Help me determine my piston-to-head clearance!

[wed3k]

its not that they took .035 off the deck surface, the compression height and rod length can be slightly off. everything he is using is aftermarket.

so don't jump to conclusions because it happens all the time.

run k20 pistons? seriously?

[Jarrett]

Well why not? They're 86mm and have a 30mm compression height that would help drop him back in the hole a little bit. Instead of saying something as informative as you did maybe you could shed some light on the issue. The wrist pin can be converted from a press-fit to floating easily enough.

[wed3k]

because they aint forged pistons...obviously.

[GhostAccord]

What aren't forged? You saying that there are no forged K20 low compression pistons available?

I think the 30mm compression height is a good idea. And to be honest, I have never seen a quality piston & rod combo be .035" out of spec... They come with a spec sheet, if they are off from that send'em back!

I would sell the 30.55 CH pistons you have and buy a set of Forged k20 Wiseco's or a custom set of 30 - 29mm CH ones. The thicker head gasket fix works..... if you trust having your head gasket act as a cylinder wall.

What are the specs on the top ring land thickness? What is your piston to wall clearance? You realize that piston is going to rock a little bit in the cylinder as well.

[Jarrett]

He's not using factory cast F22A pistons. Why would I expect him to use factory cast K20A pistons?

[wed3k]

why would you run a forged piston not designed for the motor?

if you look closely, it looks as if the top of the piston is stepped. hes measuring at the highest part.

[GhostAccord]

I wouldn't. However an off the shelf set of forged K20 pistons might be a bit cheaper than a set of custom pistons. That is if cheap is what you're going for. I paid $500 for my custom Wiseco's with an 89mm bore and a 29mm compression height. IMO that's fairly cheap for pistons custom made for my engine.

Those are dished pistons and he is measuring from what looks to be the top of the top ring land. That is where I take my measurements from.

[Jarrett]

I'm not suggesting an ideal scenario. An ideal scenario for me would be to have the machine shop redo the work on a new block because .035" is a large error on their part. If I'm building for boost I don't want the integrity of my engine to rely on a super thick headgasket. They would redo it and I would reinstall all of the F22A parts I originally bought for the build.

[GhostAccord]

^x2

[ON_N20]

I'm not suggesting an ideal scenario. An ideal scenario for me would be to have the machine shop redo the work on a new block because .035" is a large error on their part. If I'm building for boost I don't want the integrity of my engine to rely on a super thick headgasket. They would redo it and I would reinstall all of the F22A parts I originally bought for the build.

Thanks for all the responses guys . I had a long talk with the machine shop to figure things out. According to them they only mill off as little as possible and the guy that did my machine work says he did not take off alot - unfortunatly they did not record exactly how much . What they did record was the counterbore they bored to allow for the wider flange at the top of the sleeve. The flange on the sleeve is .375" deep, and they counterbored to .370" which would have left the sleeve extending the block by .005" before they milled the top flat. The stock darton sleeve length is 5.500". I removed a piston, used a digital vernier caliper and measured my new sleeve length: 5.492".

So my sleeves after machining are .008" shorter now than before. Keep in mind because of the way they install the sleeves, .005" would have extended the block before they machined - and been machined off. So I calculate, taking into account how far the sleeve originally extended, the machine shop took off a total of .003" during machining the deck surface.

I'm fairly confident my measurements are correct, I measured 3 times and zeroed out the caliper each time, and was accurate to .001" each time I measured the length. So from what I calculate, it was not the machine shops fault. Its possible maybe the block I bought could have been previously machined, and now with the second machining, is too short, I dont know for sure. They did have the piston tech sheet, and probably should have measured and then caught this, but then again the block I got was used and with an unknown history.

Theres not really any reason to find someone to blame at this point, I just need a fix now.
I really wish I could just find a company that can fab a MLS headgasket in the correct thickness, that would be easiest. Even cometic cant, they could only make me a copper one. As for the post about the K20 pistons, obviously yes they would need to be an aftermarket forged, and for that money I might as well just start blank and order a set of pistons to my specs. Im nearing the end of my budget so I would prefer a cheaper (and hopefully still reliable) alternative at this time.

Also, a slightly shorter connecting rod would fix this too, but I dont know of any options as far as this goes.

[Jarrett]

If you don't know the history of the block then I retract my previous sentiment toward your machine shop. I still wish they would have been a bit more thorough with their measurements and recordings. Oh well.

I still maintain that aftermarket could be a viable solution. A set of forged Supertechs is $390. But if you've got the extra $110 laying around then custom pistons would be better. GhostAccord would be the better judge of the downtime you'd be working with.

[ON_N20]

If you don't know the history of the block then I retract my previous sentiment toward your machine shop. I still wish they would have been a bit more thorough with their measurements and recordings. Oh well.

I still maintain that aftermarket could be a viable solution. A set of forged Supertechs is $390. But if you've got the extra $110 laying around then custom pistons would be better. GhostAccord would be the better judge of the downtime you'd be working with.

I couldnt have said it better myself. I mean yeah I could be to blame for not measuring the block, but I dont have the means to do so with a close tolerance, and as well the machine shop doesnt normally have such a problem like this, so I guess it is what it is.

Wow $390 for a set of Supertech pistons doesnt sound half bad at all, I paid about $550 for my Arias pistons I have now. Im not familier with the ones your talking about though regarding fitment and compression ration, or what there for exactly, etc., but that sounds like a good deal regardless.

But yeah any pointers at this point would help me out alot, its a shame to be 99% there and ready to go, and just watch my build (and my car) just sitting still. I didnt think this would turn out to be such a big deal lol. I really appreciate the help guys

[wed3k]

machine the the top of the piston and send them out to have thermall coated.

im surprised cometic can't make a mls headgasket? i spoke to someone there and they told me to send the headgasket. i sent it but apparently they never recieved it and my project just stopped there.

im putting h22 pistons in my f22 block and my pistons are sticking out about .040 (Calculated value) and im just going to put a thicker headgasket and call it a day.

[GhostAccord]

See what you can get for your Arias pistons and call around to see what a set of 29-30mm compression height F22 pistons would set ya back. John & Rob down at Race Engineering Inc set me up with exactly what I was looking for. Competitive prices as well.

Just remember to cc your piston dish if you do machine .035" off the tops of your pistons. the compression may be up in the high 9-10: range.

[ON_N20]

machine the the top of the piston and send them out to have thermall coated.

im surprised cometic can't make a mls headgasket? i spoke to someone there and they told me to send the headgasket. i sent it but apparently they never recieved it and my project just stopped there.

im putting h22 pistons in my f22 block and my pistons are sticking out about .040 (Calculated value) and im just going to put a thicker headgasket and call it a day.

Yeah I think machining the pistons is my plan of action at this point, my machinest referred me to another local machinest capable of doing them right, he has done many already like this. He will also need to deepen the valve reliefs too. Essentially when he's done, the overall compression ratio and quench area outta be about the same as it was the first time my engine was built with these internals (cracked a sleeve on my original F22A1 @ 86mm, was running about 16lbs boost for about a year).

Yep Cometic says they cant make me a custom gasket for the F22. Apparantly they dont have the template or "tooling" in stock to be able to modify or produce the MLS headgasket, but they could fab a solid copper for $98- not bad, but for the copper. Cometic can however customize just about any bore and thickness for almost any other Honda engine, the H22, J30 v6, B, D, even the F20 S2000 engines etc., but go figure they dont support the F22's yet. They may support them soon though, when I called about my gasket, another guy called right before me about a F22 custom gasket. Hurry up Cometic

So your putting H22 pistons in your F22 and your planning on a thicker headgasket to make it work? Your in the same boat as me, finding a thicker headgasket is going to be hard, although if you do find one, PLEASE be sure to post and let me know! If anything you may have to do what im doing and modify the pistons, if you cant find a thick enough head gasket. If I go and get my pistons shaved, all take some pics and make sure to keep this thread going, so we at least have a decent viable solution for everyone else reading this.