Ok, I need some help from you all that are better at non-stock carb/motors. I recently bought a 69 Camaro with a stock ZZ4 350 crate motor in it. It has a 750 Edelbrock carb on it and I have been unable to tune it well so it is drivable, never have had one of these and don't know anything about them. It runs, but just stumbles off idle etc. so I just thought I would replace it with a new holley 750 because I really just like holley carbs better. Before I spend the money, just for the heck of it I pulled the stock holley off my 65 vette 327/365hp motor and amazingly, I think the ZZ4 runs better, good low end response and much better idle and starts much better. If I remember right the holley is less than 600cfm so it is probably under-carbed for the ZZ4 but my question is this: Chevy suggests a holley 770cfm carb for that engine but I am concerned that might be too much for a street car that I want to have as a nice driver, not a strip car. I am wanting to stay with a holley and could go with a 600, 650 or 750 double pump or vacuum. If anyone has any experience with this engine and carb selection that would be great, motor is backed up by a 5 speed trans and is in a 69 Camaro.

 

I'm not sure about that engine but the most common mistake is putting to big a cfm carb on an engine. The Edelbrock carb is a Carter design that they had bought the rights to long ago when Carter got out of the carb business (I believe it's the AFB design if I remember correctly). They were originally used on Mopar's and worked very well if you know how to set them up. They might have been used on other makes as well that I don't know about.
A vacuum secondary is usually used on an automatic trans car, not a manual, if that helps with your decision any. Although I've seen people use them on about anything, me included, if it's the cfm that your engine needs. The one on your Vet is most likely a 600 cfm and if your engine did well with it overall I'd try a 650 cfm and see how well it runs with it.
Hopefully someone on here can tell you what works best for them on that engine set up. I hope that helps you some at least.

 

If you like Holley's....
Goto Holley's Interactive Carburetor Selector tool...
Holley Interactive Carburetor Selector
and answer a few questions.

 

6T9, Thanks for your note. I am leaning toward the 600 Holley just because I know it will be a good street carb, might not be as strong over 5,000 than a 650 but should be better on low end response.

 

Hi Craig,

I'm not up on the newer GM Performance motors, but what I've found out about the ZZ4 crate motor is, it's a good, popular performance motor and it looks like it is sold with a 750cfm carb.
I put a Holley 750 vac secondary carb on a mild 355 I had in my 68 Camaro and I loved it. I first did all the math and it said to use a 600, so I put one on and it was just ok, but when I put on the 750, it really woke it up. From what it looks like, the spec's from the ZZ4 were pretty close to the 355 I had, except my motor used a hydraulic cam where the ZZ4 is rollerized.
Like stated above, with automatic's the general rule is a vacuum secondary car and a double pumper for stick cars, but like also mentioned above, my car is automatic and I use a double pump.
I think with that motor, a 750 would work just fine.

 

Bruce, thanks for your input and what I have found is very close to your experience. the stock 600 vacuum secondary has great off idle response at low rpms but falls off about 4000 rpm. I them put on a 750 double pump that is set up as a race carb for a 406 motor that is jetted a little to big for the 350 and I lost some of the off idle response but the motor really woke up over 3000 rpm and pulls noticeable harder that it does with the 600. I am leaning toward a box stock new 750 vacuum secondary and hopefully have the best of both. Thanks all for the input.