Help with Carburetor selection

[1969 beep beep]

Hi everyone,

I am in the market for a new Holley double pumper. I can't decide between a 750 or 850. Here is my combo that I am currently building:

Street car only
69 RR 4100lbs with driver with a/c
3:91 gear which may change to a 3:55 or 3:73 in the future
4 speed
499 low deck (4.150 stroke)
holley dominator intake
1 7/8 TTi headers
2 1/2 TTi exhaust
ported stealth heads
solid flat tappet @50- 250 intake 256 exhaust 110 lobe at 560 lift


Any recommendations would be great. I am also looking at the Ultra Double pumper.

I ran the above combo with a smaller solid roller cam @50- 236 intake and 243 exhaust 112 lobe at 550 lift, an Edlebrock DP4B intake and Edelbrock 800 avs. The engine ran great but I felt the power was suffering down low especially being a torque monster.

 

[747mopar]

A cam like that will like some rpms plus 499 cubes............ I say 850cfm.

 

[texas69bee]

You could google carb calculator and enter the parameters of your motor. This will give you a good starting point. Some say the result will under carb your car. For street I'd say the 750.

 

[ctreser]

I recently put a Edelbrock RPM with a AED 750 HP-HO which came with 77/85 jets, 4.5 power valve, .031 squirters primary and secondary on my 440 with similar build but automatic. I could not be happier. Instant response with absolutely no bog.

 

[Meep-Meep]

Street car only go with the 750.

 

[TetanusShot]

Fuel Injection

 

[1969 beep beep]

Thanks guys for the responses. What should I use for volumetric efficiency % ?

 

[Canyon707]

try between 95 and 1.10

 

[lewtot184]

volumetric efficiency at peak torque and peak horsepower will probably be different. don't use those stupid *** cfm calculators. an 850 won't feed 500 cubes. a 950hp is just a 750 with a contoured body and 850 throttle blades. a 1000hp is an 850 with a contoured body. niether will flow what they're rated at. a 750 is a 340/383 carb. all this cfm stuff is just marketing garbage.

 

[383man]

With that combo and 499 cubes I would run the 850 for sure. I run this 850 DP on my 493 which is close to your build as I am at 10.6 comp and use the basic EZ heads. I also use a solid flat tappet thats a little bigger then yours as its 264 & 270 @ .050 with .585 and .592 lift. I know I could go faster wih a larger carb but this 850 is a nice carb for the street and strip as it works great for me. To me with the cubes and eng you have I would go with atleast the 850. I ran a 750 DP on my 383 and it worked very good on it and we do run a 750 with the airhorn cut down on my sons 400 and it works nice on his 400. But you have 100 more cubes and more cam and heads as your combo could easily handle an 850. Good luck what ever you decide on. Ron

 

[1969 beep beep]

Thanks Ron for the great feedback.