Help with ignition timing

George,

You can put in one light advance spring. If this is the M/P electronic distruibutor then you can run full mechanical advance. I have a plugged vacuum hose on mine just for "looks".

I run my idle speed up to 2600rpm and dial in for a total of 36*. Set the dial on your light to 36* and when the crank timing mark and the zero line up, then tighten down the distributor. Back off your idle speed to whatever idle speed you prefer ( I run 1000rpm in neutral) and now check your timing. This will be your "initial" timing and I bet it is right around 12-13* (using the dial on the timing light- turning back until the two timing marks line up again).

I had my distributor "curved" by a pro because I discovered that the first guy who curved the distributor didn't fill in the advance weight slots so at 2400rpm it was at 36*, but at full tilt rpm, my 340 was advanced all the way to 48*!!
I now have a total mechanical advance in the distributor of 36*. I run my initial timing at 20* @ 1000rpm. Idles great, awesome throttle response!