carb size for ZZ4??
Ok, I need some help from you all that are better at non-stock carb/motors. I recently bought a car 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 65 327/365hp 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.
-
-
Re: carb size for ZZ4??
Craig-----
A carburetor with a rating of 500 CFM is the most you would need for a ZZ4 engine application. In general, a street engine will run best with a carburetor sized for the application. If you use a larger carb, you definitely want one with vacuum secondary operation. However, even in this case I would not recommend anything more than 600 CFM.
Using a Q-Jet can get around this. Most Q-Jets were in the range of 750-800 CFM. However, their air valve secondary operation combined with small primary and large secondary bores made them work well on engines for which a much lesser CFM rating would be optimal.In Appreciation of John Hinckley -
Re: carb size for ZZ4??
I bought a Holley 650 square bore double pumper for my ZZ1 crate engine which is installed in my 1970. My ZZ1 crate engine was available before your ZZ4 and has a high rise aluminum intake compared to a LT-1 factory intake. I like the double pumper to have/maintain complete positive control over the opening of the secondaries. With the HEI ignition there is a loss of the factory tack hook up. I like the ZZ1 with the increased horsepower compared to my original 350/300. I used a Holley 650 spread bore double pumper on the 350/300 for many years. The spread bore 650 double pumper would not work on the ZZ1 without using a adapter. Using an adapter would not work, not enough hood clearance.Comment
-
Re: carb size for ZZ4??
Enjoy your Holleys. IMO, if you worked with the Edelbrock some you would end up with a far less trouble some installation. For it to not work well means it just needs a little TLC, while the Holley you will have to play with all the time. I don't believe in any carb that has a gasket surface below the fuel level. I've seen so many leakers in my day that it scares me.
Stu FoxComment
-
Re: carb size for ZZ4??
I have a very simalar setup in my 74. I am running a Holly square bore 650 dp, as it is a 4 speed. If it were a automatic I would go with vacuum secondaries. If you are running a cam that alows high rpm ( 6500 plus) I would go with a 750 cfm carb. Holly's are much more user friendly to make adjustments and tune than the EdlebrockEd DiNapoli
CNJ Chapter Past Chairman/Co Founder
1972 Targa Blue Coupe, Original Owner,
Duntov Award, Sam Foltz Award,
Founders Award, NCRS Gallery VIII
2011 Corvette Convertible
NCRS Presidents Award 2014Comment
-
Re: carb size for ZZ4??
Craig, I just put a ZZ4 engine in a friends 80 vette and we used the Edelbrock manifold and Edelbrock spread bore carb. its a perfect match with the engine. this package was all purchased from Scoggy-Dick. The Edelbrock Carb. looks just like the factory Quadrajet. And Everything just fits under the stock hood. you'll need a thin carb. Base gasket. The good thing about Edlebrock Carb. is the small primarys for normal driving around town and the big secondaries make the engine fly when you step on it.New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight.Comment
-
Re: carb size for ZZ4??
My '69 Z/28 was born with a 780-800CFM vacuum-secondary Holley (to make SCCA happy), and that was great between 6000-8000 rpm (but how much time do you spend up there?). When I had the original Holley #4053 restored, I put a 600CFM vacuum-secondary Holley on it (I keep two of those handy as "shop" carbs) for two months, and it was much more driveable, with crisp throttle response. A 600 vacuum-secondary Holley would be a good choice for your ZZ4.Comment
-
Re: carb size for ZZ4??
One of the other old guys around here just built a glass Chevy coupe and put a ZZ4 in the engine bay for cruising and a stomp down once in awhile. Larry had a 600 CFM Holley on the shelf, rebuilt it and it runs very smooth and has good acceleration. Rear is either a 336 or 355.Comment
-
Re: carb size for ZZ4??
Thanks everyone for your comments, I agree with the spread bore comments but the existing 750 is a square bore and I am not interested in changing the intake or using an adapter so I am going on the safe side and order a Holley 600 and call it good, rarely spend anytime over 5,000 anymore so although a 650 or 760 might be more fun up to 6,500, around town diving is the priority.Comment
Comment