Carburettor Opinions

Hi

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 use and would also buy a Holley. I've heard a lot of mixed reviews on the BG's.

thanks

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?

Takes a lot of motor to swallow what a DP has to offer. Make sure you aren't looking at to much carb.

I agree you might consider a 3310 Holley 750 vacuum

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 agree with 69 runner. A 750 is going to move your power band higher into the rpm band, and hurt your bottom end most likely. If you're running an auto with a pretty high stall convertor, or a 4 spd, it won't be too bad, but if you don't have the heads, cam, and means to use the 750, you're doing an overkill. That being said, I'm using a Demon 850 on a blown chevy sb 383, and it's working great. BUT.... blower, and a 3200 stall. Sure you want to put a 750 on a normally aspirated 383?

Hi

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 13.50@102.5.

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 ass. 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.

There ain't no such thing as a good double pumper for the street, unless you have one hell of a stout motor and proper gearing setup! If you use a fresh vac sec 4 bbl Holley, or a Edelbrock or Carter, you will have a much better running car! Double pumpers have no business on the street! ............. Later, John Lang:HappyNewYear:

no business on the street! ............ Oh yes they DO! LOL. However, just like you said, a stout engine and gearing to match really make it work alot better than if it was on a tank weight car and Hwy. gears. He he he

start by getting a vacuum gauge on it in gear, and making sure you've got a good signal. you should have probably 16-22" with this 'mild' cam in your engine. with that and a stock converter you dont need anything too big or exotic, you won't be happy with your engine guy's recommendations. not enough vacuum or too large a primary venturi, and forget about getting your idle mixture right, not to mention your transition, and main circuits. there are lots of ways to mask an oversized carb, they are all a pain in the ass-drilling primary plates, power valve sizing/timing, and jetting that is way off. try working with the carb you have now before you throw good money down the drain.
if your heart is set on a carb change, consider a holley street avenger. the first generation of these units had some issues, but holley has them worked out now. these carbs out of the box require very little adjustment, and this is good if you're not confident in your tuning abilities. holley even ships a dvd with their carbs now to help people set theirs up.
these are vacuum secondary, DUAL FEED carbs, not to be confused with DP's, with electric chokes-very easy to adjust. if this car is a cruiser, you will be very happy with the result. your mileage will slightly increase because the secondaries won't come crashing in the second you mash the throttle-they react with engine LOAD and DEMAND and will come in smoothly with the correct secondary spring.
holley has on their website, a "carb calculator" which chooses the best cfm for a particular application-check it out. and you should do some reading on how to properly size your carburetor, you'll see how easy it is to over-carb an engine and why.:grin:

Talk to Damon at this site. He,s the carb guru.http://www.diamondbackengines.com/forums/ also check out the air fuel section. will help in your decision,good reading especially the white papers

There ain't no such thing as a good double pumper for the street, unless you have one hell of a stout motor and proper gearing setup! If you use a fresh vac sec 4 bbl Holley, or a Edelbrock or Carter, you will have a much better running car! Double pumpers have no business on the street! ............. Later, John Lang:HappyNewYear:

does this mean i have to change my 1150 dominator to a 750 or only drive on the strip? lol

The gears seem tall since in 4th gear your like 3000rpm at 60mph (or there abouts) assuming 3:55 or 3:95.

Rear gear sounds more like 3.23.....all depends on the tire diameter....

My opinion is stay with the Carter...625 cfm.....in carb talk, bigger ain't always better.....I have a site for calculating what carb is best to use depending on max RPM.....I'll try and find it.

Unless your engine is built, I don't think the big carb is gonna help you

heres a link to the white pages http://www.fugly-racing.com/index.php?pid=2

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?
Cousin of the purple cam :grin:

I had the purple cam in my black 66 Charger back in the late 70's.....it lasted 3 months in there...took it back out....was not a good daily street driver....had wife & kids in car....they hated it...so I tossed it out.

Here is carb calculator site.....

http://www.4secondsflat.com/Carb_CFM_Calculator.html

Oh My God :drowning: plenty of opinions here...it's almost like 1977 again.

"THE" Purple cam?

ALL M.P. cams are "purple"

I had the purple cam in my black 66 Charger back in the late 70's.....it lasted 3 months in there...took it back out....was not a good daily street driver....had wife & kids in car....they hated it...so I tossed it out.

Here is carb calculator site.....

http://www.4secondsflat.com/Carb_CFM_Calculator.html

ditto on the 4secondsflat link-"big daddy" don is the man. i run his ignition in my gtx. ignition first, carburetion second. he specializes in mopar, and he campaigns a pretty sweet cuda. buy his tuning guide-best 10 bucks you'll ever spend. and to boot he's a super nice guy.

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.
Any 383 will handle this carb, even if its a 2V motor. In the day that was the most poplar swap made.

Any 383 will handle this carb, even if its a 2V motor. In the day that was the most poplar swap made.

LOL, damn skippy it was. On a daily driver with nice and mild manors, I'd do the smaller carb.

The larger carb would do very well with headers and a carb change etc....

I have a Carter 750 ontop of my otherwise stock 400, save the headers and MSD, it is bone stock. While not bad on the bottom end, the top end screams by compare. Though it's a choked smog engine, theres not alot of power to start with and not much to grow on unless it's rebuilt, ground up.

I like the added drivabilty of the smaller carb and will go back to it later.