FrontEngineDragsters.Org Forum
Technical => Matt Shaff's Engine Shop => Topic started by: wideopen231 on May 23, 2015, 05:36:44 PM
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Wondering what piston to wall most are running with NA motor. I know my blown alky stuff was .010 to .012. Was thinking NA motor is suppose to be little tighter. Going to have to run what I have for while anyway.Just wondering how much extra clearance I may have.
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Typically the piston is built with the clearance the manufacturer recommends, a 4.310 bore piston may come in at 4.303 which means they want .007 clearance
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He is right--it is built in for normal applications--modern allys do not expand like the old TRW slugs from back in the day. I usually add around .001 and have never had any issues--I am not afraid to have much more as in the case of well used--rehoned several times-- in a drag race engine. Street I keep it as close as possible --
Any sloppy way too big will run and can win but for ring seal-- and to keep piston rock down --the mfg's numbers are the way to go--today everyone runs a stroker with a "hockey puck" piston so controlling piston rock is very important for ring seal
I love a loose race engine--despite what all the experts say about oil pressure-oil control, ring seal etc they always run Great! A sweet-perfect valve job on a sloppy loose engine makes the best combo for me every time
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These pistons where built for blown alky not NA. May be same clearances ,would just seem blower deal would need little extra. I know that pistons are sized for cylinder 4.250 and these are 4.2385 for most of them giving me .0115.My 4.310 stuff set about the same . I was wondering if they would be tighter with NA. These are also old tech since they are 1995 stuff.Oh yea they are on heavy side compared to today designs. Rings pakage is .043 dyke,1/16 and 3/16 ,wondering about piston rock & seal with extra clearance if it is extra.