Piston ring gap help (PLEASE!)

[Gary_gtx67]

Ok everyone I finally broke down and after finding out my motor was pulling very weak compression and speratic numbers I pulled the motor. Only to find severly glazed cylinder walls and rings gaps at .031. My bore is a 4.275 and and I have the .030 over keith black hyper tech pistons. I am being told that the math to find the correct gap is .004 x bore = gap. Is this true? I also found this http://www.kb-silvolite.com/article.php?action=read&A_id=32

which led to this.http://www.kb-silvolite.com/calc.php?action=ring

It is just a street application.:eusa_eh:

 

[383man]

On the hyper tech pistons you have to run a wider top ring gap because of the exspansion of them pistons. Look up the ring gap for the hyper tech pistons on their site if you dont have the instuctions with the pistons or give them a call. I forgot the gap but its something like .025 or .028 on the top ring and the second ring is a normal gap like about .018. But look it up because I am not positive on the top gap. Ron

 

[Gary_gtx67]

ok Ill ask. The second ring is also .031 as well. Could just a few thou really have caused all my issues?

 

[daredevil]

Probably not unless the gaps were lined up. 31 would be a good gap for nitrous on hypereutectics so it should work because you dont spray 100 % of the time. Ring gap is mainly to prevent rings from butting.

 

[Gary_gtx67]

Just spoke with John at Jegs racing and after measuring and talking with him it seems that I was not instructed properly on how to break in the the motor on sealing these rings and pistons. Also his information shows to gap the rings at 20 thousands both of them.

 

[Meep-Meep]

383man is pretty much correct. You will end up with a larger than normal top gap and your example of .004 as the multiplier is too tight. I'm running those pistons in my 440 and my top ring gap was nearly .030". The multiplier I used if I recall correctly was .0065.

Hindsight being 20/20, the best you could have done to see where your compression was going was to do a leak down check.

 

[fugly]

Do NOT rUn that top ring at.020...that is too tight....can't tell you how many times I have seen people dest Roy an engin and blame it on the pistons.....the proper multiplier for the street is.0065 so you need .028 top gap....

 

[yannick47]

got them same pistons on my 440 and i run .028 on first ring and .018 on the second ...

 

[lewtot184]

Do NOT rUn that top ring at.020...that is too tight....can't tell you how many times I have seen people dest Roy an engin and blame it on the pistons.....the proper multiplier for the street is.0065 so you need .028 top gap....

this is correct! do not run .020!

 

[RustyRatRod]

Just spoke with John at Jegs racing and after measuring and talking with him it seems that I was not instructed properly on how to break in the the motor on sealing these rings and pistons. Also his information shows to gap the rings at 20 thousands both of them.

Then "John" is a stupid dumbass that has absolutely no place giving engine building advice. Here is the formula for YOUR engine.

YOUR bore 4.275 x Keith Black's formula given of .0065" equals .0277875, or .028". This is strictly for street. If you are going to do any racing, then replace the given with .0075. If you're doing other things, there are different factors for that as well. Here is the chart.

Sorry. The pic turned out too small. Here is the link. Scroll down to page 54. http://www.kb-silvolite.com/assets/automotive_catalog.pdf

I'll add this, too. When it comes to top ring gaps on hyper pistons, I am pretty liberal. I would go .030 on your top rings and never look back.

 

[dvw]

As Damon stated .020" is too tight. .031" will hurt nothing. How did you decide you have a "Glazed" wall? A smooth ROUND bore with .031" gap would not cause your problem. Lining the gaps is not a huge issue either. How do you know you don't have a guide/valve problem? Pour solvent in the ports and see if they leak. There should be virtually no break-in with Moly rings. How were the bores honed before assembly? What break in did you use that was incorrect? Read this. http://www.kb-silvolite.com/article.php?action=read&A_id=56 . Read this as well.
http://www.kb-silvolite.com/article.php?action=read&A_id=56.
Doug

 

[Gary_gtx67]

I did do a leak down and that's what made me pull the motor. I was having a do he from %35-%45 leak down past the rings. Both rings are set at .031. With not having many miles would it be ok to just reuse these rings??? I went ahead and deglaze the cylinders with honing stones and drill. (With lube) I got the swirl marks back and all the gloss is gone.

The break in that John was stating was to break in under a load 0-30 with 75% pedal using the transmission to keep a load on the engine to slow down I stead of the brakes Doing this for about 20 mins. Ever heard of that?

 

[RustyRatRod]

Oh God. Now we're gonna argue about break in? Are you serious? Bust it off, break in the cam, get the tune right and drive it. It'll break in just fine. Them rings know when to seat and there's virtually nothing you can do that'll influence it short of honing with a torque plate.

Oh and the lining up the ring gaps thing is a complete myth. Since rings rotate on the pistons as the engine runs, they line themselves up a good bit over time. It's all hooha I tell you.

 

[Gary_gtx67]

:angry9:Nobody is arguing about break in.....

- - - Updated - - -

:angry9:Nobody is arguing about break in.....

 

[RustyRatRod]

I think you need to throw John under the bus is what I think. I'm drivin, you hold him down.

 

[Gary_gtx67]

Lmao!!

So should I just reuse my old rings and just rehone?

 

[RustyRatRod]

Cheap as rings are, I'll be damned if I wouldn't replace them and file the new ones to fit. You're not lookin to do it twice, right?

 

[Gary_gtx67]

Agree. What brand does everyone like or rather prefer?

 

[RustyRatRod]

I have JE for my 383. Mainly because they were the best deal for low tension rings. Most any major brand is good as long as you stick with a moly ring.

 

[Gary_gtx67]

So a set of seal power moly rings will do just fine then