deck height measured over the pin differant side to side?

[1340evo]

Anyone had this, I can't find a spec. in the manual but its ".005 differance on the front cylinder and ".006 differance on the rear cylinder?
Although looking at the pistons, they are contacting in the bores at 12 and 6 ??

[Ohio HD]

No spec that I know of.

But now all you have to do is figure out is the crank out of squire to the deck, are cylinders not parallel top to bottom, the piston bin bore not parallel to the piston crown, bent rod, rod big and small ends not parallel to each other. Also is the difference the same at the piston when at the bottom of the bore.

So, 0.005"? I wouldn't even be concerned unless you can verify that the piston skirt isn't parallel to the bore during it's travel top to bottom of the cylinder. The piston crown only needs to not hit anything. Of course if you find out it's the piston crown, then you only need deck the piston square to the pin bore.

[1340evo]

At the bottom, best I can do is square the ends of the old pins in the lathe, put a bolt through them both and bolt them together in the small ends to get them straight  it slides through so guess it's in-line. But at the bottom, because of the clearance in the bearings and the length of the rod, it shows fine to the machined surface.... ??

Just put a piston in the bore off the engine, and I can get about .008 pushing it side to side.. but its hard to measure?, measure at 90 deg to this over the thrust faces and it hardly moves anything.

[Ohio HD]

To blue print a motor you have to start at the beginning. Otherwise you're just working through all of the factory tolerances and wear that the miles created.

[kd]

I don't think putting the gauge block on the piston is the best way to measure. If you use the cylinder deck for the block it will be a more true surface. Measure both sides and see what you get. Expect about .001 or so. It probably won't be perfect.

[SP33DY]

I check the rods for straightness at the crankcase deck using a long gage pin.

I got them from Vermont Precision Tools. 0.7910" x 6.500" for Evo, and earlier engines,  0.9270" x 6.500" for TC and M-8.

[1340evo]

To blue print a motor you have to start at the beginning. Otherwise you're just working through all of the factory tolerances and wear that the miles created.

The bottom end has just been re-built with all new bearings, so should be right.

I've tried it both ways with the stand on the piston measuring the deck, and with the stand on the deck measuring the piston.. same both ways...

[Ohio HD]

To blue print a motor you have to start at the beginning. Otherwise you're just working through all of the factory tolerances and wear that the miles created.

The bottom end has just been re-built with all new bearings, so should be right.

I've tried it both ways with the stand on the piston measuring the deck, and with the stand on the deck measuring the piston.. same both ways...

I think it was T-Man that stated in an article, he never saw a factory crank shaft bore to deck surface in a Harley that didn't need to be corrected. So just putting bearings in a motor only puts it back to the factory tolerances at best.

You can check the rod against the deck as SP33Dy said, But it only gives you that measure of one degree out of a 360° rotation of the crank.

As KD stated, there will be some variation, and the measuring technique is crucial to getting it right. The cylinders need to be bolted to the case, and a solidly attached indictor mounted on the cylinder as the fixed surface.

Also if the crank isn't trued correctly, you'll see issues with parallelism.


[attach=0,msg1384853]

[1340evo]

yes, I think you ar right. Using plastic pipes to hold the cylinders down is not working. Also putting the gauge on the pistons not the best as they are not exactly flat.
I'm off to make some Ali spacers and a better gauge mount so I can do it like you show abouve.
I've just re-done it from the cylinder top and did get it out side to side, but only by .003

will get some better gear made first....

Put this post on hold

[kd]

The plastic fittings are OK to use. Tightened down is tightened down and the plastic has less chance of scarring the cylinder gasket surface.  Lots of us use the plastic fitting including me.  Some of us also made the tool like Ohio showed in his pic.  Most deck tools are large fur auto use and too bulky to fit the twin cam use.

[1340evo]

okay, checked from the top of the cylinder, it's just under .004 side to side differance on both... guess thats not bad ??

Has anyone ever checked both sides, or is it just me thats anal

[98fxstc]

I was about 0.004" side to side on my twincam when I did my rebuild
I had a Darkhorse crank which I checked at 0.0001" so I figured the crankshaft bore was not square to the deck but I would live with it   

[1340evo]

yes, they re-built my crank and measuring the pinion they said it was just in limit at .0015... TBH, I measure it better than that, but will have implication... mind you, its better than it was at somethink like .018 LOL

I've mailed them and see what they say.. its the best builder in the UK so knows what he's doing.. guess sometimes things are not made 100% in the first place ... I'm happy at 0.10mm especialy as it's rubbing up on the thrust faces and no where else...

[wfolarry]

I wouldn't worry about .005.
If you really want it to be less have the gasket surfaces cut. It's not unusual to see the liners move or the gasket surfaces not true on a motor that has some miles on it.

[1340evo]

I'm thinking is the rod end bent a bit as .004 over that distance, I'm sure it would bind up?

[Ohio HD]

You said a guy just rebuilt the lower end, and that he's the best builder in the UK. Wouldn't he have checked the rods for being bent while rebuilding the crank?

I think you're way over thinking all of this. You're most likely seeing the factory stack up of tolerances.

[kd]

If this builder is as good as you say he's probably a busy guy.  He also may record his measurements and could still have them.. The fact that the front and rear combustion chamber volumes match up with different deck and head CC measurements (remind him of that) makes more sense now.  I wouldn't be surprised if it was a purposeful calculation and the way he reached his goals without extra machining.

Like the others are saying, the tip in the deck measurement across the wrist pin could be engine case deck surface machining, case distortion, and line bore for a few. If it has performed without catastrophic failure up to this point, and the fact that both pistons have the same deviation, you could take the average between the left and right + & - measurements and use that for your quench calculation for  head gasket thickness choice and feel comfortable they are even in both cylinders. The valve pockets are front and rear so the only other concern may be the cam lift and valve size if you are changing them. I think it's great that you are doing all of this.  It is always best to check everything before assembly.  You will know what you have and be more comfortable with it in the long run.

[1340evo]

Yes, I'm sure he did and I'm sure you are right. He re-honed the rod bottoms, fit new pin, did bearings both sides and timing chest bearing. Balances and trued the crank to the pistons... I've mailed him so see what comes back... .004 may be what they work to??

He only did the bottom end and didn't assemble the cylinders as I wanted to paint them first. But he will have the measurements for sure.
Yes, its been with him 5 months!!

Also .004 on the top, becomes .0026 on the sides

[1340evo]

they think .004 is okay over the piston top?

Anyone else had experiance of this??

[jsachs1]

I'm thinking is the rod end bent a bit as .004 over that distance, I'm sure it would bind up?

If you're nervous about a bent rod. Use or make a mandrel wider than a wrist pin, with the same OD as the wrist pin. Install in small end of the rod. No cylinders on the case. Rotate the flywheels until the mandrel touches the case top. You can use thin feeler gauge strips under each side of the mandrel to see if its contact to the case top is equal. If NOT: than use a thicker or thinner feeler gauge to find the difference on the side in question.
If the rod is bent, you can straighten it easily. Look in the "Home Made Tools Section":. I think I have a picture of a rod straightener I've made back in the day.
John

[1340evo]

I'm thinking is the rod end bent a bit as .004 over that distance, I'm sure it would bind up?

If you're nervous about a bent rod. Use or make a mandrel wider than a wrist pin, with the same OD as the wrist pin. Install in small end of the rod. No cylinders on the case. Rotate the flywheels until the mandrel touches the case top. You can use thin feeler gauge strips under each side of the mandrel to see if its contact to the case top is equal. If NOT: than use a thicker or thinner feeler gauge to find the difference on the side in question.
If the rod is bent, you can straighten it easily. Look in the "Home Made Tools Section":. I think I have a picture of a rod straightener I've made back in the day.
John

Hi, thanks. I did that as I say above, but using the 2 old piston pins bolted together LOL.. it worked... ansd it was fine although you can kind of get it to read what you want due to play in the rod. The builder checked this also and said it was fine. He just didn't check at full stroke the other way?
At .004 he's saying there is no problem and to run it.. do you agree?

[jsachs1]

Short answer- Yes, it's a Harley. Mine, I'm anal, I'd straighten it, cause I can.
John

[1340evo]

Short answer- Yes, it's a Harley. Mine, I'm anal, I'd straighten it, cause I can.
John

Me too.... I have the old pin and two big screwdrivers that will go through the bore, but what does side loading the crank pin bearing do and can you damage it or the honed rod end?

[kd]

Remember that .004 across the top is .002 average.  Pull out your feeler gauges and check the .002 blade. 

Like John said, some of us are just OCD about this stuff.  Especially if building a close tolerance hard run engine. Unfortunately for me I fall into that category.   

[1340evo]

And .004 over the top is .0026 down the side due to the 3:2 piston shape, and then only 1/2 of it thats not given over to rings... so .0016 in all.. so not a lot, maybe running in will correct that LOL

But, does it make the rings run on a point in Stead of a face? 

[kd]

I know that crankcase halves sometimes are not perfect on the deck that the cylinders bolt down on.  That would cause a variance.  A straight edge may show that.  Also as a set of cases season it wouldn't be hard to believe the same deviance could occur.  A slight angle on the case deck over the length of a cylinder the tilt would grow at the other end too.  There are so many ways it can happen over time. 

[1340evo]

Decks are nice (except the bit where the engine builder has used a rod through the small end to torque up the cam gear and indented it!) but there is no way I can check how true they are to the crank.
Unless they caused this in the re-con, I have to assume it was like this before and it worked well then.

Need to calc squish but think I need .015 off each head which I can do this week, then weekend its back together

[Hillside Motorcycle]

Start by precision decking the cases, then insure the wrist pin C/L is perpendicular to the case deck, then both ends of the cylinders are machined to 90* to the bore C/L...............or assemble it and ride.
Then, the oil trapped in the flywheel balance holes??
Me thinks you are overthinking this.

[1340evo]

That's what I say, put it together and ride...
Need to work out the gaskets now..
My cc's are the same and squish is correct.... but what CR is best for a ev27 cam and how to work it out?

[kd]

I'm thinking around 10.5:1.  Some that have extensive background using that cam will be more helpful.  While you are waiting for a few answers try this calculator to see where you will be at with what you now know.

[rigidthumper]

That's what I say, put it together and ride...
Need to work out the gaskets now..
My cc's are the same and squish is correct.... but what CR is best for a ev27 cam and how to work it out?

EV27 has a 36° close, and I've found less issues setting the static CR to 9.5:1- can use the stock carb, and available fuel, any time, any where, without drama, and enjoy the ride. Add an adjustable ignition, if you feel the need.
Cometic .030" thick head gaskets, 74cc chambers, zero deck height, and Bob's your uncle

[1340evo]

Well, not a lot of gaskets available right now, but if I got a
.036 head and a .016 base, that gives me .052, on average the pistons are .010 high, so that would equate to a .042 squish.
My heads are 81cc...

What I'm working to is advice from the engine guy saying don't go mad with the ev27. Knowing all of the above, he said using a .020 base and a .030 head was just about right?

[kd]

I agree with him.

[1340evo]

With who? The engine guy...

From your calculator, I get

8.51:1 static

And corrected for the cam ev27 gives

7.98:1   ? what ever that means?

If I shave heads to 74cc, I get 9.15 : 1
But would need to take .028 off the heads .. is this right

Or just but new gaskets to give .042 sqish

Or do I just build it with what I have....  .020 base gaskets and .045 heads?

Guess what I need to know is what it does to the drivabuility of the bike?

Whats the most important to get right... Squish or CR?

[John D]

Just for reference, our Darkhorse spec is +.002/-.002 at 2" from centerline of ConnRod, so essentially a 4" bore piston.  We have developed pins and ground surface with indicators to verify every connrod that comes through the door (Including brand new connrods). 

When we replace wristpin bushings they are sized with a TobinArp pin boring machine (1960's version) and then verified on our "rod checker" to make sure big end and small end are parallel within that same +/- .002" spec at 4"

The best way to resolve wristpin / rod alignment issues is before they are installed back into the crankshaft!

[1340evo]

Just for reference, our Darkhorse spec is +.002/-.002 at 2" from centerline of ConnRod, so essentially a 4" bore piston.  We have developed pins and ground surface with indicators to verify every connrod that comes through the door (Including brand new connrods). 

When we replace wristpin bushings they are sized with a TobinArp pin boring machine (1960's version) and then verified on our "rod checker" to make sure big end and small end are parallel within that same +/- .002" spec at 4"

The best way to resolve wristpin / rod alignment issues is before they are installed back into the crankshaft!

so if its +/- .002, does that mean overall it could be .004? (i know I'm 3.5 inch)

[John D]

At a 3.5" piston it should be less using our specs and tolerances

[1340evo]

So

what do I need to work on. I've ordered the new gaskets to get me the squish.. do I leave it or work on CR?

Squish I'll be at .042 so close enough, CR I'm at 8.5 : 1 using the calculator?

[rigidthumper]

Years ago, we would routinely take .050" off of EVO heads, and use thin gaskets to achieve a final quench distance between .030-.036.

[1340evo]

Hi, well I'm at .042 quench and 81cc heads, 8.5 CR... and for problem free motoring, thats how its getting put back together. Built and in this weekend.

Thanks for all the input

[98fxstc]

Hi, well I'm at .042 quench and 81cc heads, 8.5 CR... and for problem free motoring, thats how its getting put back together. Built and in this weekend.

Thanks for all the input

may be problem free motoring, but will be soft at that compression and less than efficient combustion
you have done a lot of work and missed an opportunity
go back and read advice from rigidthumper (both posts)

[1340evo]

Arrrg. so I have my squish at .042.
I can still mill the heads if it makes a big change.

Putting it back as I have it now is better than std though....

What gives a 'nice' improvement? 74cc maybe a bit too much ??

[Hillside Motorcycle]

We set a 27 at 9.8 cr.

[Don D]

Arrrg. so I have my squish at .042.
I can still mill the heads if it makes a big change.

Putting it back as I have it now is better than std though....

What gives a 'nice' improvement? 74cc maybe a bit too much ??

Probably 10ft/lbs and half that on power if you follow the formula that I and others use.

[tdrglide]

Years ago, we would routinely take .050" off of EVO heads, and use thin gaskets to achieve a final quench distance between .030-.036.

That was the standard hop-up among me and many of my friends back in the late eighties and nineties. Along with the EV27 or EV3 cams

[1340evo]

Arrrg. so I have my squish at .042.
I can still mill the heads if it makes a big change.

Putting it back as I have it now is better than std though....

What gives a 'nice' improvement? 74cc maybe a bit too much ??

Probably 10ft/lbs and half that on power if you follow the formula that I and others use.

27 and 9.8?  without milling the jugs .042 is the best I can get.

so I can still change the CR.... don't want problems like starter won't turn it over, need a new carb, blows gaskets etc.. so on a 81cc head, how much to shave off to make it a nice Sunday ride if I don't take the sports bike out.. I'm not looking for anything great, just make it right

If I did mill .050 would I need adjustable rods.. want to keep the std rods

[jsachs1]

Last 3 sets I did with EV 27 cams, 80". I set the chambers at 78 cc., 0 deck, .030" MLS gaskets, stock flat tops. No PMS, happy customers.
John

[1340evo]

Last 3 sets I did with EV 27 cams, 80". I set the chambers at 78 cc., 0 deck, .030" MLS gaskets, stock flat tops. No PMS, happy customers.
John

Hi John, thats interesting. I have .042 squish and I'm kind of stuck with it as no .030 MLS available in the UK right now. (.016 base and .036 head)... but 78cc is less of a shave of the heads.
so if I'm at 81cc now, how much do i need to take off?... and did they run std rods etc  ... 

no PMS?.. whats that?

cheers.

[Ohio HD]

Hi John, thats interesting. I have .042 squish and I'm kind of stuck with it as no .030 MLS available in the UK right now. (.016 base and .036 head)... but 78cc is less of a shave of the heads.
so if I'm at 81cc now, how much do i need to take off?... and did they run std rods etc  ... 

no PMS?.. whats that?

cheers.

Your talked to three shops in this one thread that can send you the head gaskets. I don't understand the difficulty?     

[1340evo]

If anyone is willing to send Gaskets to the UK, I'm all ears 

It would get me another .006 off my squish taking it to .036"

then CC the heads maybe to what John says above or a tad more.

Want to stay with std bits like rods, carb, starter etc...

[kd]

Like Ohio said, there has been many suggestions for you and all along the same line. You are fortunate enough to have a high level of understanding in the conversation and have asked some good questions. Some of these folks make a living building lots of engines and do so with high respect for them and their work. There seems to be a general recipe aimed at what you are looking for. When a chef gives you a recipe you don't substitute salt for sugar or whole wheat flour for pastry flour. I think if you reread your thread you'll figure out where you need to go. You have your engine in a state that it will be easy to do.  It would not make sense to experiment if you can do what is proven to work. 

I also would suggest you talk to the shops and builders that have offered their advice and see what you can get going to move you forward.  Confirm before you buy anything else and source the parts you still need through one of them or from where they suggest. Things like gaskets are available in several thicknesses and any machining should be based on what is available for assembly to get to the sweet spot. Select your target and don't compromise without good alternatives that work.

I sense you may be feeling overwhelmed with all of the weird measurements.  I get that and know the feeling as many of us do or have.  Take a deep breath and talk to the folks that can help you.  They have already stepped up to the plate.  Some times too much information is just that,.... too much information. Your Evo plan is a common one that has existed for years and a safe no PMS (no mood swings due to fuel, temperature etc.) engine recipe has been offered.  Try to get an understanding of the reasons and safe parameters.  Put the pieces together sensibly and not helter-skelter or because it's all that is available down the street.  That's a common problem no matter where you live.  You will have a sweet running Evo you will be happy with for a long time.  I know you want it done right now but that may be an expensive mistake.

[Hossamania]

I don't know for sure, but adjustable pushrods will probably be a good idea, especially if the heads, deck height, and gaskets are changing.

[1340evo]

Thanks KD and everyone for helping out here, not a lot of free advice in the UK and machining / parts cost a lot!

I'm not wanting to do anything with the jugs now they are re-bored and honed for the new pistons, that in turn have been balanced to the crank and rods, just in-case I damage them. (the builder should of done all this! I did ask him to address the cylinders but he refused saying its not a good idea??)

If I get .030 heads, that gives me squish at .035 front and .039 rear. would this cause vibration (could equal out on the base gasket using one at .016 and one at .020 to get both to .039). So not zero deck, but within the .030-.040 as suggested.... or get a .010 base and a .014 base if they exist to get me to .033 so a -.003 deck?)

Then I'll get the heads to 78cc as above.... sounds like a plan??

At this will I need adjustable rods?

[Don D]

Don't trip and fall over .004 difference. Leave it alone and just cut the heads

[1340evo]

Really... I have .016 and .020 base gaskets now.. Just thought it would be best to equal them out... or get .010 and .015 that I've seen?

But thatks for that.. you don't think .004 will impact on anything...

so stick with the .016 bases on both... .030 head and heads to 78cc 


I'm assuming you can mix James bases and Cometic heads... just follow the instructions for the head gaskets.. correct?

[Don D]

If you already have the deck heights close by gaskets, .004, carry on and cut the heads.
I personally cut the barrels, it is simple with the tooling I have. But respect that access to that may not be great in other places.

[kd]

Like Don says, getting it close with gaskets is good to go for your purposes. There should be no problem mixing the manufacturers of gaskets and yes, the head gasket instructions are the ones to follow.  Be hospital operating room clean on the surfaces at the engine and the gaskets.  Oily finger prints can handicap the sealing ability of both.

[rigidthumper]

You asked a question:
And corrected for the cam ev27 gives

7.98:1   ? what ever that means?


Static compression is the ratio of total volume with piston at BDC (AKA V1) vs remaining volume with piston at TDC (AKA V2), so the compression would start as soon as the piston starts upwards.  Corrected compression takes into account the compression doesn't actually start until the intake valve closes, so it only includes piston swept area after intake valve close in the V1 measurement.

I was taught that 10x the corrected compression ratio would be a "ballpark" octane requirement in a carbureted bike- so a corrected CR of 8:1 would need ~80 octane fuel. John's recipe sets the CCR @ ~8.4:1, so would be drama free with any commercially available fuel.

[1340evo]

Thanks Thumper. I understand now

Can you get 0.027 MLS head gaskets for the 89 evo engines?

That would get me to .036 worst case

[1340evo]

Just thinking a bit more on this one, it would be better to trim the barrel bottoms like I asked the shop to do in the first place! Then I can use the gaskets I've bought already.
I can't get the swing on my lathe as its too small, but could take it to work and do it there.
They are finished and honed now so must take care, but if I take .001 cuts I should be able to do it without damage.

guess they don't have to be torqued down to do it... can't see how you could

Thinking is a piece of wood turned in the chuck to the exact ID of the bore that runs just short of the barrel end. then a wooden disc with a ctr in it to push it into the shoulder at the chuck end... and as I say, very small cuts ?

[jsachs1]

Last 3 sets I did with EV 27 cams, 80". I set the chambers at 78 cc., 0 deck, .030" MLS gaskets, stock flat tops. No PMS, happy customers.
John

Hi John, thats interesting. I have .042 squish and I'm kind of stuck with it as no .030 MLS available in the UK right now. (.016 base and .036 head)... but 78cc is less of a shave of the heads.
so if I'm at 81cc now, how much do i need to take off?... and did they run std rods etc  ... 

no PMS?.. whats that?

cheers.

Somewhere in the area of .018" to .020" total removed off each head should reduce chamber volume by 3 cc..
John

[1340evo]

Okay, thanks... will do.

I guess then you need adjustable rods

[rigidthumper]

Depends on the lifters used- most have .200" total travel from top to bottom, and the stock components usually put the lifter plunger depth about .100" down (basically centered in the lifter) when at room temp. This gives enough room for normal operation during expansion when hot, and contraction when freezing. From the factory,  stock, you have ~ zero deck & a .045" (when compressed)  thick head gasket. If you switch to a thin head gasket, say .030", and still a zero deck, the pushrods will now be .015" deeper in the lifter. Not an issue. If you shave the heads, that amount will push the plunger deeper still. Using adjustable pushrods will allow you to set the depth where you wish. Using stock is fine, as long as you know where you will end up, and are comfy with that.

[Don D]

If you don't have the tooling $$$ to properly hold the barrels forget the lathe. I made mine but even the raw materials cost ~700.  Consider modified toe clamps to hold the cylinder on 123 blocks and cut the top. Not centered on the bore axis but better than wood the the spigot bottom as a datum.

[1340evo]

Depends on the lifters used- most have .200" total travel from top to bottom, and the stock components usually put the lifter plunger depth about .100" down (basically centered in the lifter) when at room temp. This gives enough room for normal operation during expansion when hot, and contraction when freezing. From the factory,  stock, you have ~ zero deck & a .045" (when compressed)  thick head gasket. If you switch to a thin head gasket, say .030", and still a zero deck, the pushrods will now be .015" deeper in the lifter. Not an issue. If you shave the heads, that amount will push the plunger deeper still. Using adjustable pushrods will allow you to set the depth where you wish. Using stock is fine, as long as you know where you will end up, and are comfy with that.

Its funny you say zero deck when torqued down. When I'm measuring my deck I'm clamping it down with plastic tubes under the head nut and with a .016 base gasket, would get -.005 & -.009 pistons in the hole... If I torqued it down to spec would you get this moving any do you think? I'm not using the base gasket to measure this, I'm putting the cylinder straight onto case faces anl lightly clamping up so calculating the in-hole dim... I actualy get .007 and .011 proud when measuring.
So under full torque, do the cylinders compress a bit.. and if so, how much?

This is 30 mins in the garage and what I was thinking. It's .060 oversize now so would need putting in the chuck and making true on the machine at work. Push on the barrel and load it with the base ring. if only taking .001 at a time it would work, but I'd need to clock the base before cutting as its obviously coming from trhe bore C/L...  Mad idea??

[kd]

When you reach the torque spec the studs begin to stretch within a  predetermined range that doesn't actually separate the molecules but provides constant tension. The plastic pieces you are using are generally just fine.  The tension on the studs transmits clamping force that is sufficient to accomplish your goals.  The barrels will not compress under the spec torque (but with torque plates will stabilize the shape to the form they run in.

(When the engine heats up under running conditions the barrels will grow taller and the studs will try to follow with the result that there is better sealing of the base gaskets.  For this reason you always bring the engine up to temp before beating on it.  The leaking base gasket syndrome seen with Evo engines can usually be attributed to not letting the engine warm up before getting on it.)

IMO, not using a base gasket when determining deck height. is the way to go.  There is no confusion about whether or not the gasket is compressed enough to give a real world dimension.  Just know that most gasket dimensions are in place and torqued to spec numbers.  Cometic for example says their MLS and steel gaskets will measure to the dimension stated as installed and torqued.

As far as your question about the machining fixture, Listen to HDSP about the process.  A good machine shop should be equipped with the tools to secure the barrels and do a proper clean-up pass or so to get your dimensions.  They will also have the measuring equipment to ensure you get back what you asked for.

[Billy]

If you have a faceplate and a bullnose live center large enough, friction drive the cylinder between the two in your lathe with the spigot in the live center, you don't need to get it very tight to take .001-.002 cuts on the bottom of the cylinder.

[1340evo]

Thanks KD, thats how I understand it, so should be good.

We don't have a face plate, but thats the idea with the wood. Maybe cut down length wise so it located about 1" into the cylinder. I can bore soft jaws to hold it, true the face of the jaws, locate the wood and size it to the bore, then mount the cylinder on the wood and use the MDF shim between the jaws and the top of the cylinder. Then as you say, use a bull nose ctr to make it all tight enough to drive. I could even put a peg between the MDF shim, between the jaws and into a stud hole to give extra drive... that sounds like a plan... 

Obviously the liner is cast iron so need to take care with that so I don't crack it.. only .075 in places... ever put banding or a big pipe clip around it to hold it??

mK2 ready to go. Using the old gasket as protection in place of the MDF as that wasn't that accurate on thickness?... and pegs for drive. Cut down the 3.5" dia bit to about 3" long... 2" in the jaws, 1" out and use as above..

[kd]

Be careful to not cut a sharp inside corner radius up against the liner when you cut the surface.  A sharp corner is a recipe for a cracked liner.  The piston rocks at the bottom when it changes direction.  The side thrust works the spigot and a sharp inside corner is where a crack can appear.

[1340evo]

Yes, noted. infact there is a gap between the liner and the cases so you don't have to go fully to the cast iron, not to mention the large taper on the case bores.

One thing that does worry me is how thin the liner is to put a ctr in there. its only thin in places and the bore is not exactly round as its done between torque plates so you'll get point contact. May be best making a cup locating off the OD and putting the ctr in that.
Will have to see what the face is true to first.. If they don't clock within .001 when set up, I'll not do anything with them and try jig it another way.

Obviously need both to be doable before I do any so will check both before I put the tool in

[1340evo]

Job done. No wood, no soft jaws, no tail stock, just bung it in with some card on the bore and it will be fine 

And it was.. so now have them .004 different in length to match the rods  and the additional few tho off to get the right squish.

Heads next, but they are easy to do

[1340evo]

okay, so re-checked tonight and with my .016 bases and .036 heads, I'll end up at 0.035 squish on both .. looking back sqish is quoted at .030-.036 so in the top end of that... (I could still get .030 heads and then have .029 squish... but no, lets stay as we are)

So next the cc... is 78cc a good place?

[1340evo]

Heads skimmed, so should be both at 78cc now... .023" off one and .027" from the other... may as well be spot on whilst we are at it

Now to take them all in bits again and de-burr, clean 

[kd]

 

[1340evo]

Cleaned off today and CC'd them, both spot on 78cc    now in plastic bags read to fit