[toolboxchev]

Originally Posted by gmc684x4

The thumper cam is your issue of tuning

Move your vacuum advance to mansfold pressure not on ported pressure

Here is an article i found that talks about tuning a thumper cam

https://www.hotrodders.com/forum/sbc...300.html?amp=1

I would try adding a Adjustable Vacuum Advance from Pertronix. It will give you more or less available timing at idle.

I have one on a 350 with 76 cc heads, I can run a lot of timing with those chambers, but I lose the top end.