have a 12mm mains want to turn to 4000 plus rpms and do it safe. any tips, basically something durable thats not gonna break the bank.

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sorry 14mm block 96

 

have you crank, con rods, and pistons balanced together.

 

Balance the whole rotating assy. When we balance we also do so with the harmonic damper and the flexplate or flywheel on the crank. Better overall result.

I think for 4k you should be fine without a girdle, the main studs is a good idea though.

 

what do you need for 5000 rpms

 

You can get 5k springs for your pump, But a factory 12mm p-pump turned up with all the goodies is goin to be at its peak for making power at those rpm's. If you were to jump up to a 13mm pump you would bennifit at those higher rpm's. But get everything balanced, run a fluid dampner or ati. You dont really need main studs or a girdle for 4k but for more 12mm main studs and a girdle or block stiffner would work, For what you are doing 14mm main studs would be over kill unless your block takes 14mm already.

 

mains already 14mm was thinking about a stiffner that goes across oil pan