Carb suggestion for my 383 stroker.

[montessaj]

I need help picking out a carburetor, I'm not really good at this kind of thing so I thought I'd ask you guys. I'd like to stick with a Quickfuel 4150 styled carb but what CFM should I run, 680 or 750? How about downleg or annular boosters? How about mechanical or vaccum secondaries? The car will see mainly street duty, with some drag/road race/ auto-x, but mainly street. I just don't want to buy this carb twice.

The motor is a 383 stroker:
10.1:1 Comp ratio
Aluminum heads with 64cc combustion chamber, 190 cc intake ports, 2.02/1.60 valves
An Edelbrock hydraulic flat tappet cam .488/.510 lift and 234/244 duration at .50 lift
And an Edelbrock RPM Air Gap manifold
I'll be running a 2400 stall converter on 700r, and the rear gears are 3:42.


Any suggestion would be really helpful.

Thanks, Andy.

Heres the link to my project thread: https://www.pro-touring.com/showthread.php?64115-Project-Nightmare-1982-Monte-Carlo-SS-(clone)-build

[kryptik]

I'd go with around a 750cfm (the 680 would be a tad small for your cam, especially if you want the car to see track duty). Annular boosters allow for better fuel atomization; they will generally increase torque and power in the midrange (this wouldn't be a bad choice for street use). With that automatic trans I would highly advise that you stick with vacuum secondaries...especially because you say most driving is on the street. I have a Quickfuel 680-VS carb on my GM zz383 stroker. The Reason I stuck with the 680 is because I mostly drive on the street, I have a milder cam than you, and fuel economy is one of my goals. It is a great carb, I personally like it much better than the demon it replaced.

[montessaj]

Thanks very much for your reply, I was beginning to wonder if anyone was going to answer! I think I will go with the 750cfm unit. I didn't know really what kind of difference mech/vacuum secondaries made. Thanks for the information!

[kryptik]

No problem Andy,

To further elaborate on mech/vac secondaries:

In a mechanical secondary carb, the secondary throttle blades are opened by a physical connection in the throttle linkage. This means that regardless of engine demand, the secondaries will always begin to open at a certain throttle position (Your foot directly controls the operation of the secondary throttle blades and metering circuits, whether it be on a 1:1 ratio or something else). In a street situation (especially with a lower-stall automatic), this can lead to "over-carburetion" because the secondaries will open whether the engine needs them or not.

In a vacuum secondary carb, the secondaries will open based on the airflow through the carb. In other words their operation is determined by engine demand. When airflow through the primary barrels is high, the secondaries will open to allow more air/fuel into the intake plenum. When airflow begins to drop away (due to high load, low rpm, etc), the secondaries close to restore primary metering. This is recommended for street use because the carburetor responds to the engine's needs. As a result, the engine generally has better street manners and better fuel economy.

[Nothingface5384]

800 cfm qjet off a buick 455 rebuilt /tuned for a chevy engine

youre chevy 383 should have a stroke close to a stock buick 350..john osbourne used to do this all the time and it worked great, but believe he called it quits last year..but i'm sure theires another guy or two that does this..
but easiest would be an off the self like a holly 750 4160 carb

[megaladon6]

x2 on the q-jet. you will want to go through it and do some mods (get cliff ruggles book on the subject, or just send it to cliff)
pretty sure they're cheaper over all, much more adaptable, and better on the street.

[Shaker455]

I need help picking out a carburetor, I'm not really good at this kind of thing so I thought I'd ask you guys. I'd like to stick with a Quickfuel 4150 styled carb but what CFM should I run, 680 or 750? How about downleg or annular boosters? How about mechanical or vaccum secondaries? The car will see mainly street duty, with some drag/road race/ auto-x, but mainly street. I just don't want to buy this carb twice.

The motor is a 383 stroker:
10.1:1 Comp ratio
Aluminum heads with 64cc combustion chamber, 190 cc intake ports, 2.02/1.60 valves
An Edelbrock hydraulic flat tappet cam .488/.510 lift and 234/244 duration at .50 lift
And an Edelbrock RPM Air Gap manifold
I'll be running a 2400 stall converter on 700r, and the rear gears are 3:42.


Any suggestion would be really helpful.

Thanks, Andy.

Heres the link to my project thread: https://www.pro-touring.com/showthread.php?64115-Project-Nightmare-1982-Monte-Carlo-SS-(clone)-build


I built & tuned a custom annular 850 on a combo very simmilar to yours but on a ZZ4 w/ E-Heads and same E-cam.

Perfect street manners and runs low 11's at the track on just engine.

[fuzznuts]

whats going to be your max rpm with your 383

[smhigh]

My Camaro has a 383, Trickflow aluminum heads 64cc, Edelbrock RPM Air Gap, 700R4, 4:11's.

Just had my Holley 750 with vacuum secondaries rebuilt by The Carb Shop http://customcarbs.com/

They suggested a 650 double pump or my 750 with vacuum secondaries.

Car runs great with the 750!