Possible damper on the engine rebuild

[Legacy777]

Well I got a call from the machine shop, and they said two of the cylinders have about a 2 thousandths taper out of the normal spec.

A 25 thousandths oversized piston would more then likely work after boring and honing, and take of things. However there's none in the country, and it could take two weeks, four weeks, or possibly longer for pistons.

Is this taper issue something that can be lived with or is it something I should just bite the bullet and have them take care of.

Also....is there any other piston manufacture that you guys would recommend I call to see if they have any oversized pistons & rings in stock?

I've called several subaru dealerships and crawford performance.

[Legacy777]

One thing I was curious about is that the FSM states to take measurements at 68 deg F. The shop I took the block to doesn't have AC, and it is NOT 68 deg F down here. More like 90-100 deg F.

I spoke with crawford about the temp thing, and they said in terms of bore size, it may make a difference, however in out of roundness or taper, it probably won't make that much of a difference.

Crawford also mentioned something about not changing pistons, but mainly not changing rings if everything's working. There reason was that because it's used, putting new rings or whatever in, introduces more issues. Whether I believe that, or if it's an over-cautious engine builder....I'm not sure.

I'm leaning towards having them lightly hone the block and putting std size shit back in.

[douglas vincent]

I would go with the light hone and put the regular stuff back in. Considering how much abuse my block has had and never had a honing, it is running wonderfully.

[Legacy777]

yeah...I tend to agree.

Other comments?

[Matt Monson]

TWE and AxisPowerRacing are two other speed shops that do a fair number of builds on the Ej22's with overbores.

Crawford's comments about reusing the rings make really good sense, as long as you marked the rotation and gaps prior to removal so that you can reorient them to the exact same placement. If not, reusing the rings could double the issue at hand and you could have a real oil burner on your hands.

Are you rebuilding it to stock specs? Or are you changing heads and going for silly boost and power levels?


If it were my engine, I would bite the bullet and overbore it and put brand new slugs and rings in there...

[Legacy777]

Matt,

I'm a little confused about your comment. You seem to be contradicting yourself. Maybe it's a typo. Any clarification would be appreciated. Also, why would putting new rings or reusing the old rings double the issues?

Crawford's comments about reusing the rings make really good sense, as long as you marked the rotation and gaps prior to removal so that you can reorient them to the exact same placement. If not, reusing the rings could double the issue at hand and you could have a real oil burner on your hands.

I'm rebuilding to stock specs. I'd be happy with about 300-350 hp out of it.

The lead time is what my main concern is with getting overbored stuff. Costs would be pretty much the same, and probably cheaper since I'm getting pretty good pricing on subaru stuff.

[Matt Monson]

Let me try and clarify. So your bore is out of round. Your old rings would have worn in a pattern similar to that. IF you put them back with the exact same orientation, then the bore is going to match up to the wear pattern.

But if you put them back in rotated, say 30 degrees, off of where they were, then you are going to have a big gap and a big drag because of the ovalization. You can push a circle through a circle in any orientation you want. You can only push an oval through an oval cleanly in one orientation.

So, if you haven't marked the rings for placement, then my logic says you will have less oil leakage with new round rings in your oval bore than trying to reuse the old ones...

EDIT: Wait a minute. Stop the presses. I just re-read and saw that I misunderstood your problem. Your bore tapers from wear and is not out of round. Given that, if you don't want to wait for new pistons, have it honed to as close as spec as possible, and take your chances. Basically, what that taper means is your bores are worn out...

[Legacy777]

Yeah, they said nothing about out-of-round, just taper

So basically taper means that the bore is a little wider at the top, bottom, or somewhere in between....correct?

[0perose]

Yeah, they said nothing about out-of-round, just taper

So basically taper means that the bore is a little wider at the top, bottom, or somewhere in between....correct?

yes

[Legacy777]

Yeah, they said nothing about out-of-round, just taper

So basically taper means that the bore is a little wider at the top, bottom, or somewhere in between....correct?

yes

thanks

[professor]

don't panic - 0.002 taper is nothing, almost. In fact it is within the tolerance that is considered acceptable for re-honing and putting in fresh rings (of stock size), and the same pistons. If there is 0.002 taper then the ring gaps will open about 0.006 when encountering the max taper, which is no big deal at all.

That's what I would do.

You might burn a little oil on break-in (use conventional first couple changes) till the new rings seat, but it'll come together fine.

What Matt was saying is still largely valid, if you were going to put the same rings back in (almost always foolish unless made of unobtanium), they will seat much better in the exact same position, but its pretty damn hard to ensure that.

Boring over and using oversized pistons would be the absolute best thing to do, but not really necessary at that level of wear, provided there aren't big cylinder wall scores or other issues.

[Legacy777]

I'll need to check, but I'm pretty sure what the guy meant was that it was 0.002 over the taper limit.

The FSM has the standard taper at around 0.0006, and a limit of 0.002. So I think the machine shop said I'm 0.002 over the limit, which would give me a total taper of 0.004

[Legacy777]

I'm just going to get them lightly honed/cleaned up, and let 'er rip.

After talking with Rick at CCR, he said machine shops measure taper to the bottom of the cylinder, (which this machine shop did) and piston rings aren't hitting down there.

Plus Rick said, if you overbore, the engines tend to run hot.

[Matt Monson]

Trust Rick. I think those guys know more about these engines than any of the speed tuners. (*sidenote: I want to thank CCR for taking my turbo chassis off my hands *end sidenote*).

Find out if it is off at the top or the bottom. A lot of the wear will be at the top. You probably can feel a lip at the top where it has worn more...

Professor:
Thanks for acknowledging my other points. That's why I left them instead of editing them out. I figured someone may read this later with cylinders out of round (far more likely on an open deck build)...

[Legacy777]

The thing was.....I did not feel any kind of lip in the cylinders.....oh well....no biggy.

[Legacy777]

Picked up the block from the machine shop today.

The bore turned out to be 3.8171 @ 80-95 deg F. I had B sized pistons in there before. They list the bore dia should be 3.8148-3.8151 @ 68 deg F.

I'm going to stick A sized pistons in there, which are supposed to fit in 3.8151-3.8155 @ 68 deg F. The clearence is a little off, but should be ok. I don't know if temp would have that much to change things, but I'm going to check the tolerences on the std B pistons I have with the block when I get home to see what I get.

[BAC5.2]

Why would increasing bore cause the engine to run hot?

STi motors don't run hot, and they have a larger bore than the EJ20 with the block being the same physical size. EJ25's don't run any hotter or colder than EJ22's, do they?

Why?

[Legacy777]

Why would increasing bore cause the engine to run hot?

STi motors don't run hot, and they have a larger bore than the EJ20 with the block being the same physical size. EJ25's don't run any hotter or colder than EJ22's, do they?

Why?

I would assume they don't use the same size cylinder liners for all three engines. When you bore the liner and put oversize pistons in, you're decreasing the liner thickness. Less mass to help dissapate heat, etc.

That's only a guess. Rick didn't get into details as to why. He was just telling me what he has experienced.

[Legacy777]

I checked clearences on the pistons. They are a little higher then what they should be using the old pistons. However piston ring gap is within tolerences, however just a tad bigger then standard.

Pics
http://www.main.experiencetherave.com:8 ... /ej22t/06/