Does anyone know what carb, right out of the box, would be best for a ZZ454/4 speed muncie? I know that GM recommends an 850cfm, but I read somewhere that a 750cfm runs better. I have a 750 holley with mechanical secondaries left over from my last engine. Can I use that?

Mike,a 750 cfm Holley will be fine

Mike, if you had to buy a carb I'd say get that 850 vac sec. Since you have a 750 already, I would definiety use it. It will run REAL good with that!

When I was considering a ZZ454 from Salee Chevrolet, They recommended a 770 street avenger. I decided to rebuild my 396 instead, But decided on the 770 Holley street avenger for it, figuring if it was good enough for that engine it would be good enough for mine. It runs like a champ right out of the box. All I did was set the idle. I couldnt ask for more. My moto is if it ain't broke don't fix it.

I am running a 770 cfm avenger on my zz454 . Jetting 72/80 .
Plenty enough carb .

750...

Just for comparison.....I just ran a whole bunch of low 10.40's with my box stock 850 DP in a 540" motor..

HI i got zz454 it got holley 750 dp with pro form conversion goes like a raped ape
cheers victor jnr

Mike - I have the SA 770, but down jetted the mains to 70 because I was fouling plugs in 400 miles. Works great now.

Thanks guys. I think I'm going to run the 750 and see how things go. I love this site!

I am running a BG Demon 850 DP with annular boosters. It replaced a 4779 which was milled and drilled for the ZZ454 in my Elco.

My EC is lightened, runs a Super T-10W w/ 2.64 first, and 4.10 gears in the backyard.

The BG is hands-down a great carb for this engine, straight out of the box. I replaced the bow-tie RPM intake with an RPM Air-Gap, use 2" primary Hookers, and other than that the ZZ454 is stock for now.

The engine will pull from a dead stop in 2nd gear with zero bog, and in 3rd with some pedal work, but still no bog. It is very tractable in traffic, gets decent mileage, and the carb is very easy to set up.

These things are a combo of the BG design (i.e. adjustable idle-air bypass, etc) and the annular boosters. I normally build my own carbs, and have been a fan of annular boosters on at least the primaries for some time now.

Annulars are very interesting to watch as you wing the throttle, and they are far better at atomizing the mixture than the typical dog-leg or straight-leg booster in a normal streetable intake design.

They do, however, reduce CFM somewhat due to thier size in the venturi.

I have been a die-hard Holley supporter since the seventies, but I tried the BG simply because I wanted to do something different, and I couldn't find my annular booster tool to put them into the 4779 I had been running on this engine.

I was very surprised at the quality of the BG Demon carb, and at the adjustable features (something I'm a BIG fan of).

Bottom line: the car is faster, easier to tune, gets better mileage and is easier to drive in traffic than when it had the "dialed in" Holley. I'm not blaming the Holley at all- I'm just reporting that the annular version of the BG 850 Demon is a pretty good carb sitting on top of my ZZ454.

I posted some pics of the carb on my engine over in the engine thread section.
Eric

what is your fefinition of decent milage? :)

My definition of decent mileage is whether five bucks will get me to the beach and back.
With the BG 850 on the third day I can get there and back on 4 bucks. With the Holley it was 5 bucks every day.

I'm kinda practical about stuff.