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I run in a class with requires 70CC heads, holly 500 two barrel carb, cast iron exhaust and intake manifold. I am also limited to .390" .410" lift. The motor will not turn more than 6100 rpm. I change the gear from a 3.73 to a 3.90 at the begining of the season and it still turns the same. The valve springs are all within spec, the lifter are anitpump up. It has a good coil and hei module. Am I at the max flow of the factory cast iron gm duel plane intake? I have been wanting to try more timing but have read many horror stories about hyper pistons not holding up. What should I try?
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The heads, intake/exhaust manifolds and carb are all fine to turn over 7,000 rpm. Whats the final gear ratio? how much timing are you running, you should be able to run 32-36* with good fuel and not hurt the pistons. What HEI parts are you running? The pick-up coil in the base of the distributor is just as important as the module. Eric -
I am running 35 degrees timing with 93 octane. The module is accel and coil is msd. The distributor is auto parts store brand. The gear ratio is 6.55 on a third mile banked oval.Comment
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Have you checked compression, years ago I had a SBC with a slightly bent valve that caused it to not hit the "peak" RPMs that it had before.
Also what is "spec" for your valve springs as those play a huge role in turning higher RPMs...my dad had this issue last season with his 355, it would hit 6200 max, a new set of valve springs was all that was changed and that same motor now hits 66-6800 with ease.Comment
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