Is 850 cfm too much for warmed over 440?

[6PKRTSE]

An 850 is perfect for a 440. I run a 850 on my bone stock 440 New Yorker with a little super power shot of Nitrous and this cars scoots for a 6200 lb tank. It just takes some jetting, secondary cam, and a/f adjusting to get it dialed in.

 

[MerlinsMopars]

I stuck a 750brawler on my 340 which was all new everything. Ran fine for the first few rides and then was bogging and I tore the front bowl off to find the float had a pin hole in it. Was full of gas. Replaced the float and that carb is a good 1. Had an 850 dbl pump on my 440 with the .509 and was a great match. It was 4 sp with 3.55s. I blew that rear and went to 3.23s and actually liked those better. I'd stay with the 850 and do some tuning. Could have something stuck in it. Make sure its clean and I always throw a 50cc pump in the back. Don't drop more than 2 sizes jets at a time and stay consistant with the rear jets also. Good luck with it. Thats a beautiful car. I had to get the dog dishes when I checked out your garage.

 

[djais1801]

I stuck a 750brawler on my 340 which was all new everything. Ran fine for the first few rides and then was bogging and I tore the front bowl off to find the float had a pin hole in it. Was full of gas. Replaced the float and that carb is a good 1. Had an 850 dbl pump on my 440 with the .509 and was a great match. It was 4 sp with 3.55s. I blew that rear and went to 3.23s and actually liked those better. I'd stay with the 850 and do some tuning. Could have something stuck in it. Make sure its clean and I always throw a 50cc pump in the back. Don't drop more than 2 sizes jets at a time and stay consistant with the rear jets also. Good luck with it. Thats a beautiful car. I had to get the dog dishes when I checked out your garage.

replaced the needle and seat and was okay for about 2 days..now it is bogged down and won't restart unless i keep pedal to the floor and there's no fuel in the front bowl window.

 

[MerlinsMopars]

replaced the needle and seat and was okay for about 2 days..now it is bogged down and won't restart unless i keep pedal to the floor and there's no fuel in the front bowl window.

Needle might be stuck and not allowing bowl to fill. Try unscrewing the float adjustment and check the needle isnt stuck.

 

[REM]

IMO with a 440 you can't go wrong with a 750 CFM

 

[fasjac]

replaced the needle and seat and was okay for about 2 days..now it is bogged down and won't restart unless i keep pedal to the floor and there's no fuel in the front bowl window.

After you get it started, does it idle/run ok?

 

[volunteer]

My '68 440 (in '74 Challenger) was pretty much factory Magnum specs. - including cam, heads and exhaust manifolds. I started with the #3310-1 (Vac.) Holley on top of Torker. This was a very good combo - in spite of annoying electric choke. It pulled in first gear (323 rears) to 6200 and then shift and 5800 in second.
After a couple years I installed the bigger T.Q. on top of Performer intake. This setup used factory well-type choke so better starting - cold or warm.
Performance felt about the same but one benefit of the T.Q. is much easier tuning. (I have the strip kit). The Holley was good and since engineered in the mid-sixties for the G.M. 396, it was already internally calibrated for a bigger cam than Mopar's Magnum, S.C., TNT version. I found it necessary to decrease main jet size from (I think it was 72 to 69), and also an accel. pump adjust and slightly lower floats. Sure, it ran okay 'out of the box', but a bit rich on fuel. With the 15 inches of vacuum, the T.Q. was already dialed near perfect.
Note also that the original (1974 booklet) Carter T.Q. specs. claim that the two versions of Mopar's (OEM) units were rated (by Mopar) as 800 and 850 cfm. The venturi areas were 10.17 and 10.92 - respectively. When sold as (very rare) Competition Series versions, Carter rated them as 850 and 1000 cfm - - but also with the corresponding venturi sizes as Mopar's units. So, obviously a lot of performance and air flow potential. Pretty sure I already posted something about this so forgive my annoyance.

 

[djais1801]

After you get it started, does it idle/run ok?

it starts but at jump off idle its spotty and then opens up at mid/high range...just when you come to a light/ corner to turn it wants to stall

 

[fasjac]

Almost sounds that not getting enough fuel at times. Everyone here has talked about it all. I just wonder if your getting a restriction somehow. All you did was change the needle and seat right? I’d have to go back to that first. Taking an easy turn and it want die is like the float got hung up or not enough fuel. I’m not an expert by no means. If it were mine I’d go back to the float and needle and seat. Maybe something foreign is floating around in the bowl??
A rebuild isn’t that difficult either. Hang in there dj.

 

[fasjac]

And if it’s an electric pump, you may have an intermittent issue. You could also check the fuel delivery. Just thinking out loud.

 

[Geo]

With a little work and tuning it should work fine. Not real fond of the torker 2 intakes

 

[Ted70challenger]

I got a 1150 dominator on a 440 it’s got Indy heads and intake and about.530” cam , but it does stumble when suddenly floored .
I haven’t worked it out . . 850 your fine .

 

[Chryco Psycho]

It is also possible that the fuel bowl is overfull so you can't see the fuel line in the window .
Keep in mind Mopar used the 850 CFM Thermoquad on all 440s from 71 - 78 , why would you use anything smaller ?

 

[djais1801]

so update...I changed the carb to a edelbrock AVS2 800 w electric choke. still had some issues but i believe it was my fuel pump...the pump crapped out on me and after i swapped it out all the issues disappeared. i pulled the push rod and it was not worn down.

 

[Cojohnso]

Use what you like.. but this formula has been around for a while. It may run well with an 850 , probably better with a 750/780 .. and although you didn't ask, a 3" exhaust is over kill on that engine. IMHO


How to calculate Carburetor CFM
The formula for calculating how much CFM (cubic feet per minute) your engine requires is: CFM = Cubic Inches x RPM x Volumetric Efficiency ÷ 3456.

Any ordinary stock engine will have a volumetric efficiency of about 80%. Most rebuilt street engines with average bolt-ons have a volumetric efficiency of about 85%, while race engines can range from 95% up to 110%.

Example: Using a 355 CID engine x 5,500 max rpm = 1,952,500
Take 1,952,500 x .85 = 1,659,625
Then 1,659,625 ÷ 3456 = 480 CFM


Even with about a 10% cushion, a 500 CFM carburetor will handle this engine great. If you try this formula yourself, be honest with how much rpm the engine will see. You’d be better off with a carb smaller than needed rather than something oversized that can lead to poor drivability and performance.

I wonder about alternative fuel? Like carb metered for E-85? Or methanol? It wouldn't surprise me if close to same as gas? Motor's on alcohol typically needs more fuel. Not more air. But these motors are typically higher compression or high boost thus higher volumetric efficiency. But I could be wrong?

 

[fasjac]

I wonder about alternative fuel? Like carb metered for E-85? Or methanol? It wouldn't surprise me if close to same as gas? Motor's on alcohol typically needs more fuel. Not more air. But these motors are typically higher compression or high boost thus higher volumetric efficiency. But I could be wrong?

Here’s a Dart 500 stroker, toilet bowl on alcohol and a real sticky track.

 

[Chryco Psycho]

A few downside to alcohol , 1st you need 35% more fuel to make the same power , second you cannot let it sit , it will jell up & clog fuel lines so you need to purge the system with gas everytime you park it for more than a week or so , 3rd it is very corrosive .