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Discussion Starter · #1 · (Edited)
I've been having some strange issues lately. To complicate matters, the problem has shown up during final engine tuning, so there's always the question of "Did I bring this on myself?", but in this case, I don't think so.

Accelerating at about 1/2 throttle, power is there and then suddenly the power picks up and then it does it again (I have dual carbs). I've pretty well eliminated the vacuum secondaries as that system seems leak free and no parts are sticking.

I switched to the blue acclerator pump cam (more initial squirt; good for part throttle accleration) and a huge improvement. But I didn't need the blue cam before.

Researching power valves, all I can find is info on blown power valves, not sticking ones. Anyone know if a Power Valve can stick (causing it to open late or at reduced vacuum levels compared to normal) and if so, what symptoms do you get?

Currently, I have no black smoke during acceleration, so it's not running rich.

EDIT: I intend to check the fuel filters next, just to make sure I am not covering up a lack of fuel delivery.
 

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Power valves have a diaphragm, so they can't stick, only blow out. You may have a tear in the diaphragm that can't be seen. Replace it and see what happens, it may cure the problem. Make sure you have the right power valve as well. If it's to high or low can affect the running of the motor too.
 
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