[Tom Wells]

mdross1,

Hmmmm.....

Without going on a hunt for the exact figures, here's what my memory says: 12 degrees initial (maybe it's 11?) and 20 degrees centrifugal (maybe it's 21?) for a total of 32 degrees, all in by about 2500 rpm.

This is on the 521 with a hydraulic roller cam and EFI. The distributor is an MSD and has no vacuum port. The computer does not control the spark timing - it is entirely controlled in the distributor.

On my next engine, a 557 similarly set up but with a 950 cfm Holley I plan to use about the same advance figures. The biggest difference is that because I had to use a Motorcraft Duraspark distributor due to hood height problems, I will be using the vacuum advance also, limited to about ten extra degrees at part throttle. The extra goes away when the throttle is opened significantly.

I have a Holley 950 cfm carburetor with no spark port and no vacuum port for the PCV so I have ordered another base plate for it that does provide those ports. Perhaps you could get another base plate for your carburetor to add them too?

Tom