Can’t decide which carburetor I need

[marshallfry01]

I've have researched about as much as I can and I can't decide exactly what carb I need for my 383. I'll give all the info I can on it... 69 charger, 383 that is .030 over, mild cam, eldelbrock performer RPM intake, stock HP manifolds connected to 2.5 inch TTI dual exhaust, 727 with a 2,500ish stall, 3.23 rear gears.

The car will mainly be street driven. I've narrowed it down to a Holley 750 DP but can't decide on mechanical secondaries or vacuum.

What would be the better pick? And why?

[cdr]

650 DP

[Kern Dog]

You do not want or need a double pumper for street use. You can use them but be prepared for the drawbacks.
They really dump in the fuel for WOT runs, drag racing, etc.
They also dump fuel each time you just bump the throttle a little bit. It really is a matter of too much of a good thing. Sometimes it is a good guideline to start with something that the factory used if your engine isn't too far from stock. The factory never used double pumper carburetors on Mopars sold for street use. If you look at the Carters they used, the accelerator pump shot is surprisingly weak yet the cars still ran strong. Yeah, they will run stronger with more fuel but there are limits and tradeoffs for that. The additional fuel will dirty the oil faster, increase cylinder wall wear and cut into the mileage a little.
I'll admit that they were conservative on carburetor tuning because the goals were not to obtain the most power but instead to run strong, long and be reliable.
I run a Holley vacuum secondary 750 on my 9.3 to 1 383, 280/474 MP cam, headers and Edelbrock Performer RPM intake.

[John_Kunkel]

They really dump in the fuel for WOT runs, drag racing, etc.
They also dump fuel each time you just bump the throttle a little bit.

Uh, not so...the rear pump isn't active until the secondary butterflies open and that doesn't happen until the primaries are about 1/3 of the way open. For normal cruising and even "spirited" driving the rear pump doesn't dump fuel.

[Kern Dog]

Sorry if I was wrong about that. I have only owned two Holley double pumpers. I forgot that the secondaries only open once the throttle is nearly halfway open. My mistake.

[b5blue]

  I use a Proform 750 vacuum secondary on my mostly stockish 440. I did up-size jets and it runs good. Here in Florida I found ditching the electric choke helpful.   

[496polara]

A holley 750 vacuum secondary will be more responsive with your setup than a dp IMO. One that has had the fuel curve set can be night and day over a box stock one.
Just be prepared to some tuning to get it right.Out of the box is rarely perfect.

[John_Kunkel]

IMO, throttle response is more a matter of carb size than the number of pumps.

I agree with cdr that a 650 or smaller would be appropriate for a mild 383...smaller throttle bores increase the air velocity at any throttle setting and, therefore, make more response with throttle changes.

[Dino]

Nothing made my car drive better than a Thermoquad. Crisp throttle response and hauled ass wide open. Pita to tune though. 

[John_Kunkel]

The TQ and QJ are examples of small primaries that yield excellent throttle response and toilet-sized secondaries for WOT performance.

[Kern Dog]

I'd agree to that. The Thermoquads do make a glorious sound under full throttle.
I've found that since my cars all sit awhile between driving them, the Holleys seem to retain the fuel in the bowls longer and start easier after sitting. I've had fuel in Thermoquads either evaporate or just slowly leak out over time and with the much milder accelerator pump system the Thermoquads use compared to Holley, cold starts after sitting awhile can take longer.

[Back N Black]

You do not want or need a double pumper for street use. You can use them but be prepared for the drawbacks.
They really dump in the fuel for WOT runs, drag racing, etc.
They also dump fuel each time you just bump the throttle a little bit. It really is a matter of too much of a good thing. Sometimes it is a good guideline to start with something that the factory used if your engine isn't too far from stock. The factory never used double pumper carburetors on Mopars sold for street use. If you look at the Carters they used, the accelerator pump shot is surprisingly weak yet the cars still ran strong. Yeah, they will run stronger with more fuel but there are limits and tradeoffs for that. The additional fuel will dirty the oil faster, increase cylinder wall wear and cut into the mileage a little.
I'll admit that they were conservative on carburetor tuning because the goals were not to obtain the most power but instead to run strong, long and be reliable.
I run a Holley vacuum secondary 750 on my 9.3 to 1 383, 280/474 MP cam, headers and Edelbrock Performer RPM intake.

I was running a 770 Holley with vacuum secondaries and changed it out for a Proform 850 double pumper. Night and day difference. The 850 really woke the motor up. Runs great for the pass 5 years, no issues.

[Kern Dog]

For the pass five years? The overpass or underpass....?
It may run great for awhile but you are likely pumping more fuel into the engine than it needs. This always leads to increased engine wear due to the unburned gas washing oil off the cylinder walls, which accelerates wear and increases oil consumption.
If you're okay with that....feel free to stick with it.
I've seen guys with plugged vacuum advance cannisters, exhaust manifolds on cars with big cams, high rise intakes on stock engines, all sorts of mis-matched combinations.

[b5blue]

Here, read this to help understand that ANY changes to the engine require changes to the carburetor. Variables are so many you'll find any opinion you want!
https://www.tccoa.com/d2/members/392bird/tuning.htm

[Back N Black]

For the pass five years? The overpass or underpass....?
It may run great for awhile but you are likely pumping more fuel into the engine than it needs. This always leads to increased engine wear due to the unburned gas washing oil off the cylinder walls, which accelerates wear and increases oil consumption.
If you're okay with that....feel free to stick with it.
I've seen guys with plugged vacuum advance cannisters, exhaust manifolds on cars with big cams, high rise intakes on stock engines, all sorts of mis-matched combinations.
[/quote

For the pass five years? The overpass or underpass....? Overpass underpass what the fuck are you talking about?
I had a 770, the car would run rough at idle, did many adjustments, engine rocking back and forth at idle. New carb fire it up smooth, crisp throttle, 1 pump start up. pulled the plugs today actually, its the best they ever been. And its seat of the pants improvement WRT power. I have a 284 comp cam, Eddy RPM heads, Eddy high rise intake. makes 550 hp and 560 torque.

[Kern Dog]

I made a joke at the spelling error, man.
PASS 5 years?
No, that should be Past 5 years.
I guess sarcasm can be hard for some to detect.

[Back N Black]

Sometimes its hard to detect sarcasm on the inter web, its all good.

[John_Kunkel]

I'd agree to that. The Thermoquads do make a glorious sound under full throttle.
I've found that since my cars all sit awhile between driving them, the Holleys seem to retain the fuel in the bowls longer and start easier after sitting. I've had fuel in Thermoquads either evaporate or just slowly leak out over time and with the much milder accelerator pump system the Thermoquads use compared to Holley, cold starts after sitting awhile can take longer.

The only TQ I've ever run was on a bone stock '72 Charger with a 400 Magnum. Even as a daily driver it was reluctant to start right up after sitting overnight. A friend who was a dealer tech said that the TQ is very sensitive to choke position, the choke butterfly has to be very firmly closed on cold startup or it'll require excessive pumping and cranking.

He tweaked the choke stove, fiddled with the metering rod cross bar and, after that, it always started up right away when cold. Lesson learned.

[Kern Dog]

Dang John....you forced me to agree with you twice!
Yes...I had a Thermoquad on a 360 in a Dart Sport that was rebuilt. It was very hard starting until I rummaged through my stash and found a proper choke assembly for it. With that in place, there were mornings that it would start without even bumping the throttle at all. Fast idle at first, gradual descent to standard curb idle speed once it warmed up.
When tuned right, they are fantastic.

[Captain D]

I once had a Holley double-pump carb on my 383. Although Holley's are reputable carbs no doubt, the dang thing left me stranded based on the responses already mentioned in this thread (it was just too much = flooding, etc.). I've heard that the Edelbrock AS2 650 carburetors (with electric choke) are very nice and all that you'll need. They're available on Summit Racing.   

[b5blue]

They all have to be tuned to work and yes not too big to be tuned.

[69wannabe]

I ran vacuum secondary carbs for years on my different hot rods and older vehicles. I had a vacuum secondary 750 holley on my 440 then a buddy of mine had a 750 DP holley he wanted me to rebuild for him. I rebuilt the double pumper and put it on my 440 to set the float levels and make sure it ran good. It ran great actually on my 440. Much more responsive than the 750 vacuum secondary that I had normally running on the engine. I wound up trading him out of the 750 DP carb so I could keep it on my car. Probably the best carb that has ever been on my car performance and drivability wise. When I went to the 493 ci I went up to an 850 DP holley carb. This is also a good carb and is responsive and has good drivibility as well. Had to do some tuning as with every carburetor but I have had it on the car for over 10 years and haven't done anything to it after I get it tuned in except check the idle mixture screws every now and then. Comes down to preference I guess but I'll take a double pumper over a vacuum secondary carb any day. On a healthy 383 I still think a 650 double pumper is a good pick. I have seen several 383's run good with a 750 and it is doable but maybe just a slight bit big for it.

[marshallfry01]

Well I ended up going with the Holley 750 vacuum secondaries with electric choke. 4160 series. I'm waiting on a few more things to come in so I can fire it up and do the break in. Can't wait!

[b5blue]

I ended up installing a manual choke. Florida is so warm it was dumping too much fuel too long. 

[marshallfry01]

I ended up installing a manual choke. Florida is so warm it was dumping too much fuel too long. 

What part of Florida are you in? I fly into Destin and PCB a lot for work.

I'm in Arkansas...I may have the same issue with the choke. Our weather here is crazy. Yesterday it was 80. Today was 50. Tomorrow is supposed to be mid 60s. I might need the choke more than you.