oldxr

If I measured the base circle on the old cam and the new cam and figured out the difference and added or subtracted this to the length of the original push rod would this be an accurate way to calculate the push rod length?Example-base circle on new cam is .010 smaller-use .010 longer push rod than the original ?

A.R. Shale Targa

iTrader: (2)

If you've changed nothing else like heads/gasket thickness or rockers then in theory you have the right idea. The factory lifter plunger has a pre-load range of roughly .020" to .120" before it bottoms out and becomes a solid. I'm pretty sure GM shoots for about .100 depth so your .010" base circle change won't matter if running a stock length pushrod. 7.385" is considered stock and most cam swaps where only the cam is changed and lift ends up in the .550"-.600" range use a 7.400 length aftermarket 5/16" diameter .080" wal thickness

svede1212

iTrader: (3)

If the base circle is .010" smaller then the difference is only half that or .005".