Quote:
Originally Posted by jluetjen
Selecting the Appropriate Cam for Your Engine.
o For Autocross and DE use on an engine with carbs, MFI or individual throttle bodies, target an overlap of 60 degrees or less.
o For Full Race use on an engine with carbs, MFI or individual throttle bodies, you’ll want to target overlaps ranging from 40 degrees up to over 80 degrees.
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o If you have access to some key measurements, it’s possible to take these thoughts one step further by calculating your engine’s dynamic compression ratio. You can do this by calculating the swept volume from when the intake valve closes and adding any clearance volume in the combustion chamber, and divide this by the clearance volume. Typically the dynamic compression ratio for engines on pump fuel is 7.2:1 up to 7.5:1. For racing engines this dynamic compression ratio is generally more then 9:1.
While there are still volumes more that could be learned about the “black art” camshaft selection and design, hopefully you will find these rules helpful in peeling back the some of the mystery of selecting a camshaft.
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How does one calculate overlap on say a DC40 Cam profile?