What ring gap is everyone running? I'm curious cause I rebuilt my engine about 6 months ago and now its starting to blow smoke. The machinist I had balance the engine said with KB silv-o-lite pistons the gap on bottom should be .26 and the gap on top should be atleast .28 otherwise I would blow off the top ring. He said it would smoke a little on startup. Which it did, but now it does it all the time. Does this sound right? I know I should have asked a long time ago

 

The end gap factor for a street NA app. is .0065". I set my top rings to about .030", and the second ring at about .020", my engine is a 355 however, so you will probably need more gap with a 383. Your machinist is right about the top ring, if the gap isnt wide enough, the ring heats up, the ends butt together and rip the top of the piston off.

 

Ok cool, I was just checking. I plan on getting new heads in the near future and want to rebuild the engine again.

 

don't remember the factor but my 402+.030 came out to .028 top ring gap, if i recall the second ring was stock gap.

 

My second ring gap was normal as well, the top ring gap is the only one to be concerned about.

 

Does anyone know the formula or know where to find it?

 

http://www.kb-silvolite.com/clearance_pop.php

 

damn hell ya dude thanks!

 

.032 on my top rings.

 

No prob.

 

I once had KB pistons and had bad oil control problems...that was through my first engine builder...I found a new builder and told him I had oil control problems,wanted my engine fixed again...first thing out of his mouth,before I told him,he asked"are you running KB pistons?"

I said Yeah! why?? and he said come here and showed me a box full of hundreds of old KB pistons he saved from other engine rebuilds he fixed.They all had oil control problems and were prone to cracking on top.Just about everyone one of them had cracks I could see.So he guessed before he looked at the engine,I probably had a problem with them pistons...On tear down I DID!!!

My jaw dropped...He told me he would never use those pistons in any engine he rebuilds.He fixed my engine with new pistons and etc and I never smoked again.Funny,I wasnt the only one coming in for a rebuild gone bad with those pistons,I was one of many.
Just thought Id share that.

 

So what you are saying is that they are junk? Guess you get what you pay for. Anyone have recommendations for pistons under $400?

 

Lots of people (me included) have had good luck with TRW Forged.

 

I run KB slugs with no issue at all.

As long as you have a machine shop that is capable of setting up a bore properly you will have no problems either.

Just gotta pay attention to detail.

 

Agreed. Its not the pistons fault if the engine wasnt assembled properly, the vast majority of cases are likely user error.