383 Carb Choice

[Hankohop]

Hey everyone, it's winter and I know most of us are going stir crazy. I've been rolling around the idea of a new carb for my Charger. I currently have a mild power built 383. It was my dads car when he was a teenager and he popped an 850 double pumper and a cam in it. Today, I still jave the same cam and carb on there. It runs and runs well but down low its a little rough to try and tune. Thats also probably due to the single plane intake I tossed on there.
Anyway, in my research I'm finding that there are a ton of mixed opinions out there for what carb is best for a 383. Some swear by the 850, others a 750 and even 650s. The double pumper seems to be the go to choice for 4 speed cars, which is what ive got; but there are plenty who stand by edelbrock or thermoquad.
I know it ultimately comes down to the intended use of the car but I figured that anyone who's looking for a general tech discussion to exercise their brain could weigh in on what carb they like the best for 383's. It's all a learning experience so any input is welcome!

 

[Don Frelier]

You may just have too much cam.
I ran a weiand dual plane with a Carter Competition series 625 cfm on mine for years.
With the .455 cam it was about perfect.
Before that I ran the original 500 cfm AFB and the low end was slightly better.
Small primarys seemed to work well on mine.

 

[Cranky]

The 850 might be a tab big but a 750 DP worked pretty well on a mild build 383 and 3.91's that I had back in the 70's. Can you post what all you have in the car like cam size, heads, headers, rear gear etc etc

 

[The Rebel]

My Charger came with a purple cam, Edlebrock performer 383 intake & Edlebrock 750cfm. The 750 is probably your best bet.

https://www.edelbrock.com/performer...ith-electric-choke-in-satin-non-egr-1411.html

 

[Hankohop]

Not positive on the cam grind (which is not good for this specific conversation or really ever.) But the engine is bored .030 over, I have 516 heads that have been milled, ported polished and fitted with 2.14 intake valves and 1.80 exhaust valves. Out back I'll be setting the car up with 3.55 gears. I have long tube headers with the od of the runners at 2 inches. The exhaust is a simple 2.5 inch set up with glass packs. Not knowing my exact can grind off hand does change the conversation a bit but really, I'm just looking for what other guys have out there in the world.

 

[69roadr]

I have a 750 Holley with 391 gears if that helps runs like a bat out of hell

 

[65-440]

.030 over 383, 9.44:1 compression. .... Holley 770 with 3.23 gears. I've been wanting to go down 100cfm and see how it reacts. Runs great as it is, but I am curious!

 

[Hankohop]

.030 over 383, 9.44:1 compression. .... Holley 770 with 3.23 gears. I've been wanting to go down 100cfm and see how it reacts. Runs great as it is, but I am curious!

This is where I think most of us can agree that having access to a stockpile of parts to monkey around with and find the answers would make life amazing haha

 

[65-440]

I went down 100cfm on my 340 dart and the difference was very noticeable. Much better starting both cold and hot, very crisp low rpm throttle response. However I did lose some higher rpm pull, its very noticeable. Around town it's great, but I had to relearn my shift points when driving hard. Doesn't wind out like it used to....

 

[furryfrog]

Not positive on the cam grind (which is not good for this specific conversation or really ever.) But the engine is bored .030 over, I have 516 heads that have been milled, ported polished and fitted with 2.14 intake valves and 1.80 exhaust valves. Out back I'll be setting the car up with 3.55 gears. I have long tube headers with the od of the runners at 2 inches. The exhaust is a simple 2.5 inch set up with glass packs. Not knowing my exact can grind off hand does change the conversation a bit but really, I'm just looking for what other guys have out there in the world.

What rpm is your idle? What's the vacume? Is it idle that's just rough or is slow speed drivability? What kind of converter?

 

[Hankohop]

It's a stick so no converter, I've been trying to hang my idle around 800rpm. Have yet to put a vacuum gauge on it but I can shoot to do so tomorrow and get back to you!

 

[Cranky]

Where the cam is 'set' can have a big difference on how an engine runs too. It's a pita but putting a degree wheel on it can tell you a lot. After reading a cam card and conversing with a buddy who knows way more than I do about cams, I usually advanced them a few degrees for street use and they usually ran purty darn good.

 

[furryfrog]

It's a stick so no converter, I've been trying to hang my idle around 800rpm. Have yet to put a vacuum gauge on it but I can shoot to do so tomorrow and get back to you!

Idling at 800rpm and a single plane could be an issue. What single plane? If it's a holley street dominator you should be ok. Other members will have more experience on this. I would guess a 750 would be a good fit, (assuming you want a holley DP) but a 750 could be just as tricky to tune down low. When does your power band drop off rpm wise. I think you should put the other intake back on, or try a dual plane, or a street dominator. You said it ran well before you swapped intakes? I think you answered your own question in your question lol. If it's all about learning, buy a hotter cam to suit the single plane and the 850 you already have. Cams are cheaper than carbs.

 

[PurpleBeeper]

Well, for my 2-cents...
a. put a dual plane intake back on it for sure
b. I would ballpark your carburetor at 650-750 cfm with the brand of your choice. Match "square bore" or "spread bore" vs. the intake you have. Personally, I got better results with a 750cfm vacuum secondary vs. a 650cfm double pumper, even with a 4-speed. The double pumpers CHUG gasoline.
c. I would suggest a 750 Holley vacuum secondary & start out just about "out of the box" and tune from there as needed.

Personally, I prefer Holley, but I have had VERY good luck with Edelbrock & Thermoquad carburetors too.

 

[beanhead]

Even if you're not sure of the cam, if it's bigger than stock a 750 will be fine size-wise. If you've got a little extra coin you could go for a carb with annular boosters, this will help your low and response a little more as well.

 

[Dajkzo]

For comparison, my car currently has a 383 with 9-1 and a little too much cam duration (10" vacuum). Headers and a Holley SD intake with a 650 Edelbrock carb. The low end and throttle response is OK. This is how I purchased the car. Given a choice, I would opt for a good Holley style 750 DP with mechanical secondaries in a 4-speed config. An 850 is great at WOT. And as much as we would like to, you just can't drive like that on the street. (well most of the time heheheh)
Get out your vacuum gauge and timing light, set your idle and base timing and then tweak the idle mixture to get the best vacuum reading. Test drive and tell us what the results are. You can spend time with tuning (jets, air bleed, etc), on that 850 but in the end a 750 is going to work better.

As far as brand goes, the past few years I've been happy with AED. Their tech support is decent.

 

[Larrry B.]

For a stock / mild 383 build, the best overall driving experience I've had to date on the street was with an Edelbrock RPM performer dual plane intake with a 670 Holley Avenger.

You could probably go to 750 and still have fun, anything more and you'll need to do more mods to get your moneys worth.

 

[JackpotJim]

I have a mild 383, headers, Performer RPM, 727, 3.73 gear in my 66 coronet. I put a 770 cfm Quick Fuel Holley on mine. Like the adjustability of the Quick Fuel.

 

[Jcharger]

With a 4 speed and 323 or higher numerical ratio, I would go with a 650 or 750 mechanical secondary with annular boosters. The decision would depend on how high up you plan on pushing the RPM. If it is 5000-5500 or less, then I would use the 650. Tuning for throttle response will be simpler and that is where most driving happens. I know vacuum secondaries are supposed to work better, but with a manual, my car liked a big pump shot. If you are racing, then you may need something different.

 

[idrivemopar]

Thermoquads are nice, that is, if you can find one that is in good condition without significant wear on the throttle rods, most are missing the coating and therefore cause issues with vacuum leakage around the throttle rods. But, if you can find one, they are nice, because of the vacuum secondary's, they are good on fuel until you put your foot down, and nothing sounds like a thermoquad when the secondary's open up! Also, once you tune them in, they never change. I do know they perform much better with ethanol free fuel and evaporate fuel faster than most carbs when they sit, they do have a lot of open venting. I have tried several different ones until I got one that worked properly, so not trying to discourage you if that is the direction you want to go, just be aware of the pitfalls of resurrecting a thermoquad, it can be a challenge.