HowDoIDriveStic

Hey guys, quick question:

Is a 750cfm 4bbl too big for my 383 stroker? I have noticed that I get about 5 mpg and the car seems to choke a little bit at wot. Is this a tuning issue or is it just over-carb'd?

hrspwr

iTrader: (3)

It really depends on your combo. If you combo is high revving than I would say a 750 would be good. If its just a street car with some WOT runs, I think a 650 would fit the bill nicely. You def need to tune the carb to your application.
My brother had a 350 in his car and had a 750 kicking around. He put it on and it ran great. Once the cooler weather came the car would load up and ran like a bag. Not sure if that is whats happening to you, but thought I would mention it.

bracket rs

iTrader: (2)

i tried a hp 950 on mine, ran good, more power than a 750, and drove good

bygddy

The math will say yes its too big. Reality says otherwise. 750 will be fine.
I use a 750DP on a 355 with good heads and a small cam , works flawless

jwfirebird

iTrader: (2)

needs tuned, dont believe the generic cfm calculators

86iroc2try

you could use a 650 and get better low-mid range torque. if youre using a 750, youll need to lean out the intermediate circuit and lower the jets, and leaning it out will make it drive better...not stumble...and pickup mph.

we always lean out stock carbs roughly 9%


for an idea of comparison...my 590hp 355 ran:
10.18 with a q jet
10.16 with a 650
10.15 with a 750

the 750 showed us the fuel pump was not enough, so we changed that and the gears and went 9s...but the 650 was just as fast as the others.

paul_huryk

Question is:

Is your motor a 325hp 383 or a 550hp one (or anything in the middle)? Makes a big difference in terms of driveability and mileage for your choice (type and CFM) of carb.

HowDoIDriveStic

Probably 325/somewhere in the middle haha

sonjaab

Most stock Rochester v-8 carb third gens are either 650 or 750
cfm anyhoo (from what I have read) so why bother with a aftermarket carb?

jwfirebird

iTrader: (2)

not really as simple as a 650cfm hole will make the engine go so fast. there are alot of adjustments. thats why i got a holley 4150 mechanical secondary, seems very simple to tune to me coming from the powersports stuff. if its rich or lean you just change the jets like a snowmobile. and you can buy a box of jets and squirters and all the other stuff you may want from holley and be able to make it do what ever you want.

best thing to do is get a book and read it a couple dozen times, all of the different carbs have them im sure

bestracing

I agree with above.

We had a 800 cfm on our 388 motor that we had in our 67 bracket car. We were actually over carbed but we tuned it on a chassis dyno making full pulls at WOT which is the only way the car was driven when not idling around the pits. Got the car pretty consistent just had to smack the driver in the back of the head a few times to make sure he'd stay consistent

The car had a 1.82 gear Coan PG trans, 5500 Coan stall, 4.88 gears. Ran 10.70's to 10.90's in the quarter at 121 mph. The motor wanted more cam than what we had in there.