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well, here's my problem my holley 750 cfm carb it's allway making my engine run really rich,my exhaust i vary smokey and when i punch the gas quilkly the carb pops. my engine is newly rebuilt it has a comp cam magnum 270H series cam with a 224 dagee duration and a .470 lift,edelbrock rpm intake manifold,G.M. hp heads with 2.20 intake valves and 1.60 exhaust valves,holley 750cfm carb, my compression is 9.73:1,

at first i thought i had a blown power valve so i replaced it,no improvement so i put a power valve plug in my carb still no improvement, i played with the mixture screws no changes. i put some new spark pluges in and readjusted my roller rocker arms, because i looked at my vacuum gauge is read around 15 hg but was vary bouncy wich indacates sticking valves or ignition miss,i reset my ignition timing to 12 drgrees. could my carb jetting be too big?

any suggestions would would be greatly appreciated.
 

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If you are running anything less than 360 cubes and/or less than 6000RPMs....yes, it's too big.

If you do not have alot of experience with carbs, my recommendation is to go for a simpler and easier to tune carb. Go for a Carter or Edelbrock AFB. And yes, I would go for a 600, but the 750 will go on with jet/rod changes.


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STEVE JACK
ConceptOne Pulleys and Brackets
Techical forum/links at www.inccn.net/techforum.htm
 

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I think what HOTROD was trying to say is that not only is the jetting too big, but the carb is too big for that motor. You really need to switch to a 600 or 650 carb.

If you keep running that carb, you will probably need to drop about 10 jet sizes to get any where near the right settings.

A bouncy vacuum reading usually indicates a vacuum leak or a miss. Most often, it is a vacuum leak, but in this case I'd say the motor is probably loading up on fuel real quick and causing the miss. Have you checked your new plugs?

Also, is this a vacuum secondary carb?

Best of luck,
Bill C.


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Bill C.
Colorado Springs, CO

68 Camaro... someday!
71 Chevelle SS
70 Nova
 

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i dont think its too large,

I have a 750 Vacuume secondary on my 67's 327 with a Comp280xe cam , th350 9.5:1 and a 3K stall, it works great. i'm running 68 jets with a 36 squirter, it runs great. but I gues it depends on the engine setup. the 650 I had on it was starving the car.

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