Quote:
Originally Posted by 69Cobra
I completely agree that every combo that runs fast enough to get hp should be torn down and pass tech. With that said, running 1.2 under with to small of valve would be like running to small of a carburetor. LOL Luckily for him this mistake saved his combo from getting an automatic hit. But will it save it from the review board at the end of the year?
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It is not the same philosophy or dynamics.
Also, the intake port does not behave the same way as an intake port.
The Chevy big block exhaust port and valve BBC are already bigger than they need to be.
Due to the lift restrictions in the class, using a smaller valve improves the curtain area by slowing down the flow and velocity.
During scavenging, the pressure recovery is better when the gases expand due to a slower velocity, specifically when you take into account the CID and RPM range limits of the engine.
Therefore, contrary to what many may think, going to a larger exhaust valve may slow down the car.
However, in the case of an intake valve, the rule would be the opposite.