im doing a super cheap rebuild, -bearings rings and hone....
on my 355.

i know this isnt reccommended, but im using stock crank, rods, and dished cast aluminum pistons...i cant afford anything better as work has slowed more then 50%.
but anyways, i took the engine aprt after running 7-10 psi last year and had two spun rod bearings, but the pistons looked totally fine.... no signs of detonation or anything.
i have a wideband o2, so i plan on keeping a close eye on the air/fuel and feeding it plenty of good octane, but id like to run 10-14psi this time.
355ci
AFR 195ccs
Steel head gaskets
small turbo cam
CSU blow thru
Turbonetics TC-78

if i do a quick 3-stone hone, what should i file my ring gap to?
like to try and run 14psi, and make as close to 650 crank hp as possible, i know this is a ticking time bomb but i dont have other options.


thanks for any advice,
Keith

 

I'd go at least 0.024" on the top ring. Maybe even 0.028"

 

thanks, i did try to search for some quick info on this before posting... most of what i found was just manufacturer recommendations and i was looking for a little more decisive answer relating more to my exact boost level and application.

thats pretty close to what i was reading tho, .026-.028" on the top ring and .024 or so on the second ring.

 

I'm still skeptical of cast pistons with 10 psi, but, as I'm sure you know, tho some readers might not, if the gaps are too tight and the heat makes the ring ends butt, there go the tops of the pistons, guaranteed fail.

 

I consider this my gospel;
http://kb-silvolite.com/article.php?action=read&A_id=56
(wider is better)

 

With cast pistons YOU are not going to have fun long!

 

But, if you don't have the money and don't mind rebuilding again soon, then go for it. I use .025" gaps and run 10psi. .028" or larger sounds good for 14psi.

 

Depends on his tune. If he has a WBO2 and knows how to use it then he won't have any problems.

 

I agree that it may work fine, and I hope it does! Good Luck!

 

thank you guys, i am gonna try to get the motor wrapped up sometime next week. i think im gonna try .028"/.024" (top/bottom) and hope it doesnt have too much blow by, and hope it holds together for at leas a couple good passes.
i'll post results when i get em.
thanks again, Keith

 

Keith,
I have a complete blower rotating assembley at a really good price. All forged. Just to let you know.

 

I would just use the manufacturers recommendations, on the high side, for whatever rings you buy. They've spent alot of time and effort to write up those specifications for a reason.

every ring I've ever seen has had that documentation to go along with them.

that said, going to a larger gap will not adversely affect the engine performance, relative to the reliability you gain. too large a gap will eventually start to drop power through pressure loss, but you'd have to leave 'em really wide. I dunno if that was clear or not, what I'm trying to say is between a tight gap for 'power' vs losing a couple HP for a large gap, the large gap is preferred.