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Old 03-18-2000, 02:36 PM
mopardude mopardude is offline
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Location: niagara falls ont. canada
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I am building my 451 strip street motor it will be about 11.0- 1 comp. ratio what is the tightest end gap i could use? I usually put them at 0.019 top & 0.017 sec. do u think i could go 0.017 top & 0.015 sec.??
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Old 03-19-2000, 03:35 AM
Challenger Challenger is offline
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Location: Mark Twains hometown- MO
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Mopardude

What does the piston manufacturer recommend. As a starting point, a gap of .004 times bore size for the top ring and .003 times bore size for the second ring. This kinda works out to .017 on the top and .013 on the second for a big block. Increase the gap 25% if using nitrous. I just got done file fitting Ross 12.5 pistons in a 440 bored .055 at .018 and .014. Err on the loose side when fitting the rings.
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Old 03-19-2000, 05:59 PM
vsteel vsteel is offline
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Just to throw out a new theory into the mix.
I have read where good results have been had by putting a large gap in the second ring .022 The idea behing this is by letting pressure out of the gap between the top and second ring will let the top ring seal better because of the higher pressure differental.

I have never tried this, the last motor that I built I hand filed the rings to the .004 and the .003 rule of thumb. blow by seemed nil. I raced this combo for two years and never had a problem. The thing you want to stay away from is getting the gap too tight. If this happens the ends of the rings will butt together. This could cause scoring in the cylinder wall, breakage of the ring, or removeal of the coating of the ring (if moly or chrome plated.)
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