acceptable leek down

acceptable leak down

We cant seem to do any better that 10-15% on new build. Molly rings or gapless makes no diff. Pistons are installed dry with ring gaps as per manufactures spec. App is blown alcohol sbc. Thanks,Bob.

 

Leakdown

Has the engine been run yet? I'm not 100% sure but I think you need a little seating time before you can expect really good sealing.

I could be wrong, I don't recall ever leaking a non fired engine before.

Corey

 

That is after 25-30 passes.

 

Leakage

If your numbers are always 10-15% on various ring types, could your heads be the issue? Bit of a long shot but I figured I'd ask anyways. Or are you positive its coming by the rings?

Corey

 

Round bores? ported pistons? Leaking valves? Head gasket seeping?

 

leak it with the oil drained good with the drain plug out listen in there and see if you hear it going past the rings. Ora once told me not to worry about leak down till a motor falls off..and beleave me Ora has more smarts in his thumb than I have in my whole body the man is a BRAIN..Ora tunes dennis taylors car..Dave

 

a chevy what kind of valves can you hear air coming out the exhaust are the intake i had a chevy motor do that it was seeping past the valves i called the engine guy he said dont worry about it with the compression and the blower it would seal up when the motor is hot if you have a stainless steel valve they may be tweakin the end of the valve if its getting real hot on the run mine run for several years doing that and it was fast hell if my engine guy could make 7 of them run on a tractor i figured he new what he was talking about ( bbc )

 

You can here it from the puke tank vent. Traveling through the burn doun tubes to the tank and out the vent. Been the same for 11 years running the car. Two stock blocks and last 3 years with motown block. Our machinest is extremly particular about his work will 30 plus years doing race motors so i have to think the bores are round. No gas ports on the existing pistons. Do most guys shove the pistons in dry? What are you guys getting for leakdown on a fresh motor? Thanks,Bob.

 

Leakdown???

I wouldn't even concern myself with leakdown until the motor falls off. You can't check leakdown on a motor that the rings haven't bedded in yet. Make a few passes before you do. I also wouldn't use moly rings in a blown alcohol motor. I don't know if its a combination of the blower and alcohol or what, but the moly will flake off the top ring. Use the hellfire top rings, a ductile iron second ring or napier ring and a 3 piece oil ring, preferably the Hastings type oil ring, you can't go wrong with those. Forget about that gapless crap. If gapless rings are so good, then why don't the OEM's or NASCAR use them?
What Dave said about Ora is absolutely right. Ora told me the same thing, among many other things.