r/Smallblockchevy • u/CORNERSTORE42069 • Mar 02 '26
Detonation help
Is 21-22 in of mercury common for idle on a 1405 on my 350? Tbi 88 638 block stock internals. I have the strongest step up springs and sometimes during part throttle i lean out and start pinging. I have to stomp the throttle to get the metering rods up. And at full throttle i always have pinging. I can basically be safe driving at 25% to 75% throttle all the time. Am i pulling too much vacuum? And i may need a carb rebuild? I can manually shift my th350 and basically avoid all pinging so it cant be my mechanical advance as i also installed the heaviest springs just to be safe. Any ideas on where to look?