[Rob Doe]

Gulf, I'd like to add the following points:

IMHO, when running a high compression head on the Model A, it's important to know exactly where your car is initially timed. What I'm referring to is: It is easy to unintentionally time the car at different numbers of degrees ATDC.

I use a test light to determine how many notches down the quadrant the light comes on after tightening the dist. cam lock screw during the timing process. Generally, it comes on at the second notch down, but I've had it be 1 down also, and 0 or 3 at least once each. The light comes on when the points open. When estimating your advance you would subtract the number of notches for the actual points opening from the quadrant settings.

Our coupe has a h/c head of unknown ratio. The compression tests 110, 110, 110, 115 on 1-4. I have been told it is likely the 6:1. After much effort hunting down vibrations, rattles, tinkles and yes, knocks, our car is now quiet. I originally thought the engine had a rod knock at about 35mph on level roads. But, after replacing the motor mount rubbers, working on the spring tension at the front mount and tightening a lot of fender, shock, etc. bolts, the spark advance location at 40-45mph matches Bidondes' graphic exactly.

Hope this helps, it's been a 2.5 year search for the "Model A Experience"