Several of these old Volvos I've had, ignition timing was seasonal thing. In winter, for easy starting and cold running. In summer, to avoid knock and ping.

Yeah, I know it ain't right. And it wasn't all cars. But with some, that's just what the motor liked, and it only takes a half minute to twist that distributor clockwise a couple degrees. You can always put it back.

In fact, I used to keep that adjustment bolt slightly loose.. tight enough that timing wouldn't change on its own, but just loose enough that I could make quick adjustments... often times, while waiting for red lights to turn green (as a pizza driver, I knew the duration of red for every light in town)

George's suggestion first... if it goes away when you pull the choke a tad, it's lean.

Maybe you don't have the ideal needles in your carbs. All needles are going to be about the same diameter at idle, but if yours are too fat at a half inch down, that'd cause a lean mixture when you step on the gas. Maybe needles with a greater taper would work. The folks at Z-therapy should be able help in sorting that out. I've never had them do any work for me, but I've bought parts from them, and always felt them to be be most helpful.





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-Matt I ♥ my ♂