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What is a good starting point for jets on a Holley 750 double pumper? Engine is a 396 .030 over, torker intake,HEI,.570 lift cam,roller rockers, headers, dual 3" exhaust. It seems to run way too rich, tail pipes are sooty black and smells rich, plugs dont look too good for a fresh rebuild. No idea of carb internals and I am new to Holleys, just need a starting point.Thanks.

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I cant really guess as to which jets you might need but my best recommendation would be to have an oxygen sensor installed at the collector on your headers and buy an aftermarket air:fuel ration guage and go from there. That would be ideal but if you dont have that kind of time/money/desire (it would probably cost less than $125 total) then remove the float bowls and find out which jets you have, then reference that to which jets that particular carb should have. if they're the same or close, buy new jets about 3 sizes down and try em out.. its really a guessing game. If the current vs. stock jets for that carb (not engine) arent the same, Id probably try those first...

Mike Reeh
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The factory settings are a good place to start. The 4779 had 75 and 76 respectively however the 4779-1 and -2 had 70 and 80. The 4779-0 and -1 had 8.5 power vavles while the -2 had the 6.5 vavle. Hope this helps.
 

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Can you tell me where I can get new smaller jets for my original Rochester 2GCV carb (72 Chevelle, 307 engine). I have the same problem with my car. Thanks!
 

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bigyellow, I just got that same carb. It came out of the box with 72 jets front/80 jets rear.I haven't run the car yet though.So, I can't say if this is going to be the right combo. I was told that with holley dblpumpers using a power valve, the rear jets should be 8 to 10 numbers higher. And if you plug the power valve run all jets the same.I don't know how true this is.Anyone have an opnion on this?

–Joe–
"67 Malibu"





[This message has been edited by Joe454 (edited 07-11-99).]
 

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I was told that Holley calibrates their carbs. at 70 deg. and at sea level.
 
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