.

Thanks.

I would recommend being realistic with what your goals are and how you ride.
There are "tried and true packages" from various shops that will fill your needs.

Good luck in your build.

Thanks Mike, yes realistically all I need is basic a 107" big bore build just boring my own cylinders to 117" with a set of 10.75 comp CP pistons.... . I'm already doing the full cam upgrade, so it's not that much more for the pistons and machine work... I definitely DO NOT need a 124" kit. More power (and money) than I could ever use or have.

I'll Beef up the clutch a little to hold the TQ and it's ready for a dyno tune. I have found a really good machine shop locally that is very reasonably priced, so I think I'm set. All I need to decide on is the camshaft itself..... Tossing up between the CR480 and the S&S475.

Thanks.

[JSD]

Adam the 475 cam on graphs shows a big dip in torque in some rev range 

[rigidthumper]

The 475 has more traditional lope sound @ idle, the 480 pulls better low/mid.

[Hossamania]

Would the 475 work better as a 117", making the low end dip much less of an issue?
Having asked that, it sure seems the 480 is a very well designed cam that hits all the marks, would only get better with more displacement. It would be my choice for any stock motor stage 2 upgrade.

[rigidthumper]

With a 17° close, the only worry is corrected compression. 9.6:1 corrected for Twin Cams did OK with a good tune, M8 seems to like 10.5 corrected. Everything can be pushed, but diminishing returns and all that.

[harpwrench]

This is a 475 in a 107 with a supertrapp fatshot 2-1. Maybe not useful since it's a touring and I don't know if they have one for softails, but I think it's interesting with a bonus torque hump instead of a dip.

You cannot see attachments on this board.

[Adam76]

This is a 475 in a 107 with a supertrapp fatshot 2-1. Maybe not useful since it's a touring and I don't know if they have one for softails, but I think it's interesting with a bonus torque hump instead of a dip

Thanks harpwrench,  that is indeed a very nice TQ curve and very nice HP numbers.

But I suspect you are right that the firing bike engine and exhaust configuration has a lot to do with it, and a softail even with a 2-1 pipe would not have the same results.

[Adam76]

With a 17° close, the only worry is corrected compression. 9.6:1 corrected for Twin Cams did OK with a good tune, M8 seems to like 10.5 corrected. Everything can be pushed, but diminishing returns and all that.

My cam chart says the CR480 has intake close of 20*.

Just got an email back from Jamie at Fuel moto saying the with the 107" that cam is more mid range 2700rpm - 5000rpm... And that the RS468 or Woods 2XE cam would have been a better choice for power from 2000rpm.

Looks like I have to change the cam, bump up the compression with the 114" big bore to get it working optimally.

[Ohio HD]

My sheets show the CR480 closes at 17°. Also the link below to Fuel Moto's site gives the same.

CR480 @ Fuel Moto

[Adam76]

My sheets show the CR480 closes at 17°. Also the link below to Fuel Moto's site gives the same.

CR480 @ Fuel Moto

Good catch, thanks 

[Adam76]

My sheets show the CR480 closes at 17°. Also the link below to Fuel Moto's site gives the same.

CR480 @ Fuel Moto

Looks like I'm stuck with the 107" displacement for a while. Funds aren't allowing the 114" big bore plans I had.

How does the CR480 cam hold up in a 107" softail??  Fuel Moto have advised me that it's more a mid range cam with most of the power from 2700rpm - 5000rpm. 

Maybe a good exhaust like the D&D Fat Cat might make it work better?  I'm looking for a nice broad TQ curve from 2000rpm - 4500 rpm. They suggested the Woods WM8-22X cam for good low - mid power in a 107 softail.

I haven't seen any love for the Woods 22X cam here on this forum... Is there a reason why?

Thanks

[Hossamania]

There is a tendency to chase horsepower, both on this forum and on barstools. The right cam choice needs to be made with clear goals in mind, the 22x seems to meet your needs.
Check the sticky threads in this section for testing multiple cams by Fuel Moto and Durwood.

https://harleytechtalk.com/htt/index.php/topic,102329.0.html

[Adam76]

There is a tendency to chase horsepower, both on this forum and on barstools. The right cam choice needs to be made with clear goals in mind.....

Not chasing HP at all.
Just trying to get the right combination of cam, displacement and exhaust to maximise the outcome and not be disappointed when it's done.
Thanks. 

It looks like exhaust choice also plays a big role in the 107" stage 2 builds.... Do you think the D&D Fat Cat is the best exhaust for the softail stage 2? Might be worth considering instead of the Bassani 2-1 I was going for.

Thanks

[Hossamania]

My comment about chasing horsepower was a general statement when builds and motors are discussed, that leads to sometimes choosing cams that aren't really what the owner wanted. All the cams tested by Fuel Moto in the link I included made over 100 lbs. of torque between 2000-3000 rpm, with the 22x seeming to make the most in that range, right where you're wanting it. It still made good horsepower at the top end, should you want to go there occasionally....

[Adam76]

My comment about chasing horsepower was a general statement when builds and motors are discussed, that leads to sometimes choosing cams that aren't really what the owner wanted....

Agreed. 
Thanks

[Adam76]

I'd think that a 107 with a cam/AC/slip-ons/tuner will provide that. 115-120 TQ, 100-107 HP, cam dependent. After that, it's gravy.

OK, totally fair point. BUT this is a Softail 107" not a tourer with the advantage of longer pipes and mufflers....  The more I look at the bolt in cams for the 107" more I see how exhaust sensitive they are...

What bolt in cam (RS468 / WM8-22X / CR480)  works with best with which exhaust / slip ons?  (S&S slash cut slip ons / D&D fat cat 2-1 / S&S super street 2-1 / Bassani RR 2-1 with Quiet baffle ?? or any others I've missed.

I feel like matching the exhaust and camshaft is really important when building a recipe for a good stage 2 softail 107"


EDIT:   ahh F*&k it, this is doing my head in.... I'm just going to get the CP 10.75 comp 4.125"  pistons and bore my 107" out to 117" with the CR480.  Proven winner.

[Hossamania]

Now you're talking!

[Deye76]

The S&S Superstreet 2 into 1 is longer than many other 2X1 pipes for M8 softails. Even with a CAT they perform very well IME.You cannot see attachments on this board.

[Adam76]

Now you're talking!

Is it still considered safe to bore 107 cylinders out to  117"  ??

[Adam76]

The S&S Superstreet 2 into 1 is longer than many other 2X1 pipes for M8 softails. Even with a CAT they perform very well IME.

Hey, thanks for the advice. Would I be losing any TQ if I took the Db reducer out of the S&S 2-1 super street pipe?
It's a little droning sounding with it in.
Cheers

[Adam76]

This is a CR483 that also is only available from Alpha Performance Engines. A broader power range. They don't say what size the motor was in the dyno run.

Thanks Ohio. I've decided to keep my CR480 cam and just build on that.

I'm trying to match a set of 107" - 114"  big bore pistons to a set of Cometic Head Gaskets...   (I don't want to bore my factory cy;linders to 117" just to be on the safe side).

JE pistons list their 107"  - 114" pistons as having a bore size of  4.080"

But I can't find Cometic Head Gaskets in that bore size -- I can only see the 4.075" bore size gaskets which is smaller than the actual piston size??

This is confusing. I've also read on Fuel Moto's site that they no longer bore factory cylinders.... which makes me definitely wary of going to 117" (4.125")  on my factory cylinders.
Thanks in advance for any explanation of what size / application I need.
Cheers

[FLSTFIDave]

The S&S Superstreet 2 into 1 is longer than many other 2X1 pipes for M8 softails. Even with a CAT they perform very well IME.You cannot see attachments on this board.

Nice build.  A whole lot of why the CR-480 is liked by so many.

[Deye76]

The S&S Superstreet 2 into 1 is longer than many other 2X1 pipes for M8 softails. Even with a CAT they perform very well IME.

Hey, thanks for the advice. Would I be losing any TQ if I took the Db reducer out of the S&S 2-1 super street pipe?
It's a little droning sounding with it in.
Cheers

I'd leave it as is. I like that it's fairly quiet at steady cruise, and emits a decent bark under full throttle.

[Adam76]

Anyone know if Cometic make head gaskets with 4.08" bore size?

Id like to use JE 107" - 114" big bore pistons which are listed as having a bore size of  4.080"

But the only Cometic head gasket size I can find is 4.075" which is smaller than the actual bore size?

[Ohio HD]

Any of the motor machine shops and builders listed in the vendor section of HTT can be a one stop shopping for pistons and gaskets.

[JSD]

Adam S&S have bigger kits now so you can pic up a 124 a lot cheaper. Check there site. I see some shops in OZ doing good prices on the S$S 124 kits. I think they are 11.1 so is the 480 suitable i ask ?

[Adam76]

I couldn't find the right size head gasket (4.080") to go with a set of JE 4.080"  107"-114" pistons.....  Could only find Cometic 4.075"  size HGs.

So unless it is no longer recommended ??  I'll have to bore my stock 107 cylinders to fit a set of 4.125"  CP 10.75 comp pistons to bring me to 117"....
This is the most economical big bore build for me and all the power I will ever need.

Thanks.

[rigidthumper]

I'd get a set of 114/117 take off cylinders if you are going to 4.125.

[boooby1744]

I couldn't find the right size head gasket (4.080") to go with a set of JE 4.080"  107"-114" pistons.....  Could only find Cometic 4.075"  size HGs.

So unless it is no longer recommended ??  I'll have to bore my stock 107 cylinders to fit a set of 4.125"  CP 10.75 comp pistons to bring me to 117"....
This is the most economical big bore build for me and all the power I will ever need.

Thanks.

Cometic can probably make any gasket you need.

[kd]

I couldn't find the right size head gasket (4.080") to go with a set of JE 4.080"  107"-114" pistons.....  Could only find Cometic 4.075"  size HGs.

So unless it is no longer recommended ??  I'll have to bore my stock 107 cylinders to fit a set of 4.125"  CP 10.75 comp pistons to bring me to 117"....
This is the most economical big bore build for me and all the power I will ever need.

Thanks.

Cometic can probably make any gasket you need.

    I would call them if you can't find them in their catalogue.  I would be surprised they don't have them.  In the past they have made the claim that if they have the correct material dimensions they will make it for you and there is normally no extra surcharge.  Don't forget to ask though.  If they are making them for you, get an extra set.

[Adam76]

I'd get a set of 114/117 take off cylinders if you are going to 4.125.

OK thanks, I was told that the 114" and 117" cylinders don't work on a 107" engine due to the different stroke....
How would you get them to fit a 107" without the pistons sitting waaay down the hole?

Thanks

[Ohio HD]

Cylinder heights are all the same. Pistons change with the stroke change. The compression height of the piston changes. 

[Adam76]

Cylinder heights are all the same. Pistons change with the stroke change. The compression height of the piston changes. 

OK thanks, that makes sense.

So what / which pistons do I need to use the 114" cylinders on a 107" stroke button end?

[Ohio HD]

You need 1.143" compression height x what ever bore you're looking for.

[harpwrench]

Screamin eagle piston kit for converting 107 to 114 is part number 21900084, 11:1 compression, I'm guessing they sell head gaskets as well

Edit sorry now I see you're asking about 117 pistons

[Ohio HD]

And if you bore to 4.125" you can use CP BHM8117-FT pistons.

[Adam76]

And if you bore to 4.125" you can use CP BHM8117-FT pistons.

Thanks Ohio, I just need to know if it's still considered safe to bore out stock 107 cylinders to 4.125" ??
Or are youtalking about factory 114" cylinders?

Thanks  sorry for the confusion.

[Ohio HD]

See reply number 69.

https://harleytechtalk.com/htt/index.php/topic,119199.msg1429456.html#msg1429456

[Adam76]

See reply number 69.

https://harleytechtalk.com/htt/index.php/topic,119199.msg1429456.html#msg1429456

Great, Thanks.

So 114" / 117" cylinders
BHM8117-FT pistons.
On a 107"  4.375" stroke bottom end.

So have I got that right now? 
Cheers

[Adam76]

Screamin eagle piston kit for converting 107 to 114 is part number 21900084, 11:1 compression, I'm guessing they sell head gaskets as well

Edit sorry now I see you're asking about 117 pistons

Thanks harpwrench,

114" / 117" it doesn't really matter as long as I can match the correct pistons, with the correct cylinders and the correct size MLS Cometic head gaskets for the bore size. Which seems to be very confusing.

[rigidthumper]

Have them bored for your CP 4.125 pistons, to make your 107 a 117.

[Ohio HD]

[Adam76]

And if you bore to 4.125" you can use CP BHM8117-FT pistons.

Thanks Ohio. Yes I understand that the pistons listed above are the correct ones used to bore my factory 107" cylinders out to 117"

But both you and a few others, including Rigidthumper have advised me to use "take off" 114" or 117" Cylinders instead...

So if I use a set of factory "114" cylinders on my 4.375" stroke motor, what exact 4.125" bore pistons do I need??

Apologies for the repeated question, but your posts #77 and #79 contradict each other. 

Not trying to be a pain in the ass, I really appreciate your efforts in trying to help me out here. 

[Adam76]

I'd get a set of 114/117 take off cylinders if you are going to 4.125.

No problem, sounds good.

But which 4.125" pistons exactly are are going to work with the 114" factory cylinders you've suggested I put onto my 107" bottom end?

Man this is ridiculously confusing. Sorry.   

[Ohio HD]

And if you bore to 4.125" you can use CP BHM8117-FT pistons.

Thanks Ohio. Yes I understand that the pistons above are the correct ones used to bore my factory 107" cylinders out to 117" and I'm happy to do that if there's enough thickness in the cyl wall.... But both you and a few others, including Rigidthumper have advised me to use "take off" 114" or 117" Cylinders instead...

So if I use a set of factory "114" cylinders on my 4.375" stroke motor, what exact 4.125" bore pistons do I need??

Apologies for the repeated question, but your posts #77 and #79 contradict each other. 

Not trying to be a pain in the ass, I really appreciate your efforts in trying to help me out here. 

They do not contradict each other.

Post #77 I said to use the pistons I've mentioned a few times.
Post #79 I said to see the post #69 by Ridgedthumper saying use 114 / 117 OEM takeoffs.

How does that contradict? 

The CP piston number that answers your question I've posted the answer twice already.

Then you must bore the cylinders to 4.125". It's simple!   

[Adam76]

And if you bore to 4.125" you can use CP BHM8117-FT pistons.

Thanks Ohio. Yes I understand that the pistons above are the correct ones used to bore my factory 107" cylinders out to 117" and I'm happy to do that if there's enough thickness in the cyl wall.... But both you and a few others, including Rigidthumper have advised me to use "take off" 114" or 117" Cylinders instead...

So if I use a set of factory "114" cylinders on my 4.375" stroke motor, what exact 4.125" bore pistons do I need??

Apologies for the repeated question, but your posts #77 and #79 contradict each other. 

Not trying to be a pain in the ass, I really appreciate your efforts in trying to help me out here. 

They do not contradict each other.

Post #77 I said to use the pistons I've mentioned a few times.
Post #79 I said to see the post #69 by Ridgedthumper saying use 114 / 117 OEM takeoffs.

How does that contradict? 

The CP piston number that answers your question I've posted the answer twice already.

Then you must bore the cylinders to 4.125". It's simple!   

Sorry, my question should have been -- if I used a set of  114" cylinders like Rigidthumper has suggested, what pistons are compatible with the cylinders that are now .070" taller on my 4.375" stroke motor  ?

Thats' all I was trying to work out.

Thanks

[Ohio HD]

harpwrench already answered in post #76. To use 114 cylinders (bored 4.075", standard 114" cylinders you use what he said to use SE 21900084 pistons.

I said, now the third time, use CP BHM8117-FT for these same cylinders and bored to 4.125".

[Adam76]

harpwrench already answered in post #76. To use 114 cylinders (bored 4.075", standard 114" cylinders you use what he said to use SE 21900084 pistons.

I said, now the third time, use CP BHM8117-FT for these same cylinders and bored to 4.125".

Ok, I thank you Sir, for the third time. 

Use 114" cylinders with the CP BHM8117-FT pistons to get me to 117"



Pheeew. That was painful.

[rigidthumper]

The 107 and the 114/117 cylinders are the same height. 107 cylinders have had issues taking them to 4 1/8". The 114/117 cylinders have more meat in the liner, making them the better choice to bore to 4.125. Actually, they can go to 4.180 to make a 120" if you wish.
LINK

[Ohio HD]

The best example that I could find to show stoke change, and compression height change in a piston is this link to a performance Ford motor site. The basics stay the same if you're thinking car or motorcycle.

We'll use figure 1 as a 107" motor and figure 2 as a 114" motor.

Compression height is the distance of the piston pin to the top of the piston flat, not including any dome.

When the stroke increases as in a 114" motor, something has to change to allow the piston to stay within the cylinder and not extend outside the bore. What changes is the compression height of the piston, the pin center to piston top.

What piston manufacturers do to mix a shorter stroke to a larger bore as when 114" cylinders are used on a 107" motor. They make a custom piston in the bore required (could be a stock 114" motor bore, or in a desired 4.125" bore or other bore size) with a compression height (pin location in the piston) to match the stroke being used.

All of this is based on using cylinders that are the same height. And we know the 107", 114" and 117" motors use the same OEM height cylinder from the factory. There are other things that effect compression height, rod length, cylinder length and we covered stroke. But in the case of M8 107", 114" and 117" motors, the rod length and cylinder length all stay the same.





Example of motor before and after a stroke increase.

[kd]

      As usual, you nailed it.  That should be easy enough for Adam or anyone else considering this engine modification to understand.

[Ohio HD]

All of the motor component swaps can be confusing. And just because I've been around it for a lot of years doesn't mean it's something everyone knows the details surrounding the changes. I could have been more explanative in my posts.

[Tail Ridr]

The 107 and the 114/117 cylinders are the same height. 107 cylinders have had issues taking them to 4 1/8". The 114/117 cylinders have more meat in the liner, making them the better choice to bore to 4.125. Actually, they can go to 4.180 to make a 120" if you wish.
LINK

If I were to buy a set of cylinders to bore, I would surely go to the 120, like Suburban's kit, and likely a different cam. (But that's another story)

[Adam76]

The 107 and the 114/117 cylinders are the same height.

Thanks, this was the detail that was tripping me up.
Thanks again for clarifying. 

[Adam76]

All of the motor component swaps can be confusing. And just because I've been around it for a lot of years doesn't mean it's something everyone knows the details surrounding the changes. I could have been more explanative in my posts.

Hey no worries, thanks for your help and patience.... I can be a bit of a slow learner at times but I totally get it now. 

[Adam76]

The 107 and the 114/117 cylinders are the same height. 107 cylinders have had issues taking them to 4 1/8". The 114/117 cylinders have more meat in the liner, making them the better choice to bore to 4.125. Actually, they can go to 4.180 to make a 120" if you wish.
LINK

If I were to buy a set of cylinders to bore, I would surely go to the 120, like Suburban's kit, and likely a different cam. (But that's another story)

Thanks guys,  I'm probably going to stay at 117" because I only have 5.5 injectors..... Not sure what size injectors the 120" would need.

I just picked up a set of 114" take off cylinders from a 2021 low rider,  so I'm half way there 

Now I just have to order the pistons and pick a camshaft.....

[Adam76]

I have sourced a set of take off 114" cylinders and have just ordered the CP BHM8117-FT pistons. And the Star 30-30 camshaft.

I have a competent machinist lined up to bore and hone with torque plates and I should be good to go.

How far are the pistons usually down the hole on these M8 motors?
Looking at a set of  Cometic Head and base gaskets of .010" base and .030" head gaskets. But will probably wait until mock up just to be sure.

[kd]

I have sourced a set of take off 114" cylinders and have just ordered the CP BHM8117-FT pistons. And the Star 30-30 camshaft.

I have a competent machinist lined up to bore and hone with torque plates and I should be good to go.

How far are the pistons usually down the hole on these M8 motors?
Looking at a set of  Cometic Head and base gaskets of .010" base and .030" head gaskets. But will probably wait until mock up just to be sure.

.

By all means wait and mock it up.  Gaskets can be ordered and received quick by mail so no worries.  There's even a possibility you could need to face the barrels to get things in reach for your gasket choices. Taking care of the details usually pays dividends.

[Adam76]

I have sourced a set of take off 114" cylinders and have just ordered the CP BHM8117-FT pistons. And the Star 30-30 camshaft.

I have a competent machinist lined up to bore and hone with torque plates and I should be good to go.

How far are the pistons usually down the hole on these M8 motors?
Looking at a set of  Cometic Head and base gaskets of .010" base and .030" head gaskets. But will probably wait until mock up just to be sure.

.

By all means wait and mock it up.  Gaskets can be ordered and received quick by mail so no worries.  There's even a possibility you could need to face the barrels to get things in reach for your gasket choices. Taking care of the details usually pays dividends.

Thanks, I thought so.

I was just curious to see what the "standard" was for the M8 motors as far as how far down the hole the pistons usually are.

I'm hoping to get to s close to zero deck height as possible just by using a thinner cylinder BASE gasket rather than having to face the barrels...

Cheers

[rigidthumper]

The pistons you've chosen will put the deck height ~.004" down with standard length M8 cylinders and a .010" base gasket. 10.7:1 CR with a .040" HG, 10.9:1 with a .030" HG.
Star 30-30 designed for stock compression, 10.17:1 corrected.
Star 30-30 with a .040" head gasket would be 10.35:1 corrected.
Star 30-30 with a .030" head gasket would be 10.56:1 corrected.

[Adam76]

The pistons you've chosen will put the deck height ~.004" down with standard length M8 cylinders and a .010" base gasket. 10.7:1 CR with a .040" HG, 10.9:1 with a .030" HG.
Star 30-30 designed for stock compression, 10.17:1 corrected.
Star 30-30 with a .040" head gasket would be 10.35:1 corrected.
Star 30-30 with a .030" head gasket would be 10.56:1 corrected.

Thanks, so with your calculations above it I get it right, I should use

.014" cyl base gaskets to give me zero deck height.

And .030" head gasket to give me .030" squish?

Thanks

[FXDBI]

The pistons you've chosen will put the deck height ~.004" down with standard length M8 cylinders and a .010" base gasket. 10.7:1 CR with a .040" HG, 10.9:1 with a .030" HG.
Star 30-30 designed for stock compression, 10.17:1 corrected.
Star 30-30 with a .040" head gasket would be 10.35:1 corrected.
Star 30-30 with a .030" head gasket would be 10.56:1 corrected.

Thanks, so with your calculations above it I get it right, I should use

.014" cyl base gaskets to give me zero deck height.

And .030" head gasket to give me .030" squish?

Thanks

.006 base gasket to get 0 a .014 will give you .008.   Bob

[Adam76]

The pistons you've chosen will put the deck height ~.004" down with standard length M8 cylinders and a .010" base gasket. 10.7:1 CR with a .040" HG, 10.9:1 with a .030" HG.
Star 30-30 designed for stock compression, 10.17:1 corrected.
Star 30-30 with a .040" head gasket would be 10.35:1 corrected.
Star 30-30 with a .030" head gasket would be 10.56:1 corrected.

Thanks, so with your calculations above it I get it right, I should use

.014" cyl base gaskets to give me zero deck height.

And .030" head gasket to give me .030" squish?

Thanks

.006 base gasket to get 0 a .014 will give you .008.   Bob

Thanks Bob. I'm not sure Cometic make a .006" base gasket? Lowest I can find is .010"

[kd]

The pistons you've chosen will put the deck height ~.004" down with standard length M8 cylinders and a .010" base gasket. 10.7:1 CR with a .040" HG, 10.9:1 with a .030" HG.
Star 30-30 designed for stock compression, 10.17:1 corrected.
Star 30-30 with a .040" head gasket would be 10.35:1 corrected.
Star 30-30 with a .030" head gasket would be 10.56:1 corrected.

Thanks, so with your calculations above it I get it right, I should use

.014" cyl base gaskets to give me zero deck height.

And .030" head gasket to give me .030" squish?

Thanks

.006 base gasket to get 0 a .014 will give you .008.   Bob

Thanks Bob. I'm not sure Cometic make a .006" base gasket? Lowest I can find is .010"

I do believe they make MLS head gaskets in .027.  That will give you .031 quench (squish).  I'd say that's barely negligible and good enough for the girls I go out with.     Wait until you mock up before you order any base and head gaskets. 

BTW, cleaning up the barrel gasket surfaces isn't a bad thing.  We're talking .004" here.  Pull out your feeler gauges and you will see .004 is just enough to ensure the gasket surfaces are smooth and true.

[Adam76]

The pistons you've chosen will put the deck height ~.004" down with standard length M8 cylinders and a .010" base gasket. 10.7:1 CR with a .040" HG, 10.9:1 with a .030" HG.
Star 30-30 designed for stock compression, 10.17:1 corrected.
Star 30-30 with a .040" head gasket would be 10.35:1 corrected.
Star 30-30 with a .030" head gasket would be 10.56:1 corrected.

Thanks, so with your calculations above it I get it right, I should use

.014" cyl base gaskets to give me zero deck height.

And .030" head gasket to give me .030" squish?

Thanks

.006 base gasket to get 0 a .014 will give you .008.   Bob

Thanks Bob. I'm not sure Cometic make a .006" base gasket? Lowest I can find is .010"

I do believe they make MLS head gaskets in .027.  That will give you .031 quench (squish).  I'd say that's barely negligible and good enough for the girls I go out with.     Wait until you mock up before you order any base and head gaskets. 

BTW, cleaning up the barrel gasket surfaces isn't a bad thing.  We're talking .004" here.  Pull out your feeler gauges and you will see .004 is just enough to ensure the gasket surfaces are smooth and true.

Thanks kd, so you recommend taking a few thou of the base of the barrels as well as the tops of the barrels to ensure nice flat smooth surface?

Of course depending on how far down the hole the pistons are 

[kd]

The pistons you've chosen will put the deck height ~.004" down with standard length M8 cylinders and a .010" base gasket. 10.7:1 CR with a .040" HG, 10.9:1 with a .030" HG.
Star 30-30 designed for stock compression, 10.17:1 corrected.
Star 30-30 with a .040" head gasket would be 10.35:1 corrected.
Star 30-30 with a .030" head gasket would be 10.56:1 corrected.

Thanks, so with your calculations above it I get it right, I should use

.014" cyl base gaskets to give me zero deck height.

And .030" head gasket to give me .030" squish?

Thanks

.006 base gasket to get 0 a .014 will give you .008.   Bob

Thanks Bob. I'm not sure Cometic make a .006" base gasket? Lowest I can find is .010"

I do believe they make MLS head gaskets in .027.  That will give you .031 quench (squish).  I'd say that's barely negligible and good enough for the girls I go out with.     Wait until you mock up before you order any base and head gaskets. 

BTW, cleaning up the barrel gasket surfaces isn't a bad thing.  We're talking .004" here.  Pull out your feeler gauges and you will see .004 is just enough to ensure the gasket surfaces are smooth and true.

Thanks kd, so you recommend taking a few thou of the base of the barrels as well as the tops of the barrels to ensure nice flat smooth surface?

Of course depending on how far down the hole the pistons are 

Because it's only .004 doing the top and bottom will be a very fine .002 each.  You can opt for top "or" the bottom for the full .004".  With so little coming off, if you chose the bottom it shouldn't effect the intake manifold fit. Taking it off the top doesn't change anything but the piston deck height and it's probably cheaper doing one or the other as it's only one operation per cylinder. It's a decent option for an OCD build that may allow you to access common gaskets.  Believe me, I know how that OCD stuff works.    You'll get your zero deck and hopefully can manage the .030 head gasket you desire. 

Now that you are familiar with the Big Boyz calculators you will have to determine the head cc you need to satisfy the correct compression for the cam you chose or choose. You may be good where you are at with zero deck.  It's part of the planning process and journey that  never seems to end, but it will, with a well put together combination. 

[Ohio HD]

Adam, I agree with what rigidthumper said, my math and not measuring the piston should be 0.004" in the cylinder. I'm of the mind that the 0.004" won't kill anything. But I would ask Cometic as KD suggested for an MLS head gasket 0.026" thick. That would get you to zero deck if everything measures as we think it will. Even if you leave it at 0.004", and use an 0.030" head gasket, it's not going to mean all that much performance wise. At least not through the midrange. I let my 124" Twin Cam go at 0.035" squish. For a street motor, that's still much better than OEM. 

I've read a lot of good about the 30-30 cams, just haven't seen the results. But George Bryce puts out some quality parts. I'd give them a try. 


Below is how I come up with the piston depth data. We just use the known design and some OEM measured part dimensions of the parts. But all parts have a tolerance, so it could be a little more or less. That's why measuring should be a must.


You cannot see attachments on this board.

[Adam76]

Thanks kd and Ohio, really appreciate the details and information you posted.

Super helpful. 

[Adam76]

The pistons you've chosen will put the deck height ~.004" down with standard length M8 cylinders and a .010" base gasket. 10.7:1 CR with a .040" HG, 10.9:1 with a .030" HG.
Star 30-30 designed for stock compression, 10.17:1 corrected.
Star 30-30 with a .040" head gasket would be 10.35:1 corrected.
Star 30-30 with a .030" head gasket would be 10.56:1 corrected.

This has me worried, as I was hoping to get close to zero deck height and use a .030" head gasket for good squish.... But now that looks like it's too much compression?

My calculator has me at 11.15 static and with the 30-30 cam's intake close of 25* corrected comp is 10.8  /  233 ccp. I'm thinking that might be much too high...

I've reached out to George Bryce to get his opinion on the compression limits of the 30-30 cam in a 117".

[Adam76]

The pistons you've chosen will put the deck height ~.004" down with standard length M8 cylinders and a .010" base gasket. 10.7:1 CR with a .040" HG, 10.9:1 with a .030" HG.
Star 30-30 designed for stock compression, 10.17:1 corrected.
Star 30-30 with a .040" head gasket would be 10.35:1 corrected.
Star 30-30 with a .030" head gasket would be 10.56:1 corrected.

This has me worried, as I was hoping to get close to zero deck height and use a .030" head gasket for good squish.... But now that looks like it's too much compression?

My calculator -- with the pistons .007" down -- has me at 11 static and with the 30-30 cam's intake close of 25* corrected comp is 10.68  /  230 ccp. I'm thinking that might be much too high...

I've reached out to George Bryce to get his opinion on the compression limits of the 30-30 cam in a 117".

[Ohio HD]

I get pretty close to what Rigidthumper gets.

[Deye76]

Bryce says anywhere between 10 & 11 corrected is "perfect".

[kd]

Bryce says anywhere between 10 & 11 corrected is "perfect".

If that's the answer Adam gets back from George, he'll be in the game.  Being near the upper level will bring in the torque earlier (which I believe is the stated goal) and will require attention to a good tune.  With the extra compression, the .030 quench will up the combustion turbulence and help defend against it becoming a ping machine.

[Adam76]

Bryce says anywhere between 10 & 11 corrected is "perfect".

If that's the answer Adam gets back from George, he'll be in the game.  Being near the upper level will bring in the torque earlier (which I believe is the stated goal) and will require attention to a good tune.  With the extra compression, the .030 quench will up the combustion turbulence and help defend against it becoming a ping machine.

Yes, thanks guys. 
Bryce says 11:1 comp is fine.
He advised on using a .040" head gasket to allow for greater piston to head clearance and trapping more air in to the chamber etc.

Plan is
1. Measure deck height
2. Mill bottom of pistons approx .005" to get closer to zero deck height
3. Use a .010" base gasket
4. CC heads just to make sure they are not too far off the STD 86.5cc
5. Use a .040" head gasket
6. Full custom tune on the dyno

[kd]

Well it sounds like it's coming together nicely. You won't be sorry that you took care of the details before diving in.

[JSD]

Adam you say mill bottom of pistons? Do you mean cylinders? 

[Adam76]

Adam you say mill bottom of pistons? Do you mean cylinders?

Yes, sorry.... typo. 

[Adam76]

Interestingly,  I got this info from George Bryce himself regarding the use of the Star 30-30 cam in my build...

I use .040 piston to head clearance   
Close but not too close. The would idea is to let more air in (30-30) cam to trap more mixture (25) closing to add cylinder pressure to make more power.

Looks like if I can get zero deck height, I'll go with a .040" HG.  Interesting,  as I always thought .030"- .035" was the idea lsquish.  Learn something new every day

[JSD]

I would not go above .038". But Star knows 

[VernDiesel]

Adam looking forward to your results. I have a softail stage 3 107 to 114. 11-1 SE-498 cam S&S Super Street 2-1 with Cat & SE Pro tuner.  It made 116/116.  Since then I added Fueling oil tank breather & a larger Db reducer. Then won a free dyno pull. It pulled 118/122. It picked up some sound volume but is not loud.  Bike still seems to be on point in every way. Part of me hates to mess with it. Been happy with it for over 3 years and 37k but now am trying to get more. 

Had wanted a 139ci but all considered have decided against it. Am & have considered a 128ci build. Really nice CP pistons, jugs, still its some coin.  But am also considered what I could do with existing jugs and Star's new F35A cam. Thinking having Wards port my intake. I'd gut the cat and swap to PV tuner.

George say's the F35A is designed to fit in a stock engine. It closes 10 degrees later than the 30 30 at 35 after bottom, has 572 lift, and is designed for 10.5 to 11.5-1.

We will perform leak down test & check crank runout. Just a hot rodder and ever learning hobbyist here. So this thread sparked me. If we decide to pull the heads and jugs to re ring freshen cylinders and make sure everything is square and seals good. Well then ridgidthumper goes and posts you could go 4.180 make it a 120ci and posts a link. $375 a piston isn't much. It would already come with fresh rings. Not much more to bore it. Only it says 12.0-1. 11.5-1 sounds safer and meets George's listing. Not sure I fully follow all these measurements and know all my options here. I'd be the assistant anyway but would be interested in what you all might suggest.

"He (Bryce) advised on using a .040" head gasket to allow for greater piston to head clearance and trapping more air in to the chamber etc."  I thought that was interesting.  George thinks deep.

[Adam76]

Adam looking forward to your results. I have a softail stage 3 107 to 114. 11-1 SE-498 cam S&S Super Street 2-1 with Cat & SE Pro tuner.  It made 116/116.  Since then I added Fueling oil tank breather & a larger Db reducer. Then won a free dyno pull. It pulled 118/122. It picked up some sound volume but is not loud.  Bike still seems to be on point in every way. Part of me hates to mess with it. Been happy with it for over 3 years and 37k but now am trying to get more. 

Had wanted a 139ci but all considered have decided against it. Am & have considered a 128ci build. Really nice CP pistons, jugs, still its some coin.  But am also considered what I could do with existing jugs and Star's new F35A cam. Thinking having Wards port my intake. I'd gut the cat and swap to PV tuner.

George say's the F35A is designed to fit in a stock engine. It closes 10 degrees later than the 30 30 at 35 after bottom, has 572 lift, and is designed for 10.5 to 11.5-1.

We will perform leak down test & check crank runout. Just a hot rodder and ever learning hobbyist here. So this thread sparked me. If we decide to pull the heads and jugs to re ring freshen cylinders and make sure everything is square and seals good. Well then ridgidthumper goes and posts you could go 4.180 make it a 120ci and posts a link. $375 a piston isn't much. It would already come with fresh rings. Not much more to bore it. Only it says 12.0-1. 11.5-1 sounds safer and meets George's listing. Not sure I fully follow all these measurements and know all my options here. I'd be the assistant anyway but would be interested in what you all might suggest.

"He (Bryce) advised on using a .040" head gasket to allow for greater piston to head clearance and trapping more air in to the chamber etc."  I thought that was interesting.  George thinks deep.

Yes, theres definitely plenty of options out there for big bore M8 builds...

The comment Bryce made about the .040" HG in my application of the Star 30-30 was assuming I have a zero deck height. If I had .004" below deck height, the ideal HG thickness might be something different...  0.036" maybe, which Cometic actually make.

[Adam76]

I would not go above .038". But Star knows

Thanks, yes I thought Bryce would know better than anyone.

Now that my build is sorted, what 2-1 exhaust is best for the M8 softails??

* S&S super street seems very popular.
* Supertrapp Fatshot?
* Bassani Road Rage II / III with quiet baffle?

I've seen a lot about how exhaust sensitive these builds can be and don't want to get this far and stuff it up with a poor exhaust choice. 

[Adam76]

Well it sounds like it's coming together nicely. You won't be sorry that you took care of the details before diving in.

Thanks kd,

The last part of the puzzle is the exhaust....

The M8 softails are very exhaust sensitive, and I don't want to mess up my build with a poor exhaust choice.

What would you say are the best 2-1 exhaust systems for my application?

Thanks

[VernDiesel]

Adam been real pleased with my S&S Super street. The Fuel Moto Db reducer is a great tip if you start making power and want to improve its sound without having something too loud. It already freed up some flow & power from 116/116 to 118/122.

Are the two calculators you guys listed on line somewhere.  Going to try to figure out my options for a 120 build.

[Adam76]

Adam been real pleased with my S&S Super street. The Fuel Moto Db reducer is a great tip if you start making power and want to improve its sound without having something too loud. It already freed up some flow & power from 116/116 to 118/122.

Thanks Vern, can you tell me a bit more about the Fuel Moto insert you are talking about? How is it different to the S&S Db reducer that comes with the exhaust?

Thanks

[VernDiesel]

S&S Super street Db reducer is 1 3/4" diameter. Fuel Moto is 1 7/8 diameter. I used the longer non louvered. I just cut it to the same length internally as to the stock Db reducer. This cut off the tuning tongue. The shorter inserts would allow for the use of the tuning tongue but as you have seen from my dyno chart in the dyno section I didn't have dip to contend with. Later I also used some even larger pipe but you are safe with the Fuel Moto.

https://www.fuelmotousa.com/i-23898837-fuel-moto-dynamic-exhaust-tuning-inserts.html#!make%3DHARLEY-DAVIDSON

Sorry not sure how to make that link work.  Its FM home. Then drop down exhaust menu, pick exhaust accessories, then click item 17 exhaust tuning inserts.

[VernDiesel]

rigidthumper, Earlier in this thread you linked a Suburban HD page with 4.180 piston & cylinder kits that could go with the cylinders & 4.375 stroke that Adam has. I already have I believe the same or same length cylinders from my now 3 1/2 year old 37k mile MoCo stage 3 107 to 114 kit. And the factory 2019 107 I believe 88cc heads. I see Suburban has just the piston kit; SS148185D08. The site says these pistons have an 8cc dome to get compression up to 12.0-1 with 88cc heads.

Earlier I said I was considering Star's new F35A cam. George say's its designed to fit in a stock engine. It closes 10 degrees later than the 30 30 at 35 after bottom, has 572 lift and is designed for 10.5 to 11.5-1. I have 64mm TB & intake and am thinking of having Wards port the intake. Suburban also lists exchange heads so I should probably do that as well as I am not trying to leave much on the table. Would you have any concerns with this combo?

Naturally in construction terms measure twice cut once. I am a hobbyist here not a pro builder. But would you have concern that the compression or cranking compression be too high that it risks detonation? Or that measurements would be too close that it risks valve piston contact? Any ideas suggestions or options I should consider? All suggestions concerns welcome.


Ohio HD,  You must be somewhat local to me.  I see your link but are you also affiliated to a local speed/machine shop?

[rigidthumper]

What are your goals? I've seen 150TQ & 125HP with stock heads and a 124 kit. At this power level, I would get the 124" cylinder/piston combo. Not that much more money, but an easy displacement bump. Pistons available from 11:1 and up. Ward ported heads/TB, 11.5:1CR, Georges cam, 64TB, 145+TQ 130+HP should be in the neighborhood (after proper tuning).

[Adam76]

What are you guys recommending for softail exhausts for my 117" build?
The last part of the puzzle is the exhaust....

The M8 softails seem very exhaust sensitive, and I don't want to mess up my build with a poor exhaust choice.

I'm currently looking at the Supertrapp Fatshot 2-1 with an open end cap.
Thanks

[VernDiesel]

Ridgid I don't have specific power goals. Mostly plan was to get more out of what I have and make sure its a reliable blast to ride. I want to get rid of my SE Pro tuner for various reasons and move to PV or other. Get rid of the catalyst in my pipe so that I could get more through it without it becoming a hindrance. So I was going to step up the cam, port the intake, bigger injectors, upgrade the compensator to make it more bulletproof and re tune it. Thought maybe 133 HP for a 15 HP bump would be achievable and that maybe I would be satisfied with that at least for a few seasons.

Plan on doing a leak down test and check crank runout. Make sure she is healthy. If leak down test wasn't great we could freshen it with hone & re ring and or do valve work if needed. Then you showed where I  can actually take those heads to 4.180. Get better pistons better rings more compression for not a lot of money and not a lot more work. But at that point with heads already off I'd probably get the heads done. Not sure what this combo could make. Perhaps 140 HP.

If instead I buy jugs, pistons to match, for big cubes big power (150 HP) I would also likely need to buy exhaust. The bike is recreation and just has to be fast fun & reliable. So I was just trying to pick a semi economical & sensible way of doing that.

"Ward ported heads/TB, 11.5:1CR, Georges cam, 64TB, 145+TQ 130+HP should be in the neighborhood (after proper tuning).  Are you talking about a 120ci with the F35A?  Lots of torque little HP?



Adam sorry I don't want to hi jack your thread. I've liked the S&S pipe for this displacement & power level.  Interested in what others suggest. 

[Adam76]

Adam sorry I don't want to hi jack your thread. I've liked the S&S pipe for this displacement & power level.  Interested in what others suggest. 

Yes, the S&S pipe seems to be the one that I see people use the most, with good results. 

I'm just looking for other good options, because I'm not a huge fan of the pipe for my particular bike.

Cheers

[JSD]

Adam the short TB types give away a bit off torque and are noisy enough to get the WA fun crew on ya arse. My mate has on on a lowrider S we wrapped the baffle with glass pack from KTM but its still loud. 

[Adam76]

Thanks JSD, I was never considering a TBR short 2-1 pipe.....

Think I'm going to end up with the S&S superstreet or possibly the Supertrapp Fatshot 2-1 which my local tuner likes quite a lot.

Don't think I can go wrong with either of these 2 pipes.
Cheers

[To The Max]

A.P.E. are making very good  torque and hp curves with the superstreet on big bore builds and they arn't noisy

[Adam76]

My CP 4.125" pistons arrived today.  Will drop them off to the machine shop with the cylinders sometime next week.

I'm going to mock it up and measure deck height and trim the base of the 114" cylinders in going to use.

But out of curiosity, how far are you guys finding the factory pistons down the hole on a stock 114" motor?
5 thou?  10 thou?  More?

[Adam76]

M8 114" Cylinder base gaskets -

Cometic Gasket CG-C10242-010 0.010" Thick Cylinder Base Gasket
OR   
Cometic C10177-010 .010" Rubber Coated Steel Base Gasket Set

Which gasket is the way to go for my M8 build?  I didn't realise Cometic did 2 different types. Priced differently too.

Thanks

[kd]

M8 114" Cylinder base gaskets -

Cometic Gasket CG-C10242-010 0.010" Thick Cylinder Base Gasket
OR   
Cometic C10177-010 .010" Rubber Coated Steel Base Gasket Set

Which gasket is the way to go for my M8 build?  I didn't realise Cometic did 2 different types. Priced differently too.

Thanks

FWIW, the rubber (micro) coated steel gaskets are excellent and the .010" thickness will be exactly that under compression when torqued.

[Adam76]

Thanks kd.