Carb recomendations for my 383

[bot0611]

Hey guys, got my 383 built las summer and kept my 600cfm holley on it but now i think it aint giving me a lot of power so im trying to decide and upgrade for a carb. 9.4 comp

im looking on theese.

Holley 4777S 650 CFM
Holley truck avenger 670 CFM
Holley street avenger 670 CFM

Now should i stay with vacuum advance?

Thanks for any feedback

 

[Hogback Fabrication]

What's the truck used for and how are you tuning the current carb?

 

[4X4HIGH]

Mid 650 CFM would be a good CFM choice but depending on how radical the cam is will determine vacuum or mechanical secondaries. Unless it was a drag engine though i would stick with a vacuum secondary carb unless the cam profile stops that from happening.

 

[GNERGY]

I had a 780 edelbrock on my 383 and had it dynoed and it was a perfect size. With the edelbrock performer intake and cam it put out 300 horse.
Tarey

 

[bot0611]

The cam is a Crower, 214 - 218 @.050

AS for the driving i drive it around the block just to move it and an ocasionall drive to the woods/trails around, no severe racing or dragging to it, would like to keep it on the slip side on gas, ive saw somewhere that a 750 would give me the pop to it but it would be bad on gas.

 

[Hogback Fabrication]

I'd still say a Q-jet is your best bet (which is either 750 or 800 CFM).

Best economy, best offroad performance, requires a little more tuning effort than a Holley.

Q-jets were the standard carb on pretty much every GM V8 in the 70's and 80's so they're pretty easy to find (in general, the earlier the better because emissions stuff was added to them in the 80's).


I'm running a Q-jet on my 383 (vortec heads, roller cam 214/222 @ .050") and couldn't be happier.

 

[DavidB]

Forget the holley ifit's gonna be offroad. You will hate it. Ask mike 330r

Do an Edelbrock/Qjet=same thing.

 

[pauly383]

If I found it right , advertised was 270/276 ? 1300-4200 rpm Cam ?

I say Q-jet too ( buy a stage 1 or 2 rebuild ) . And as for vac. advance , if its going to see street , and that cam says multi-purpose to me , I say yes . You want the part throttle economy ..... if you can keep your foot out of it , sounds like a fun one

 

[folkenheath]

I vote 670 truck avenger, keep the vacuum advance hooked up to full manifold vacuum and set the timing with the vacuum advance disconnected at 4000 RPM to 34 degrees then reconnect it to full manifold vacuum. You can tune it from there if you want but that's a good start. Your cam should have plenty of vacuum to operate the vacuum advance, which will give you better economy and part throttle response.

FYI, 90% efficiency at 5800 RPM(guess based on your cam duration and engine combo) is 578 cfm peak flow. I think the 670 would work well. I have a 780 double pumper on my 383, a lot faster than the 750 vacuum secondary, but I spin it to 6200 and it's in a 3200 lb car.

If you take it off road don't get the center hung street avenger, get the side hung truck avenger, much better for inclines. If you only drive it on the street you'll probably like the street avenger better. They're not picky on the accelerator pump setup without the check valves in the main well.

 

[yellowK20]

Jet performance Q-jet better than any Holley you'll ever find for street and off-road use better mileage too