a week or so ago i put forth the question on this forum, about the timing for a 1982 351w engine i had rebuilt, i recieved back the answer that the timing should be about 8-12 degrees btc, my question is this, why if i set the timing anywhere even close to 12 degrees btc does the engine run slower and if i step on the gas i get a pop back thru the carb, if i set the timing around 18 degrees btc the engine runs fine, smooth, no back firing or pop backs seems to have plenty of spunk? the cam i have in it is a comp extreme energy cam made for hauling or towing. i seem to remember on my 75 f250 that i had installed a 1972 351w into, the timing was supposed to be at 12 degrees btc, so i don't doubt the 8-12 dgree recomendation, but whats up anyway?

 

it sounds like your harmonic balancer ring has slipping.. kind of common. You need to find TDC on the #1 cylinder, mark it, and then measure out 10 degree, or get them stick on tape from summit.. Or replace your balancer. If it has slipped, it might be time for a new one anyways.

btw, you did pull the vacuum hose from the vacuum advance on the distributor, right?

 

Bremen you may be correct, I had that happen to me once about 23 years ago.