OK, teen-agers, here is the classic HEI over-advancing/vacuum advance on ported vacuum source ping thing.
Start by having the mechanical curve set up to give 12 degrees in the distributor/24 degrees crankshaft mechanical advance. Shoiuld start about 900 rpms, limit at about 2500/2800 rpms.
Your 10 degree vacuum cannister is OK, but you need it connected tro full maniflod vacuum, not ported. Ported vacuum advance will add timing to the top end rpms, just where you don't need it. full manifold vacuum will draw the vac advance in at idle to help stabilize the idle pull against a torque converter, will drop off when the throittle is opened.
With all this done, set the initial idle timing at 12 degrees, then when done, connect the vacuum advance.
Your total mechanical degrees will be:12 initial, 24 added mechanical = 36 degrees.
Iintial idle timing is 12 degrees plus the supplemental vacuum advance of 10 = 22 degrees, just fine for an early 350 engine.
HEIs will over advance big time if not recurved, and if the vacuum advance is connected to ported source, then watch the ping monster take over the engine.
Give it a shot, should keep the detonation meanies away.
[This message has been edited by IgnitionMan (edited 05-12-2000).]