Reply to "Ignition Question"

First, 10-1/4:1 with iron heads is too much compression for todays so-called 91 octane "premium fuel. Indeed, 9-1/2:1 is pushing it unless you use avgas. Second, all the advance totaled up should not exceed about 36 degreees: initial setting plus mechanical plus vacuum, even though they occur at different times. There should be a rubber bumper on a post in the distributor that is supposed to limit centrifugal advance; if it fell off or split, the mechanical advvance will be far in excess of what the engine needs. Finally, I think it would be a real good idea to pull your distributor and check the drive-gear roll pin. This pin tends to shear a little at a time in some engines. When it does, the timing retards as much as 15 degrees, which also affects engine temp. Don't just look at it; look THROUGH it to see if the pin is bent. The fix is to replace the pin with a real roll pin, not a spring-pin, then add a second smaller roll pin inside the first one to reinforce it. Your roller cam probably requires a bronze distributor gear that often wears out in 2000 miles, retarding the ignition on acceleration and advancing it during slow-down. These gears are consumable items like cam chains. When you chech the drive pin, also check for a worn-out gear with razor-sharp teeth.