Static compression with a cr 460 and a 120" suburban kit.

[msnyder]

    This is a technical forum!  I need some tech advice.  Have a RGU M8 and would like to use a 120" kit and the Cycle Rama 460 cam. I want the torque to the left as much as possible. I know that caution must be exercised re: the CCP. I don,t want to get into trouble with pre ignition/knock.   The standard suburban kits have a static 10.9 CR.  Not sure what the factory CR. is?  Already running free flowing head pipe and crossover, CVO mufflers with fulsac 1.75" cores with his screens and wrap, SE. oval air cleaner and TTS tuner. Will have Brandon (J&B perf) do the tune when done. Would also like input on possibility/effectiveness of using thicker head gaskets (available?) to shave a little compression off.  The kit comes with .040 gaskets.  Some sharp people on this forum. Would appreciate some constructive advice very much.   Max

[BigT]

I had placed a call to CycleRama and talked to Wes. He recommended not to run the 460 in a 117" at 11:1. The problem is some of the cam developers are keeping the cam timing numbers secret making it it difficult to plan your build. I tried to get the intake close numbers for the TTS 200 cam and was told "the cranking compression would be less than stock". Then was told he was seeing stock numbers in the high 230s which is hard to believe.

[Ohio HD]

You can get some advice as to the standard compression ratio that some are seeing. But I would strongly advise cc'ing the heads to see what you have. Measure the piston height in the cylinder, then figure the compression ratio with the thickness gasket to be used. Also a thicker head gasket is not always desirable as it increases the piston squish. In the end you really need to measure to be certain you have what you want for the cams. As far as desired compression ratio, I'd be speaking to J&B as to what they think is best, seeing they'll be tuning the bike.

[rigidthumper]

I've seen reports of 240 with the HD TQ cam in a 114 stage 3 kit. M8 cams close sooner than TC cams, and the dual plug helps. IIRC, the CR460 has an intake close of 20°, with static of 10.9, CCP will end up at least 230.

[msnyder]

   Thanks for the replies.   I talked to wes @ cycle rama Monday.  Great guy and very helpful. And busy..He did not say "don,t do it". But as he was so busy he could not calculate what static compression would be acceptable.
He said someone (I think)  in Australia had already done what I propose to do. The guy told Wes that "it will pull your arms out of the sockets, it,s a beast". Sounds good to me.  Wes said he got 215# ccp with the stock cam and 205# with the CR460.  So in that respect it slightly lowers the pressure on a stock set up. Yesterday I got 230# on the front and 220# on the rear. "stock 107"  Axtell does the 4.125" pistons.  High $........The 120 needs the 4.185" I believe i read the m8 heads are 89cc but I,m not sure that if if comes down to taking away material it might be better to take it off the pistons.....Why am I the first? and usually the "the only one that ever happened too!"  I have the twin cooled heads and live and ride between 2500 and 6000 feet elevation. 
( slight offset on the compression and cooler too). I try to research and properly plan. Your input is much appreciated. Can anyone access and use a "engine calculation program" to figure out how this combo would play out?  I,m talking about CCP..  the 10.9  pistons 120 ci and cr460 cam.  Bad thing is I don,t think the specs are available for that cam.  And for good reason I suppose.  He has a winner and others would and eventually will copy (with minor changes) his work and design.. Thanks Max
'"

[1FSTRK]

Use this link, You can input all you numbers and it will give you what your looking for even though it was made with Twin cam base numbers.

http://www.bigboyzcycles.com/TwinCamComp.htm

[msnyder]

  Thank you for the link but there are to many missing numbers....cr460 not listed and technical details on piston ring configuration,deck height....I appreciate the help....Seems like by now there would be more builds out there (m8) similar to this..I know Wes @ CR also builds motors...Maybe I,ll email him and see if he can do a  a calcalation re: best static compression ratio and expected ccp.  Any other suggestions or  builders with ideas please chime in... Thanks .. Max

[kd]

That calculator should work for you too. You have to enter all the numbers when a cam is not listed. Not knowing the ring height will be a very minor discrepancy. For head gasket bore size add .040 to the cylinder bore as a close guess. The deck height is something you will only know by removing the heads and measuring it. Use 0 for a start and you will have an average compression figure. If one of the builders on here has had a few apart and has noticed a pattern for M8 deck height they may see this and offer their thoughts. Hopefully Wes will hear your plea and give you the specs you need to use the Bigboyz calculator if you ask him. 

[1FSTRK]

Most of the missing numbers are here on the forum in different threads if you just search around.
The only cam number you need is the IVC and Robin gave that in reply 3 here.

[DTTJGlide]

I'd think about running the CR450 instead, it has a IVC of 25 which would help lower CCP a little. Durwood (Daren) tested the 450 on a stock 107 & it only showed slightly less left side tq, I would think with the added CR & CI you would have plenty of low end tq.

[Durwood]

CCP on my bike stock was 215/215, with the CR-450 it was 202/202 and with the CR-460 it's 205/205, this is with the 10:1 compression that the 107 has in stock configuration.

To answer the OP question, yes, you could run either of the CR bolt in cams at 11:1 but I wouldn't. I think that 10.5:1 is plenty for these cams.

I have a friend down under that installed a Cycle-Rama 460 in his otherwise stock 2017 CVO 114 which is 10.5:1, and he told me that it feels like it's pushing his eyeballs against the back of his skull when he twists the wick..Lol

He street tuned it so there is no graph, but just his expression over the phone was enough for me...I am looking forward to the CVO's coming in and getting one of these installed and tuned.

[msnyder]

  Thanks to all for the responces and suggestions. And Darin the suburban kit is advertised at 10.9:1.. I will talk again with them and see if it is possible to get the kit with a lower CR.  Perhaps a upcharge and a wait.  If I had to "guess"  (not technical) I would have said 10.4-10.5;1 also.... And i think the guy you mentioned with the 114 is the same guy Wes was talking about.  I decided to check the existing ccp. and got 230#ft and 220# rear Cyl.
Leak down test results were 2 % frt. and 4% rear.  I could take the easy way out and just do the cam and tune but I am reminded of what Herman Melville said.  "It is better to fail at originality than to succeed in imitation".
   Will look forward to your further suggestions and help. Max

[Mainecat]

If I'm not mistaken, I believe the TTS-200 was designed for 10.5-11.0:1 CR.  I run it in a 114" and it holds the left side well.

[BigT]

If I'm not mistaken, I believe the TTS-200 was designed for 10.5-11.0:1 CR.  I run it in a 114" and it holds the left side well.

I just installed the TTS-200 in my 117" at 11:1 and should have it fired up this weekend. I'll post the cranking compression.  It will be a several weeks before I get it tuned and can post the results.

[Mogollon]

    This is a technical forum!  I need some tech advice.  Have a RGU M8 and would like to use a 120" kit and the Cycle Rama 460 cam. I want the torque to the left as much as possible. I know that caution must be exercised re: the CCP. I don,t want to get into trouble with pre ignition/knock.   The standard suburban kits have a static 10.9 CR.  Not sure what the factory CR. is?  Already running free flowing head pipe and crossover, CVO mufflers with fulsac 1.75" cores with his screens and wrap, SE. oval air cleaner and TTS tuner. Will have Brandon (J&B perf) do the tune when done. Would also like input on possibility/effectiveness of using thicker head gaskets (available?) to shave a little compression off.  The kit comes with .040 gaskets.  Some sharp people on this forum. Would appreciate some constructive advice very much.   Max

The 120 ci engine you are building is an excellent combo for a large displacement M8 engine during early 2018. However, you may be attempting to pound a square peg into a round hole by using too-short of cam.

The CR460 cam is an excellent cam that has great reviews, but it is primarily designed as a bolt-in cam for a 107 ci engine. Yet, you are building a relatively high-dollar 120 ci engine. Why install a cam primarily designed for a 107 (or maybe a 114 ci engine) when building a 120 ci? Yeah, I know, you're worried about the infamous "left side" of the curve.

Ideally, you should want to build a "happy" engine, an engine with compatible parts, parts that have the proper relationship to one another. The CR460 cam, or any cam with similar specs, will typically result in a "John Deere tractor" style engine that typically runs out of air early on a big 120 engine. Why spend all the money building a 120 ci engine to do that? The large displacement alone is going to give you tons of torque. Just a thought, mind you.

Anyway, following are the specs for your 120 ci engine that were run through the Bigboyz calculator for two different cams:

Cycle Rama CR460 bolt-in
T-Man M8-216-2 PS bolt-in

FYI: Personally, I don't have any dog in this race, so I don't have any hidden agenda, and I don't sell any parts or services. I just thought it was an "interesting and popular motor build" to document, and thought some "insight" might take much of the "guesswork and unknowns" out of the project --- nothing more, nothing less!

That said, I chose the T-Man 216 cam because I believe it is one of the better choices "currently" available (but surely not the only cam, and I can't comment about cams with unknown specs) for the 120 ci engine that you want to build. In another year or so, there will more cams available, so if you don't like the 216, you should be able to quickly change it out in 4-6 hours in your garage. After all, you will have already built this engine once before, so you know the ropes. I assume you are building the engine yourself. Is that correct?

Anyway, following are the calculator numbers used:

Following are the specs used for both cams:
Bore: 4.185"
Stroke: 4.375'
Rod: 8.015"
Head Gasket: .040"
Cyl deck Height: .000"
Piston Dome Volume: -1.2 cc   (for Suburban M8 120 ci Mahle piston)


Following are the assumptions made:
Cyl Head Combustion Chamber Volume: 87cc
Apparently, M8 chamber volume is varying between 85cc and 89cc, so the difference was split. I've heard of some chambers measuring as low as 82cc, but I consider them an anomaly.

Any ring land volumes were ignored, so zero was used.

Since you typically ride between 2500' and 6000' above mean sea level, the difference was split and 4200' was used.

Since neither cam was run through a Cam Doctor, the advertised published specs for Intake Valve Closing (IVC) for both were used:
20.0 IVC for the Cycle Rama CR460
27.0 IVC for the T-Man M8-216-2 P


Output results for the Cycle Rama CR460 cam:
Static Compression 11.13:1
Engine Displacement:  120.36 ci (1972cc)
Intake valve Close ABDC: 20.0
Corrected Compression: 10.90:1
Cold Cranking Compression (CCC): 208.1 @ 4200' above mean sea level


Output results for the T-Man M8-216-2 PS cam:
Static Compression 11.13:1
Engine Displacement:  120.36 ci (1972cc)
Intake valve Close ABDC: 27.0
Corrected Compression: 10.72:1
Cold Cranking Compression (CCC): 203.7 @ 4200' above mean sea level


Following are some other key thoughts you might consider:
The "calculated" CCC numbers with both cams are in the ballpark of what others have listed for various M8 engine combos, so your low-end torque should not suffer. And with the M8-216-2 P cam, the engine will not run out of air upstairs.

The CR460 cam lists 206 intake duration, 226 exhaust duration, .460" and .440" lifts, 6° overlap, and a 106° LSA.

On the other hand, the M8-216-2 PS cam lists 216 intake duration, 236 exhaust duration, .475" lift on both sides, 18° overlap, and a 104° LSA.

The increased duration, greater overlap and tighter LSA with the M8-216-2 PS cam will benefit your 120 ci engine. I'm more of a quarter-mile guy, so if this were my engine, I would probably install the larger T-Man 226 PS cam (or similar cam) and bump the compression up a tad, but the smaller 216 cam is better suited to your riding style.

As an aside, I only consider cams with published specs. And I've even seen some published cam specs that are flat-out wrong! Nevertheless, no serious engine builder worth his salt would install a cam without first knowing the specs. That's why most top automotive engine builders and even some Harley builders invest in an expensive Cam Doctor or EZCAM measuring device to verify cam specs. And they also degree the cam while it's in the engine to verify the installed cam meets the intended cam specs. NHRA's John Force would not install an unknown cam into one of his engines, and neither should you. In fact, without knowing certain cam specs, we could not have calculated the following specifications.


The Suburban M8 120 ci piston's advertised compression ratio of 10.9:1 was calculated assuming the piston is about .020" down in the cylinder. Most OEM M8's come with the piston between .015" and .025" down in the cylinder. And most SE114 cylinders are too long for an optimum "zero" deck height. A shorter cylinder providing a zero deck height will improve these specs. Consequently, it is unnecessary to worry about ordering a special piston kit with lower compression.

It's not wise to just slap together a large displacement "kit" engine. Anyone can do that, and many builders are doing just that! Instead, it's better to blueprint the engine correctly and build a "happy" engine with the proper relationship of parts instead of just building an average run-of-the-mill engine. Moreover, you can't assume what the stock or kit engine's deck height or combustion chamber volume is. Nor can you assume that your cylinders are straight, round and not tapered without first checking them. In fact, I'll bet the static compression ratio of a stock OEM M8 engine is roughly 0.3 points "less" than Harley's advertised compression ratio for any given engine model. Inaccurate assumptions result in underperforming engines. As such, I recommend doing the following:

Mock up your engine and measure piston deck height. It will be probably below "zero" deck height. If necessary, deck the cylinders to achieve zero deck height. That will maximize static compression while giving you a good .040" squish with the Cometic head gasket. I would use the .040" Cometic head gasket.

Use a burette and cc the head's combustion chamber to verify the volume. Ideally, for this street engine, I'd shoot for 85cc to 87cc. Within limits, you can deck the head to reduce chamber volume.

I don't think you mentioned the heads, valve springs, lifters, pushrods, TB, injectors, clutch, and clutch springs you are using. Today, the most economical way to build an M8 120 ci engine is to buy the SE Stage IV kit for about $2600, and eBay the parts you don't use and any used parts. Your used 107 heads are worth $300-$400 and the used OEM 55mm TB about $100. That alone will recoup some of the $2600.

To build a 120 correctly today, you'll need the SE64mm TB (prefer the HBI 62mm, but it's costly), 5.5g injectors, hi-performance lifters, adjustable pushrods, extra-plate clutch, and hi-psi clutch springs.

Even though both cams are bolt-in, high-performance valve springs are a "wise" investment, and the springs come with the Stage IV CNC heads. The SE CNC heads, although not optimum, should improve over the stock OEM castings (and you can sell-off your stock castings). And regardless of what some say, ported stock head castings also work well. I would disassemble the new CNC heads and match the valve stem height for each pair of valves and make sure the valves seal properly.

Considering all of the engine oil sumping problems that some M8 owners are plagued with, it would be wise to get the latest version of the MoCo's sumping Service Bulletin M1450 and closely review it for procedures. The latest revision that I know of is dated 11/15/17, but there may be a more current version or a new one about to hit the streets. Follow the procedures closely for installing the oil pump and cam plate. If you don't already have them, getting service, parts and electrical manuals for your model bike would also be worthwhile.

You'll have to make a "management decision" about upgrading your oil pump. According to SB M1450, dated 11/15/17, the MoCo recommends upgrading to the latest pump for any engine built prior to 10/10/17. Yet, I've seen some engines running without oil sumping using a much older revision of pump: it could be the riding style, the cylinder blow-by or lack thereof, the clearances, the pump, the installation. Go figure! A full-compliment inner cam bearing is also recommended. George's Garage makes a nifty anodized bearing puller.

Be sure to check the torque on the piston oiler screws. The MoCo increased it from early-builds. Some screws have come loose, and some screws are too long for their threaded hole. Make sure the screws don't bottom in the hole. Cometic offers a highly recommended updated gasket set for the piston oilers.

With the high-torque 120 motor, I would use the SE extra-plate (10-plate) clutch with an AIM VP SDR Variable lock-up. For starters, I would also use either Harley's 1200N (white stripe) or 1275N (red strip, higher psi) clutch springs, depending on whether the dyno report shows any clutch slippage and how strong of pull your clutch-lever hand can handle. AIM has even higher psi, #360, clutch springs. Your stock M8 RGU clutch springs should be the wimpy 1100N springs, which have less psi than the 2014-16 Rushmore springs. I "think" the 1200N springs come with the SE Stage IV kit. A set of three 1275N clutch springs are about $28 from the MoCo.

The Fullsac free-flowing head pipe and 1.75" cores will work OK for max low-end power, but I would also try Fullsac's 2.0" cores with this engine. Call Fullsac and ask for some 120 dyno charts using 1.75", 2.0" and 2.25" cores.

Finally, locate a knowledgeable dyno tuner who knows the TTS tuner well and get a good dyno tune. On average, that should give you between 130 and 135 HP and similar torque readings (SAE, 5th gear) on pure pump gas (no tricks). Using stock heads and TB should drop the numbers roughly 5-10 points. Note that 6th gear dyno runs are usually 2-4 percent higher than 5th gear runs.

This isn't the only way to build a 120 M8, there are many ways to slice an apple, but it is a sound and reasonable way to do it. These tips should take much of the "guesswork" and mystery out of building an M8 120 engine and should save you a bunch of time. And in the future, if you are unhappy or bored with it, one can always spend their "retirement fund" dyno testing cams with "unspecified" specs.

[kd]

Wow, great 1st post Mogollon.    Very well written and comprehensive.  Welcome to HTT and please stay around. 

[msnyder]

  Thanks for that very thorough reply and the advice Mogollon!
   To clear up a couple of things...Yes I intend to do the work myself. Just received the m8 cam install plate from Georges.  Very nice addition to the twin cam kit.  Plan on Stock heads,(would welcome spring suggestions) had hoped to use a bolt in cam and avoid changing springs but I think I read anything over .460 lift is risky.. Have looked at lifter options including offerings from Larry,s. His 842 series, Hylifts maybe The S&S.  i have a set of SE adjustable pushrods.  I want to use the stock TB and injectors and see how that works. I ordered a set of the clutch springs for a 2015 CVO. (100 lbs rating).  I ordered the " latest and greatest oil pump of the month" from the dealer.  Would like a link to the "updated oil pump installation procedure". I,m thinking I read that is is one somewhere....... Of course I have the M8 service manual also.   I talked again with Jason @ Suburban and he gave me some tips and thoughts. Great guy!   He told me verbatim what you did re: the piston oil jets... 115 YEARS and making sloppy mistakes on simple things like that?  Yes Cometic--Cometic.
  Lastly I,m planning on having Brandon  at J&B Performance (Greenville TN.area) do the tune with my TTS.
Thank you again for all the advice time and tips you have given me. Look forward to any and all helpful replies.
                                                                                Max  (still focused on the left side)

[Mainecat]

If you do not go with the SE stage kit, I would recommend the cheaper S & S lifters.  I recently swapped out cams in my stage 3 and they are quieter than my SE's were.

[badcooky]

If you do not go with the SE stage kit, I would recommend the cheaper S & S lifters.  I recently swapped out cams in my stage 3 and they are quieter than my SE's were.

Good to know bro.

[HD/Wrench]

As a shop I do not think its a mistake to use a small cam in a large engine.. What are the goals of the build ?   I  have the 120 parts coming back today from powder coat and D cut. plan to run a rather small cam as the objective is making massive amounts of tq. Rider does not care what it does over 4500 so give him what he wants .

Cam IVC is 24 on this build , stock heads stock t/b larger injectors . Will be no Hp queen for sure but power on tap in the normal riding range will be impressive for sure

[badcooky]

As a shop I do not think its a mistake to use a small cam in a large engine.. What are the goals of the build ?   I  have the 120 parts coming back today from powder coat and D cut. plan to run a rather small cam as the objective is making massive amounts of tq. Rider does not care what it does over 4500 so give him what he wants .

Cam IVC is 24 on this build , stock heads stock t/b larger injectors . Will be no Hp queen for sure but power on tap in the normal riding range will be impressive for sure

Good point man.

[Mogollon]

  Thanks for that very thorough reply and the advice Mogollon!
   To clear up a couple of things...Yes I intend to do the work myself. Just received the m8 cam install plate from Georges.  Very nice addition to the twin cam kit.  Plan on Stock heads,(would welcome spring suggestions) had hoped to use a bolt in cam and avoid changing springs but I think I read anything over .460 lift is risky.. Have looked at lifter options including offerings from Larry,s. His 842 series, Hylifts maybe The S&S.  i have a set of SE adjustable pushrods.  I want to use the stock TB and injectors and see how that works. I ordered a set of the clutch springs for a 2015 CVO. (100 lbs rating).  I ordered the " latest and greatest oil pump of the month" from the dealer.  Would like a link to the "updated oil pump installation procedure". I,m thinking I read that is is one somewhere....... Of course I have the M8 service manual also.   I talked again with Jason @ Suburban and he gave me some tips and thoughts. Great guy!   He told me verbatim what you did re: the piston oil jets... 115 YEARS and making sloppy mistakes on simple things like that?  Yes Cometic--Cometic.
  Lastly I,m planning on having Brandon  at J&B Performance (Greenville TN.area) do the tune with my TTS.
Thank you again for all the advice time and tips you have given me. Look forward to any and all helpful replies.
                                                                                Max  (still focused on the left side)

Using your stock heads and TB on the 120-build will produce an excellent engine. The smaller intake will keep air velocities up and improve the low-end "left-side" torque, which is what you want. Keep in mind, though, that all engines are torque engines. The only difference between a so-called torque (left-side) engine and a horsepower (right-side) engine is the rpm at which the engine makes torque.

If this was my engine, I would install high-performance valve springs regardless of whether I use a bolt-in or non-bolt-in cam. The reason you heard that it's risky to have any valve lift over ~.460" lift is because stock M8 valve springs coil bind around .515" lift. Subtract .040 to .060" spring clearance, and you are now down to a max valve lift of .475" to .455". Additionally, stock valve springs will often start sagging earlier (less mileage) than high-performance springs, resulting in valve float or worse. So I'd spend the extra $270 or so for the high-performance springs. The HD SE valve spring kit should work well for you up to about .520" lift.

Regarding lifters, there are many options, but I haven't tried all of them. You might ask some of the posters on this forum about their experiences. That said, I prefer American made lifters instead of those made outside of the US. My experience is that they hold up better but typically cost more. However, over the years I've seen even the best lifters fail. I've used S&S Premium lifters, which are American made, with good success. I don't "think" the S&S non-premium lifters are American made.

Recently, a friend of mine installed a set of high-performance SE Stage IV lifters into an M8 114 ci motor that dynoed at roughly 130 hp. What caught my attention was that during pushrod adjustment, the lifters bled down rather quickly. And prior to installation, the lifters were pressure-primed with oil. Currently, the engine is running great and sounds quiet, but it doesn't have a lot of miles on it. That's all I can say about the M8 SE lifters.

To reduce costs some engine builders have used Chevy small-block lifters in TCs and M8s. These lifters will fit; roller and body dimensions are the same. However, I don't recommend them because their internal hydraulics and oil flow characteristics are quite different than Harley lifters.

I'd recommend installing high-performance valve springs and doing a quality valve job on your heads. Your head castings are now "seasoned," so their dimensions should be set. As such, I would have a professional head porter check all the head parts for any excessive wear, then touch up the valves and valve seats, and match valve stem heights. These procedures will go a long way towards building an excellent sealing pump.

The internal combustion engine is nothing more than an air pump. To build a "happy" engine, you need an excellent sealing pump, the right combination of parts, and proper assembly procedures. Excellent cylinder sealing is key to making power. The heads and valves are the top-end of the pump while the cylinders, pistons and rings are the bottom half. A top-notch valve job includes good valve guides, solid seats, and concentrically matched valves and seats. If you need to replace any of the valve guides, replace them all with aftermarket magnesium bronze "tapered" guides, which will slightly improve airflow.

Make sure the cylinders are finished round, straight, not tapered, and with the proper finish for the ring pack. Be sure the rings fit in the piston ring lands properly and rotate smoothly. Check ring clearances in the piston ring lands and end gaps in the bore. Also be sure to space the ring end gaps properly during cylinder installation.

As an aside, you've probably noticed that 107 ci TC engines are in vogue. The four additional cubic inches offer big "bragging rights" over a measly 103 engine. Yet, the problem with some 107 engines is that the cylinder spigots are so thin that the cylinders are moving all over the place duration operation, and cylinder sealing is often poor in 10k miles or less. But the owner often doesn't understand that. Not only is power down, but the cylinder blow-by can contribute to wet-sumping. I'll take an excellent sealing 103 ci TC engine any day over a poor sealing 107 ci engine. That's just me. YMMV!

You'll probably need the 5.5g/s injectors, but starting out with stock injectors is OK. Your dyno tuner should know when the injector's duty cycle is maxed out, so let him make the call.

Regarding your "latest and greatest oil pump," I wouldn't worry about it. Go ride your bike and have fun. Until the MoCo provides a definitive fix for the sumping problem, oil pump versions are a crapshoot. Checkout your new pump for cleanliness and any burrs while keeping the gears in the same position they were shipped in, then install the pump following the latest MoCo instructions. Make sure the pump doesn't bind when rotating the motor. And don't forget to check the piston oiler screws. After that, go ride the bike and don't worry about it. If the engine eventually sumps, you'll have to pull the engine apart and just deal with it.

However, don't be tone-deaf to oil sumping while riding your new motor. Pay attention to any sudden large power loss. If you do encounter a loss, pull over to the side of the road and let the engine idle for 5-10 minutes to see if that "temporarily" scavenges the crankcase of excessive oil. You don't' want to make things worse and burn up your crankshaft and rod bearings during an extended period of oil sumping. Of course, that would provide the perfect excuse for installing the M8's 4.5" stroker crank.

I should be able to track down a link to the latest SB M1450 (dated 11/15/17 or later). Or maybe other forum members already have a link. If so, post it!

As far as cams go, I've already stated my philosophy. Simply put, you can't understand why a cam is working or not working unless you can compare its specs to a dyno chart or racetrack performance. And you can't identify trends. As such, it will be difficult making an "educated" decision about which direction to go when making cam changes.

Additionally, when selecting your cam, any cam lift differences are not really important for this level of engine build, assuming your valve springs are sufficient for the valve lift. The important cam specs are opening and closing timings (primarily intake closing and exhaust opening), duration, and overlap. Some cams lift faster than others, putting more "area under the curve." But there is no way to determine this unless you degree the cam, and that is overkill for this level of engine.

You might consider calling the major M8 cam manufacturers offering cams "suitable" for a 120 ci motor and ask them the following: what cam do they recommend, why, what is their rationale, what compelling reason can they give you for installing their cam? Also, note any cam pricing differences. Make sure any dyno chart comparisons use the same correction factor and tranny gear, and hope no tricks were played, like running no A/C or playing with dyno sensor location or temperatures. Then make your cam decision based on your priorities and feedback. As I've previously mentioned, my philosophy is not to install cams that I don't have specs for. But that's just me; it's one of my pet peeves.

Anyway, by paying attention to details, planning things smartly and having patience, you will end up with an excellent engine. It's worth taking the time to cc the combustion chambers and shorten the cylinders (if necessary) to optimize the CR. Eventually, I would also test Fullsac's 2.0" muffler cores. And in the future, it should be easy to install a larger TB, higher flowing heads, or a different cam.

Lots of luck. It should be fun riding your bike through the Appalachians this summer.

Cheers

[HD/Wrench]

Have used the fulsac kit it works very well .

https://www.sscycle.com/tappet-cuffs/
Lifters flavor of the month , S&S is offering a low cost billet lifter anti rotation block . Nice upgrade .

Valve job nothing wrong with that either .  At and at that point I would at least do a minor blend in several areas as these are stock heads with core shift and many have material hanging into the port .  nothing crazy by any means something that you can do your self or have the head porter " clean them up" I do not want to use the term porting as well just me I guess.   As I said I am in the process of putting that 120 together ow.. I wanted to so badly clean the ports up but .. cannot as I want to see how it works as a stock head . Testing an testing

Check the oilers to see if they are loose , there is a small trick there as well but it may or may not be the total reason for sumping in some engines .    Case pick up is most likely a larger reason . But will have to see where this goes from HD as well .


In my opinion the OEM springs are fine for lift up to the 460 range . SE offering of springs at this point is a good price point .  or this option in the very close price point as well  https://www.sscycle.com/products/heavy-duty-valve-spring-kit-for-2017-18-m8-touring-models/

[1workinman]

Wow, great 1st post Mogollon.    Very well written and comprehensive.  Welcome to HTT and please stay around. 

very good advice given there especially not just bolting the parts together . again well written

[mike jesse]

My 2 cents on the piston oilers.

Every case I've touched does not have a chamfer on these holes. This "may" not allow the oiler to sit flush onto the case.

It takes all of 2 minutes to touch those 4 holes up with a 90* chamfering tool.

Do it.

[HD/Wrench]

That and the screws are self tapping so you may have tq on the screw but do you have clamp load on given part

[Sunny Jim]

Given the suburban kit is set at 10.9:1 , how does it compare with other available kits eg. Fuelmoto, Tman?

[happyman]

Have used the fulsac kit it works very well .

https://www.sscycle.com/tappet-cuffs/
Lifters flavor of the month , S&S is offering a low cost billet lifter anti rotation block . Nice upgrade .

Valve job nothing wrong with that either .  At and at that point I would at least do a minor blend in several areas as these are stock heads with core shift and many have material hanging into the port .  nothing crazy by any means something that you can do your self or have the head porter " clean them up" I do not want to use the term porting as well just me I guess.   As I said I am in the process of putting that 120 together ow.. I wanted to so badly clean the ports up but .. cannot as I want to see how it works as a stock head . Testing an testing

Check the oilers to see if they are loose , there is a small trick there as well but it may or may not be the total reason for sumping in some engines .    Case pick up is most likely a larger reason . But will have to see where this goes from HD as well .


In my opinion the OEM springs are fine for lift up to the 460 range . SE offering of springs at this point is a good price point .  or this option in the very close price point as well  https://www.sscycle.com/products/heavy-duty-valve-spring-kit-for-2017-18-m8-touring-models/

curious  about the term case pickup.     can you help me out a little hopefully  Thank

[VDeuce]

Given the suburban kit is set at 10.9:1 , how does it compare with other available kits eg. Fuelmoto, Tman?

Fuel Moto would not provide me with piston dome volume.

T-Man's 120 pistons have a 6CC dome, cutable. So it all depends on where the heads are. If we assume 89CC heads, a 6CC dome will be very high on compression, about 11.7:1 static and over 240CCP and I would need to cut them down to the point that may as well use a flattop, which is what Suburban offers.

T-Man's setup seems geared toward his heads which have larger chamber volume.

[BigT]

I bought a set of M8 Wiesco 11:1  4.125 pistons from Tman. Flat top -4 cc. I thought he offered the same piston at 4.185 / 120".  Cranks over at 218 F&R with the TTS 200 cam.

[VDeuce]

I bought a set of M8 Wiesco 11:1  4.125 pistons from Tman. Flat top -4 cc. I thought he offered the same piston at 4.185 / 120".  Cranks over at 218 F&R with the TTS 200 cam.

That I will check on Monday, thanks! The website lists flattops for the 117 version, but I would want them for the 120 bored cylinders.