Well my dramas are continuing and I'm getting a bit discouraged.
I have a knocking sound that comes and goes and causes the motor to run rough when it's knocking, then smoothes out when it's not knocking.
I've systematically removed each plug lead to try and identify which pot is dropping, but without success. On a test drive the motor backfired a few times when the knocking occurred.
I've heard that pre-detonation (pinging) can be misleading and sound a bit metallic.
I've recently changed my lifters and the feet to my YT roller rockers as a result of having too much lifter preload for the last 2 years. I've also had to remove about 30 thou from a damaged valve tip, (see the following thread) . . .
Warn valve tip.
After making these changes, the motor was smoother and ran the best it ever has, but this happy state only lasted 2 days before the weird knocking sound and associated roughness developed.
The 351 has 302 heads with flat tops and runs straight gas thru an Impco 425. The initial timing is set at 10 degrees and I've had the vacuum advance removed. The dissy has also been re-curved to suit gas.
PS - I'm not sure if this is related, but since I've had these problems, the motor is a bit harder to turn over when starting, as if there?s a spot where it is harder to turn, instead of turning over smooth like it used to be. (The battery is only 1 month old and cranks over 600A)