engine seems to stop reving for a moment

Old 10-18-2010, 07:04 PM
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Default carb problem

hey cepx put vacum guage on engine and it reads between 5-8 inches at idle (in low gear) gave it a little gas and it just stays around the 5-8 area.. im gonna try one more time with a 4.5 power valve. the other carb had a 6.5 in there for all these years and the car ran like a clock. im rebuilding that carb this week and its going back on. in the meantime i want to see what the problem is with this carb(if the carb is the problem,) as it will go on my 377 engine next season and i would like it to be right. the 84 square is just about correct for the carb(without power valves in front and rear. some of the stock 750s out of the factory are 75-75 square with power valves in the front and rear. some have smaller than 75 in front and 75 in rear(with power valves in front and rear, so by removing the valves in front and rear and going up 8 sizes it comes in at 84-84. when imgot the carb from my friend it was done without the valves and was 83 front and 84 rear. thats probably what i will go back to when i take out the front power valve, like you suggested. my buddy, who is a super stocked and stocker racer in nhra told me today to get that power valve out, just as you said i should do. i can put bigger air bleeds in the idle circuits if it loads up in the pits. quick fuel told me to do this. so did you,, so i respect all that you are telling me.. holley tells me its definitely not the carb, but the fuel delivery system( elec fuel pump or filter or pressure regulator) but i dont believe that. what do you think thanks art
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Old 10-18-2010, 11:38 PM
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Well chevyart, sounds like installing a 4.5 PV would be a complete & total waste of time if a 3.5 didnt work.
Now dont get me wrong, I'm all for baby steps when it comes to tuning but sometimes you can get hung up on too many small changes and get frustrated (you sound frustrated) .
Bite the bullet, make a profound change, you can always go back, if that 6.5 was working in the other carb - I'm gonna go out on a limb and say it will work in the new one.
So stick that 6.5 in there or better yet plug the hole(s) jet up accordingly (not 8 either, more like 5-6) and be done with it.

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