Thread: Question about my holley carb..Bogs when I hit the gas..

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a mild 350 for street cruzin only needs about 450 cfm. a 600 holley will work fine if leaned out 2 steps down from out of the box. i change to the 50cc acc pump and use 62 to 64 primaries.
personaly for my sbc i like the 390 holley.

What shine said. A 750 is way too much carb for a mild 350 on the street. A 650 is bordering on too big and I ran a 650 DP on a fairly milld 400 and had to jet it down to 64's so it wouldn't run so rich.

14 inches at idle was the one above the throttle plate? What was the one below? The vaccum port below the throttle plate is exposed to manifold vacuum. It should be high at idle and low at full throttle. The one just above the throttle plate should be low at idle, high at slight throttle opening, and low again at full throttle. This is the one you want for vac advance. It may not be really low, it just has to be low enough not to actuate the vacuum advance. 14 inches low enough.

Okay, after thinking about this, do you think it might make the most sense to remove the over sized carb, and go with either a holley 600 electric choke, or a Q-jet new (from say a 75-75 model car with electric choke?? The original carb was an electronic q-jet, but I removed all the computer stuff, ect..I guess I could always sell the holley on ebay, as it does work, just a little too much so for my engine. If I installed the 64 jets, would that solve my problem? What about the shooter size?? I called Holley and they told me I need a BIGGER shooter.. I dunno about that. I sometimes hate calling the tech lines.. I called Comp cams 4 different times, and got 3 different suggestions for the same aplication..I sometimes wonder who is on the other end..

Check for a vacume leak, If that is all tight and it still bogs then try a list 1850 holley 600 cfm vac sec

damn and to think i need 750 cfm's

I like the crisp low-end response of a spreadbore on mild engines, because of the small primaries, and a used Q-jet is the cheapest way to test this. Then, if you want chrome you can upgrade to an equivalent Edelbrock (Carter AFB replica).

Holley used to make a spreadbore 650 double-pumper if you want that look and intend to run 8000 RPMs. If you want to simply romp the pedal without an finesse, you won't want a double-pumper, but one with vacuum secondaries.

i had a 67 stang with a mild 302 and a holly 650 dp.if i eased on the gas it was fine.if i dumped it it would hesitate its butt off.I figured iw was dumping to much fuel on the hard stomp so i chenged the shot squirter to a smaller size and i almost bulled e wheelie on me lol.problem was solved.

Originally Posted by jchrisd

Why 64? I am not sure what it came with stock, guess I will have to pull it apart. How did you come to this conclusion?? Just trying to learn.

3310 750cfm should have come with 72's up front and a 6.5 PV.

I run a holley 750 DP on my mild 350 and have no hesitation. Its all in the tunning. MY bud runs a proform body and front metering block reworked body to ~850cfm on his ford NA 302, radical cam and head setup and runs mid 11's all day long and as crisp as you can get. If you have some one local who can tune it for you Id stick with it. Bud thats just me.