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Carburettor Opinions


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2:45 PM
Jul 20, 2008
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I am looking to replace my Holley 650cfm Vacuum Secondary that is sitting on my 383ci with a 750cfm Double Pumper. What is the best DP to buy?
That boils down to a Holley or Demon. I have not used a Demon but I have used a Holeey Dp and liked it alot.
Takes a lot of motor to swallow what a DP has to offer. Make sure you aren't looking at to much carb.

I guess i should have narrowed down the question.

I Like Holleys, but which DP, there is street carb DP, there is crace carb DP., Holley HP and Holley UL TRA HP (all offer DP)

SO thats kinda what i wanna know, what "style" of DP is the best to get?
If your set on a DP, then a regular 4150 DP will do it for you and do it well.
It depends on your combo as which DP to run but like was said the basic 750 Holley DP swill work good on many combo's. We run one on my sons 400 Dart and he loves that carb. 11.40's @ 117 and he tried an 830 carb which ran no faster then the 750. Ron

I got a 4 speed hurst behind it (833). Mild Cam (pretty much stock). A engine builder from the states said a 750DP would be a natrual fit on a 383. My engine builder ran a 750 on a 308ci and it went better then it did with a 650. Alot of people have agreed that the 750 would give it that "little bit more". 383 having alot of vacuum the 650 would be kinda small.

Just wondering now which 1.

1 guy said 82751 HP 750 holley (i assume thats the 4150 series HP street) and an engine builder thats built engine after engine (512 strokers etc etc) has said a 750 Dominator would be awesome but would require a new manifold from the stock 1 I have, otherwise, he also suggested 82751 HP 750.
HOly crap, what a bunch of wild recomendations.

An HP Holley!, a 750 street Dom.! Yikes!

Let me get this straight. You have a B series engine, a 383 with a slightly warmer cam than stock and a 4spd trans behind it.

OK, with that squared away, I and we here need to know what else, to the engine is there done to it. Otherwise, we assume stock besides a mild cam.
This is important. VERY. Because if your local builders and such are recomending these carbs, I'm wondering if there stuck on race or just wacko.

I'm not arguing the cfm of there recomendations, just style of carb. A regular 4150 750 DP (And I'd do an electric choke myself) will be just fine.

IS this car a racer or just a mildly modified car?

OH, a larger carb doesn't move your power band higher into the rpm band, but allows it to breath upstairs in the rpm band. It may hurt down low if it is to much carb, which IMO, it is not. A to early wack of the throttle may not be so good though. High gear ratios fix most of that issue.
OH buck, a 750 will work fine up top the 383. It may be alittle more than it can normaly consume, but not a hinderance. (SP? ) It was a very typical thing to do for a 383. A swap from the small Carter (630 cfm's) to a larger Carter from a 440 (750 cfm's) was a normal "Hot Rod" thing when they were still on the new side.

I have a Carter Comp Series (Read replacement carb) 750 cfm on top of my 400. The bennifit to this AFB series carb over a DP is it at least has a secondary door that opens up with engine demand. I'd like a AVS up top myself. The air door being spring loaded is at least a little more tuneable than a weighted door.

My 400 is a stock dead on it's heels 1979 low compresion "Dog" of an engine. A smaller AFB on top did provided, IMO, a better throtle response and feel, but did lack a little on the top end.
Why not try just "setting up" the original Carter? I had a #'s matching 69 Bee with a 383 and auto that I ran the original (but tweaked) 625 AVS on and ran consistant [email protected].

It was a mile combo running less than a .480" lift, 9.9:1 comp, 346 heads, DP4B intake, headers, original convertor and 3.91:1 gears.

I tried a 750 that had been run on an NHRA record holding 383 and didn't run faster. But the car would have been faster with more stall, more gear, and better tires. Damn thing made power to 7000 but I was going through the traps at about 5300.

However, making it faster would have made it less streetable. As it was, I could drive it any were, and time, and get 15mpg driving 60 highway miles (one way) to the track.
thanks for that.

As far as I know its a stock rebuild. I baught the car and 2 months ago arrived here in australia. So i dont know what the previous owner had done. All i been told by him was, its a stock rebuild and running a "green cam"" which is just a notch above stock cam.

Hume performance told me the Street HP (4150 HP) 750cfm DP is all I would need as the Ultra HP and others would be waste of money unless I race the car all the time and need billet metering blocks and all those extra functions they offer to be able to tune up at every track etc etc.

Time out.

Exactly what are you planning on doing with this car? Drive? Race? How fast you think you want to go?
A plane old Holley Part number 4779, 750 double pumper will be fine on a 383 as long as your running 355 gears or lower.
I plan on using it for cruising, but when I stick my foot in it, i want the thing to go like a rocket and a DP will definately do that more so than a vacuum secondary.

Also need a manifold. Being a 383ci it makes power higher than a bigger ci motor, should i then look at dual planes to pick up some on the bottom or stick with a street dom intake single plane (which works well on big ci motors since the big cubes makes low power and single plane makes top end) ?
You'll get a shot of fuel for sure, but like I said, you better have enough motor (and gears) to take what you're gonna try to feed that motor. With a vacuum secondary carb tuned properly, the motor will only take what it can handle. Without knowing what is in this motor, I think you're setting yourself up for disappointment.

I've run both a single and dual plane on a 383. Unless you're running a 4 speed with gears, or an auto with a good stall and gears you should stick with the dual plane. It will help the bottom end.

Somehow I get the feeling no matter what we say here, you're gonna go get yourself a double pumper no matter what. But first, a story....

Once upon a time, there was a guy named Stan. Stan was a nice guy, but really knew nothing about making a car go fast. He had several cars and after spending money managed to slow them all down.

So Stan calls me one day asking about what cam to run in a new project. I asked what he was running (motor, intake, carb/s, exhaust, trans, etc). And after he told me I said run a stock (or split profile) cam. Well he didn't like what I told him, so he called a friend who knows a TON about building motors, and asked the same question. What cam? So my friend asks him for the same info I did, then gave him the same answer.

Ultimately Stan didn't like either answer, cause it wasn't what he wanted to here (only what he NEEDED to hear) So he puts the big bumpy cam in this thing and guess what. Yeah, it won't run. So like with cars before this one, he gets frustrated and gets rid of the car.

Moral of the story..... don't ask questions you don't want an answer to

good luck with your project
thanks for that. I ask questions cause im after opinions not because I "want"a DP. Reason I want to replace my 650cfm Holley is because 2 proffessional engine builders have said that a 750 DP would be best suited to the engine. Hence im running it by here to see what others think. The gears seem tall since in 4th gear your like 3000rpm at 60mph (or there abouts) assuming 3:55 or 3:95.
Well I question their recommendation without knowing any more about your motor than they/you do. At the very least I'd try to see what the cam is. You can at least measure lift without pulling anything more than a valve cover, rocker assembly, and pushrods. (you really need to check lift on the edge of the lifters (or slip a solid in for this if it is a hydraulic) and then multiply by the rocker ratio (1.5 if stock)

You won't know anything about duration without a degree wheel, but you might be able to make an educated guess at what the cam is by the lift (along shot). You're not gonna know anything about your compression ratio without pulling a head.

So like I said, I question these "pros" recommendation without knowing the cam (it's specs and whether it's been degreed and where it's centerline is), compression, what if anything has been done to the heads etc etc.

One last thing. I've been working on Mopars for over 30 years, building my own motors etc, and I've never heard of a "green" cam. Anyone else know what that is supposed to be?

I'm not trying to be harsh or come off like an ***. I'm just trying to look out for your interest
I ran double pumpers on everything Ive owned all most. Theres no problem with them when they are tuned right right. You just need to use the right sized carb for the application.

A 750 double pumper on top of a Performer RPM intake will be fine on a 383 with 355 gears.