What Carb for 383 R/T

[Challenger_7]

Hi Guys
One of my 71 Challengers is an all original R/T Auto, 383 magnum engine, but I believe that over the years before I owned it, the carb was changed, and a smaller one was fitted to it.
The car performs extremely well upto 3000 rpm, then sort of falls short of power.
Question is, after I thoroghly investigate all aspects that might lead to such a state, if a new carb is needed, what cfm should it be?
From your experience, what is the ideal carb to fit on it, if different from what originally came on this engine?

Attached is a photo of the car.

Thanks

[Killer_Mopar]

I had a 750 Holley on my mild 383 and it worked great, so that is my recommendation.

[Challenger_7]

Thanks Killer. Any idea what was originally fitted from the factory, how many cfm?

[nivvy]

Well Barry Grant from Demon carb says take cubic inches(383) X Max Rpm (5500?) divided by 3456 equals desired carb....

383X5500='s 2106500 / 3456 ='s 609.51 so I'd say a 650 is good according to BG.......

[MEK-Dangerfield]

I'm guessing your car had a 600 from the factory, maybe 650 tops, but I doubt that. Has the engine been built up any? Bigger cam, headers, and such? If it is still stock, I wouldn't go more than 700, or 750 tops.


  Mike

[Challenger_7]

Thanks a bunch Stroker. This sure helps a lot
I have been trying to get an answer to my 350 ss Camaro 72, at the Camaroforum, but have not had any good replies. If this formula really works, then it is a great tool to use.
One thing though, would the high lift cams and the longer duration they remain open etc make a difference or not really??

Hello Mike, its been a while
What do you think of Stroker's reply?
My engine is still stock, untouched.

[Killer_Mopar]

Factory 383s usually came with 600s if I remember correctly. The BG formula seems quite a bit off....but then again BG carbs are rated different then most other carbs. If that calculation results are for a 610 BG carb, then that is probably equivalent to a 700+ Holley. Also, a bigger cam will make a difference because the more air the engine sees, the more gas it will need too.

[Chryco Psycho]

the formula simply doesn`t work in the real world , mainly because the carbs tend to be over rated , 750 is wherer i would start on a 383