Originally Posted by 68NovaSS
11:1 is pushing it for pump gas. You need more initial timing, start with about 16 - 18, vacuum disconnected and plugged, and maximum 38 degrees, all in by 2500 or 3k. If you have detonation pulling a load, back total timing down in 2* increments until it goes away. Have you checked all around for a vacuum leak? You're definitely running rich, 800 cfm is a lot for a street 383, but doable with a good tune. I have the same heads on my Nova, using the same plugs. I used 3933's initially, but now use RC12's as well. Short drives around the neighborhood can be a problem with fouled plugs.
Slow typing, BBR mentioned some of these points too...
I have an advance timing light. 16-18 degrees is way off the timing tab. I have to read it by turning the knob on the light until my timing marks are matched. I hope this is the right method. incidentally, should I set the total timing first at 2500 RPMs and then leave the initial timing fall where it falls? Mind telling me the gap on your plugs? I figured with MSD ignition I could use a wider gap of .045. Do you think that's too much? I have checked for vacuum leaks and found none.