I hope you’re making good progress getting this motor to run as you have hoped and here’s a rule to keep in mind.
As an example let’s use an engine with a 9.5 compression that has the needed good ring and valve seal and and due to that leaks down test at 3% or less hot.
If have it in mind to run 91 octane then your cylinder pressure should test out at 175 psi which would be safe even for a iron headed motor assuming a good state of tune from idle up to full throttle and max rpm.
If you want to keep 93 octane in the car then you should be safe with 180 psi of cylinder cranking pressure and very safe with 175 psi.
If you can’t get these cranking pressures with a motor having a compression of between 9 to 9.5 to one then you either have the wrong Cam in your motor as it relates to it’s compression ratio, or it’s degreed in wrong , it’s really that simple in terms of a high performance street motor.
If you find your motor leak down test at 10% or more then you will never have a high performance street motor, you will simply have yourself a fuel guzzler of a grocery getter / commuter car.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!
1) 1940s 100% silver 4 cup tea server set.
Two dry rotted 14 x 10 Micky Thompson slicks.
1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.
Education is what your left with once you forget things!
Last edited by steve25; 09-06-2025 at 03:25 PM.
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