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Timing Curve Advice
Noticed lately that the truck had been running progressively poorer and fuel "economy" was falling off as well. Did a pretty solid tune up, rebuilt a carb I had on the shelf and installed it, did plugs, wires, inspected HEI for wear and degradation, and hunted for vacuum leaks.
During the process, I found that my adjustable vacuum advance can wouldn't hold any vacuum at all. Replaced that with another adjustable unit, reset my initial (to the same value I had set it to after purchasing it) to make sure it was dialed, and the truck is running very well overall. I suspect the new carburetor needs dialed in a bit, but I also don't think that's contributing to the issue.
Problem is, it seems to get a slight and short-lived ping when accelerating from cruise under certain conditions. I am of the opinion that I need to tweak the mechanical/centrifugal advance to come in a bit later and leave the vacuum advance tuning alone. It's running very well as is, and the detonation is very slight, but ideally it wouldn't be there at all.
Opinions?
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