"Uneven" Pistons in Bore

[FishyAbody]

I installed new TRW forged pistons in a 318 with 8k miles on it. After installing all 8 pistons, I noticed that numbers 2,4 & 8 were not perfectly centered in their respective bores. I was able to center #8 by realigning the location of the compression ring gaps to 180°, but the #s 2 & 4 remain "tilted". They look as if they are touching the cylinder walls, but I measured the gaps at .003 (#2) and .004 (#4)(the gap on the "open" end is .014). There was no measurable gap on the compression rings.

Is this a problem? What is the remedy?

The 318 was rebuilt 8k miles ago and ran fine with stock pistons. The vehicle with the engine was wrecked so I pulled the engine and decided to raise the compression by installing the TRW's (the engine has 360 heads). During the teardown, I did not take notice how the pistons sat in the bores.

[Fly Boy]

The pistons will move around in the block a little bit due to the required piston wall clearences. If the pistons are tilted front to back a lot you might want to check your rods to make sure they art not bent. And most important, Check with your piston ring company to see what the gap should be between the ring ends in the cylinder. 14-16 Thousands sounds about right, But if they are too tight, When they heat up and expand you will blow the top off the pistons. Make sure you check the top and second rings. And check with TRW see what cylinder bore clearance is required for the forged pistons. Most forged pistons require more clearance than a cast because thet will expand more when they heat up.

[bubby440]

your pistons will do this because of the load of the rings being compressed. if your ring gaps on top & 2nd are 180deg. apart this should't show as much.

[This message has been edited by bubby440 (edited January 27, 2001).]

[cdignition]

the best way to remedy this problem, is to bolt the heads on. That way you cant see the gap.

[This message has been edited by cdignition (edited January 28, 2001).]

[MOPARMANJAMES]

You said that you measured .003" on the close side and .014" on the far side. My question is what is your piston to wall clearance, period, without any tilt? You should only have about .008" max with those
forged slugs. If your clearances are out of tolerance you can run it like that but it'll be noisy till it warms up, and you'll have reduced life on the rings. Check the wear on the bore with a bore guage, if it's OK then there may be a problem with that set of pistons. Either the bore is too big or the piston is too small by the way you describe the problem. Oh, by the way, that was a pretty funny comment by cdignition, I usually prefer not ever starting the engine so I never have problems!

[This message has been edited by MOPARMANJAMES (edited January 27, 2001).]