[taff2]

I've posted this here as well , in case some of you don't frequent the boost section.
I've been advised that I MAY need to run a bigger ring gap than I intended on my turbo combo so I'd like some info or advice from pro engine builders,or what others with similar turbo/blown combos are using.
My combo is a 4.090" bore,3/4 filled,reverse cooled iron block,forged pistons with .006" clearance, C16 type fuel,boost will be 25psi,projected HP around 1200.
I've always followed the ring manufacturers advice on this,in this case for a blown,gas engine, .0055" x bore size of 4.090" = .0224", I then added an extra .002" because the block is filled, I rounded this off to .025". The manufacturers recommendations for a big hit nitrous engine is .008" x bore,which would make it .03272" ring gap,plus the extra .002" for a filled block gives me .035" rounded off,and this is what I've been advised to use. Any advise appreciated,Taff.

[PONTIAC DUDE]

I run .032 to .035. Even on motor never had blowby issues. Second ring at .024

[Steve Barcak]

Yeah, it is wiser to run a wider gap than a tighter one. Later, you can experiment by closing the gaps if you wish.
Only running .006" piston to wall? That is tight IMO. What does the manufacturer say to do? I would be worried about the skirts that tight. Run over double that number on my nitro motor. Normally run .010"-.012" on a blown gas marine set up. I've run .005" on N/A street motors with forged pistons. many think that is way too much but, the 455 lived for 181,000 miles and did not overheat.

[Travis Q]

You don't have to run as much gap on a turbo motor as a nitrous motor. Not as much heat into the top ring. Also, I like a little more gap on the second ring, but that's just me. If it were mine, I would put the top ring at 0.026", second at 0.028". Keeps pressure from building between the rings. Some engine builders don't use this strategy, but its worked well for me.

TQ

[bad69bird]

Originally Posted by Travis Q

Also, I like a little more gap on the second ring, but that's just me. If it were mine, I would put the top ring at 0.026", second at 0.028". Keeps pressure from building between the rings. Some engine builders don't use this strategy, but its worked well for me.

TQ

I concur with Travis. I run mine .030 and .032.

[Torment]

.028 top, .022 2nd on my blown roots, E85, 4.31" bore. As above nitrous motors spec more gap.

[taff2]

Thanks guys. I know some ring manufacturers,but not all of them, are now recommending a bigger second ring gap,but I'm not sure on that ,I've always done it the old way and never had a problem(that I knew of). Even though I think the smaller ring gaps would be more efficient I might err on the side of caution and go for a slightly bigger top gap,just in case the engine gets really hot some time.
Steve, I normally run .004"-.0045" piston to bore clearance but BRC recommended to add .002" extra. I have previously run TRW forged pistons at .0085" without a problem, my machinist took some convincing to bore for these clearances though,he said 'the piston will be like a dick in a shirt sleeve'.

[cgeise]

Was he talking your dick ??????

[taff2]

No,my shirt sleeve.

[bad69bird]

Originally Posted by taff2

...my machinist took some convincing to bore for these clearances though,he said 'the piston will be like a dick in a shirt sleeve'.

LMFAOROTF!!!!

[440GP69]

LOL come on Thats not that loose for a Real 25lb boost race engine!