neuroclast

I'm planning on replacing the Q-Jet I have now with a new carb, but I'm having issues deciding on which to get. The 383 is mildly modified, ~460 crank HP, and I have a 700R4 w/2800 stall and 3.55 gears. I was thinking about going with a 750 DP like everyone else, but I've read that I should be using vacuum secondaries on an automatic.

Any opinions on the matter? Should I go less than 750 CFM, or bigger? Open to all suggestions at this point in time.

-Josh

jdunne

Josh, my 383 ran very strongly with holley 750 vac sec.....slightly more hp,700r4 & 3.08....very good economy which was surprising....ran like a cut cat with the pedal down,so didn't seem to lose any performance with the vac sec.....regularly revved to 6800rpm with buzzes to 7200rpm.....john

Rab16

Your setup sounds alot like mine, I got a Speed Demon 750 DP. I wasn't sure about the mechanical secondaries at first but when I step on it and the engine roars to life I know I made the right decision.

neuroclast

I'll assume you have an auto.. Do you have any issues with it stumbling or anything when you get on it? My 700r4 likes to lug around at like 1500 RPM when the TC locks up. I'm really wondering about the mech secondaries on an auto, when even the Holley website strongly recommends vacuum secondaries.

11Jake

It depends on what kind of driving you want to do?
I have a 383 with about 500hp with an auto trans.
I had a holley 4160 with vac. secondaries with an electric choke. Very streetable acting motor with plenty of power.
I have since installed a Holley 4150HP carb. with no choke and mechanical secondaries. A real bitch to keep running until warmed up (no choke), but when the motor is warm it idles a little better then the 4160 did. It has a better thottle response and I got a little more power with the 4150HP. It also has a price tag double at $600
Hopes this helps!
Jake

neuroclast

75% street / 25% strip. I've found lots of used 750 DPs (4779's) for <$200 that I could use which is why I was condering that. I was mainly curious how the mech secondaries would work out on my auto.

SanDiegoPaul

I used a 650CFM AVS from Edlbrock. Great streetability and it seems to be holding the dyno tune much better than any previous carb I've had.

11Jake

I have never used the 4779 carbs, so I can't give you my personal opinion. With the two Holleys I used, the 4160 and 4150HP I can say that if you are planning to go to the strip I would definitely go with the 4150HP. That is the reason I switched to the 4150HP for some occasional strip time. My 383 is a massive torque monster with an auto and it loves the mechanical secondaries more then the vac, secondaries.
Good Luck with your choice.

Rab16

Yes it's on an auto, and also still a work in progress but the end product will be a 500ft/lb 383 with a 2800 stall, 700r4 tranny, and 3.55 in the rear. The mechanical secondaries give a little better response but sometimes it seems like even though it revs up quicker the power lags alittle. Not sure if this helped...

C3 Stroker

Your set-up is similar to my previous 383......best carb for me was a Mighty Demon 825. Best horsepower and driveability. The Edelbrock 800 also worked well, but did not outperform the Demon.

hobby0002000

Go with a 750 speed demon annular discharge booster with mechanical secondaries.

gingerbreadman1977

im with you rab16. i love my demon 750 DP

neuroclast

Is the Speed Demon that much different than the Holley? Both 750 DP right?

hobby0002000

Both are good carbs, if you go to the demon carb website and read about them, they will say that the speed demon model is for a certain duration cam at .050( something like 220 to 240 duration from what i remember) and the mighty demon is for bigger duration cams at .050 duration etc, to help in your selection. Also select the annular booster model. You have enough cam,compression,converter,heads,gear,and cubic inch to use a 750cfm carb

gkull

how big of carb depends on your intake manifold. On An open under the butter flies dual plane or a single plane requires less CFM


I'm a fan of less cfm is better for driver friendly. All you need is a 620 or 670 VS with a higher flow dual plane

I used a 750 Edl VS on my 355 and high end 383 and switched to Demon 750 DP I still use a 750 DP on my 434 ci and don't feel carb restricted