The distributor in my 1980 Aspen has 20 degrees of mechanical advance. The vacuum advance unit gives about another 20 additional. With the vacuum unit adjusted to give the slowest advance rate possible, I have to run ~6 initial to avoid detonation at part throttle above 50 MPH. My mechanical curve starts at ~1300 and is all in by 2200. Now the question(s):

I would like to run more initial timing for better off idle and low speed performance. I partly welded the advance slots on a spare distributor advance cam. I need to finish the cam to give the total timing I want in the distributor. I would like to try running about 15 or so initial. I will build the distributor with an advance unit that gives about 5 degrees less advance (15 instead of 20).

My questions are: what initial timing do you use and what kind of advance curve are you using? My compression ratio is about 9.5:1 on a stock 1bbl, the stock camshaft is advanced about 3 degrees and I use 93 pump gas. I currently average about 23 mpg.

Thanks

Mitch

My guess is that 10 - 12 degrees initial would be about right. Most my street slants run 6-8 degrees on regular (87 octane)

Try turning-up the advance to 15 degrees and see if the engine likes it, most will start to idle rough with that much initial.
You are on the right track, get an extra distributor (or two) and try different combos until you find the best one for your car and driving style.
DD