I have a gauge that tests both vacuum and fuel pressure (Sears), but it's probably at least 55 years old (got it when I was 15 for working on my '57 Buick hot rod). Perhaps they still make such a thing.
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I have a gauge that tests both vacuum and fuel pressure (Sears), but it's probably at least 55 years old (got it when I was 15 for working on my '57 Buick hot rod). Perhaps they still make such a thing.
again, unaccounted for rpm changes can usually be attributed to carb issues. As previously mentioned timing advance/retard can do this quite effectivly !!. . trust your guages ..... if your vacume indicates low figure that one out !! ...... especially if it's verified or a good guage like a smiths or something.
keep us informed
Look down the throat of your carb while the engine is running and blip the throttle linkage. Does the carb's accelerator pump squirt some fuel or does it not and as a result the engine RPM drops and/or it backfires in your face?
My original Zenith carb had this problem, and the replacement Chinese Zenith knockoff developed it too. Installing the single bore Weber cured the problem and the truck no longer stalls when I try to pull into the intersection from a red light turning green.
Quick update on this thread....
I can't believe I missed it, but I finally (with some help of a 2nd set of eyes) noticed a pretty massive fuel leak coming from the outlet of the pump. A few turns of a wrench and it went away. That really helped the reving symptoms. I also discovered a hole in the boot that connects the vacuum advance to the carb and I repaired it with Sugru. The engine needs to be timed before it will run well... but the starter died during all that cranking when it died. So now I'm waiting on a replacement.
stabbing the gas and having a duuhhhh moment is usually the power piston (aka accelerator pump) ........... followed by timing.
good you spotted the fuel leak but the power piston will initalize the rpm jump and whats in the float bowl will run it till a lack of supply catches up ..... IE' your leaking fuel line from the pump.
sounds like you have a handle on it?