Hi anyone know what CFM carb is reccomended for the ZZ4 355HP motor?
I am looking at the Holley street avenger 670CFM or the 770CFM model...what would work best for my new motor?

THANKS

Depends. I've heard so many different cfms for this engine... I had a 750 on mine and was fouling plugs even when it was leaned out all of the way. But I think the 355HP results came from a 750 on it (salleechevrolet). I have a 600 on it now, and its perfect. I know there are a lot of people that use the CFM formula to get you in the ballpark. If you use that equation you get:

350 x 5800RPM (max HP) = 2030000 / 3456 = 587cfm -and thats if this engine was 100% efficient, which its not, so according to this you can even have less cfm.

Keep in mind GM rates those engines to SAE specs. So on your tyical engine dyno they probably put out more like 375-380 (like if you were to read a dyno test on it in a magazine). On the local chassis dyno they often put down in the low 300s at the rear wheels through an outomatic trans, which would indicate a smidge more than 355 at the flywheel.

A 750 should be no problem. A larger carb shouldn't automatically make things run too rich or too lean. It's all in the calibration and making sure the carb is in good running condition to begin with. Given that the motor comes with a dual-plane intake (which often like slightly larger carbs) I wouldn't hesitate to put a 750 on it.

My friend has a very modified ZZ4 (430+HP)and runs the 670 street avenger and works perfect out of the box.

That 750 that fouled my plugs was brand new, i took it back to jegs, got a replacement, and that second one fouled the plugs just the same. (Leaned out all of the way). A 600 made the plugs nice and brown. I'm not claiming I have a fast car by any means but i raced two Blue Suburu WRX Turbos w/ the gold wheels(their fastest, which happen to be 13.0 cars) and I had the upper hand. If i could claim 12.9 i'm happy. thats with the 600cfm. I'm not saying its the correct choice for a ZZ4, but the 750 didn't work out for me. I would assume the 430 HP with a 670cfm wouldn't be worlds different than a 355HP with a 600. I should be around 410-420 so i may check into a 650.

buy a q-jet and learn how to use it. You;ll never go back.

Hi anyone know what CFM carb is reccomended for the ZZ4 355HP motor?
I am looking at the Holley street avenger 670CFM or the 770CFM model...what would work best for my new motor?

THANKS

GM sells the correct carb for the ZZ4 which is a Holley 750 with vacuum secondaries, PN 12485506. This is right from the GMPP catalog on the ZZ4 parts page.

Hi Thanks Guy's i went for the 670CFM most all carb places i called said a 650 would be good for it so i though 20 more CFM would not hurt.

How much did you end up paying for it? Super Chevy, Car Craft, Chevy Hiperformance...(I don't know, but it was one of those) did a carb test on an engine (can't remember exact engine size) but they used the same engine set up for each test and only changed the carbs for each dyno run. Every carb (600, 650, 750, 850, 1050?) gave almost the same results on the dyno, expcept for the carbs under 600cfm. I think as long as your carb has more cfm than the CFM formula states you must have as a minimum, youll be fine.

How much did you end up paying for it? Super Chevy, Car Craft, Chevy Hiperformance...(I don't know, but it was one of those) did a carb test on an engine (can't remember exact engine size) but they used the same engine set up for each test and only changed the carbs for each dyno run. Every carb (600, 650, 750, 850, 1050?) gave almost the same results on the dyno, expcept for the carbs under 600cfm. I think as long as your carb has more cfm than the CFM formula states you must have as a minimum, youll be fine.

That was in Chevy High Performance. And with each increase in size the engine gained power, it did not stay the same until the 950 was tested. From 390 to the 830, the engine gained power, maxing out with the 830. The 950 neither gained nor lost, but maintained the power level of the 830.

Carb Test (http://www.chevyhiperformance.com/techarticles/148_0403_seven_holley_carbs_test/index.html)

I take those carb formulas with a grain of salt when it comes to making maximum power.

The ZZ4 makes its rated 355 HP with a Holley 750 according to the GMPP catalog.