Carb Choice for Stock 440?

[Isaiah Estrada]

Hey all! I asked this same question on FCBO, but I'd also like to get input from my good neighbors here on FBBO regarding my 440 build. Now, I know this is one of those kinds of questions that has a bazillion different answers… but I’m trying to be sensible, and not over carb a STREET driven 440 that will never see the race track or compete in any race.

For reference, my motor is a nearly bone stock 1968 440. Bottom end rotating assy is original. Has .030 pistons, stock spec cam, intake, heads etc. My car is going to be nothing but a street cruiser and highway driver. I wanted to keep my engine stock for reliability and drivability purposes.

I’ve done my own research on how carbs move air and how much of it they move! By using a CFM calculator (because science right? LOL) to get a rough idea of what “should” be used on my application. I got 650, which seemed pretty sensible once I put everything together. Again, I’ve got stock heads, intake, exhaust manifolds etc etc. Only thing that’s changed was that it’s been bored .030 over.

From what I understand, OVER carbing a car can really hurt its performance and just how well it behaves overall. Like, if I threw an 850 on this car - wouldn’t all my power now be at the top end and the car would be a dog at low RPM’s?

My understanding is that if I were to run a bigger carburetor on this particular setup, I’d have bad drivability due to the huge ports trying to flow more air than the 440 can produce. The port velocity will slow down when the size of the ports get big. A GREAT analogy i’ve heard compares these sizes to a small garden hose vs a a big tube… one trickles and the other sprays!

Am I on the right track with my thinking? I still have folks who think I should’ve went with a bigger carb, but again - this isn’t a performance car nor a racer. It’s a practical daily driver that I want to be reliable and have great drivability. Looking forward to your insight. Learning here has always been the best for me! The carb is an Edelbrock AVS 2 650 CFM (1906)

 

[Kimodc]

I am in a very similiar situation, except I still have stock intake and heads. I had a edelbrock 1406 (600cfm) for a short time that would stumble on hard acceleration. I switched to a Holley 3310 and think it runs great! Good power with no hiccups or starving for fuel, and very smooth and consistent acceleration.

 

[440 4 speed]

Hey all! I asked this same question on FCBO, but I'd also like to get input from my good neighbors here on FBBO regarding my 440 build. Now, I know this is one of those kinds of questions that has a bazillion different answers… but I’m trying to be sensible, and not over carb a STREET driven 440 that will never see the race track or compete in any race.

For reference, my motor is a nearly bone stock 1968 440. Bottom end rotating assy is original. Has .030 pistons, stock spec cam, intake, heads etc. My car is going to be nothing but a street cruiser and highway driver. I wanted to keep my engine stock for reliability and drivability purposes.

View attachment 1349559

I’ve done my own research on how carbs move air and how much of it they move! By using a CFM calculator (because science right? LOL) to get a rough idea of what “should” be used on my application. I got 650, which seemed pretty sensible once I put everything together. Again, I’ve got stock heads, intake, exhaust manifolds etc etc. Only thing that’s changed was that it’s been bored .030 over.

From what I understand, OVER carbing a car can really hurt its performance and just how well it behaves overall. Like, if I threw an 850 on this car - wouldn’t all my power now be at the top end and the car would be a dog at low RPM’s?

My understanding is that if I were to run a bigger carburetor on this particular setup, I’d have bad drivability due to the huge ports trying to flow more air than the 440 can produce. The port velocity will slow down when the size of the ports get big. A GREAT analogy i’ve heard compares these sizes to a small garden hose vs a a big tube… one trickles and the other sprays!

Am I on the right track with my thinking? I still have folks who think I should’ve went with a bigger carb, but again - this isn’t a performance car nor a racer. It’s a practical daily driver that I want to be reliable and have great drivability. Looking forward to your insight. Learning here has always been the best for me! The carb is an Edelbrock AVS 2 650 CFM (1906)

I think it should work well, but I’m not a mechanic. My experiences with original AVS carbs were very good.

 

[4speed68rt]

A Demon 650 or 700 cfm Street Demon, Vacuum secondary with an electric choke. A Carter 750 cfm AFB. Maybe an Edelbrock AVS 750. Stay away from the 850 cfm double pumpers. Too much carb. Smaller cfm will be more responsive.
Holley 750 would be ok too, but I like the 4 corner idle mixture adjustment on the Demon. Im not sure what Demon offers now that they are part of Holley.

 

[68BabyBlue]

I had a pretty unique experience comparing carbs on a stock, never rebuilt 440 in my '68 GTX. Owned the car in the 80s when it was equipped with stock Carter AVS, that my friend Bob had blue printed when he owned the car before me. It ran beautifully on the street, and turned low 14s consistently in the quarter mile. Fast forward thirty years, and the car comes back to me multiple owners later, now with a Holly Street Avenger, 770 cfm. Car ran flawlessly on the street, we both felt it was now stronger on the low end than with the Carter. Not willing to run a numbers matching 50 year old car down the track, so we never found out if it was faster in the quarter.

 

[turbine68rt]

I use a 1905 on my stock 440 except for Carlisle when the restored 4429 goes back on. I'm happy with the way the Eddy performs.

 

[GTX JOHN]

These cars with the 375 HP engine often can with a 750
carb from the factory. The drivability was great.. My 1967
440 Auto GTX came new with a Cal. emissions 625 which I replaced
with 750 AND both drivability and performance improved. It was
otherwise stock.

 

[440 4 speed]

These cars with the 375 HP engine often can with a 750
carb from the factory. The drivability was great.. My 1967
440 Auto GTX came new with a Cal. emissions 625 which I replaced
with 750 AND both drivability and performance improved. It was
otherwise stock.

I was mentioning AVS, because he has a 68.
I think your carb should be a 4327S. Our carb is a 4326S.

 

[66Satellite47]

I've always said a well tuned carb that is a little smaller can work very well. A 650 CFM can do just fine on a mild 440. You need to decide which style of carb you are familiar with. I'm a Holley guy because I understand how to work on and tune them. Over years I never got the hang of the Carter AFB or AVS or Thermo Quads. If you learn how each style works and what it takes to make them work go with that. Again as far as size goes 650 or 700 CFM is great for a mild 440.

 

[Isaiah Estrada]

Thanks to everyone for your input! I may go ahead and buy the separate tuning kit with different metering rods, springs and jets and see if we even need to play with any of it. Otherwise, good to have on the shelf.

 

[Montclaire]

I’m happy with an 800 cfm Edelbrock AVS2 on my 440. 915 heads with 484 cam. Took some time to get it right, but once they are dialed they are hard to beat on a street car.

You can certainly run a 440 with a smaller carb (440+6 ran on a single 2bbl until the outboards kicked in) but you will hit a wall when demand outpaces supply.

My secondaries hit like a hammer, and I just wouldn’t enjoy owning the car as much if they didn’t.

 

[Montclaire]

Thanks to everyone for your input! I may go ahead and buy the separate tuning kit with different metering rods, springs and jets and see if we even need to play with any of it. Otherwise, good to have on the shelf.

You need a strip kit 100%. Only way to go from a good running car to a great running car. They also sell a squirter kit. Pick up a vacuum gauge if you don’t have one - doesn’t need to be anything fancy.

 

[Kern Dog]

Nobody thought to mention the ThermoQuad?
Come on… it is an excellent street carburetor. Great throttle response. Better fuel economy than any other carburetor and those huge secondaries make some glorious sounds at WOT.

 

[AR67GTX]

I had an Edelbrock 800 AFB on my 67 stock 440 (actually a stock 68 440). I went through the carb to put it in the best shape I could, leaned it very slightly and it generally ran well. I found an original Carter 750 AFB for it and has it restored and put stock jetting in it except for one step richer secondary jets. It seems to run better with the Carter 750 - more responsive in part throttle driving And transition to full throttle. I think Mopar probably had the carburetor pretty much right for a stock motor.

 

[Stonehengeheel]

I have an Edelb 750 on my stock 440 and it runs great.

 

[WileERobby]

Nobody thought to mention the ThermoQuad?
Come on… it is an excellent street carburetor. Great throttle response. Better fuel economy than any other carburetor and those huge secondaries make some glorious sounds at WOT.

Could not agree more. Years ago, I ran a holley street dominator with a large TQ on it... one of the best running street 440's I've had.

 

[Geoff 2]

Yep, hard to beat the TQ. You get performance AND mileage!

 

[AR67GTX]

These cars with the 375 HP engine often can with a 750
carb from the factory. The drivability was great.. My 1967
440 Auto GTX came new with a Cal. emissions 625 which I replaced
with 750 AND both drivability and performance improved. It was
otherwise stock.

I second this. I have a restored, correct 750 AFB on my 67 GTX and it performs great. A nice, original 750 Carter AVS would be hard to beat for an essentially stock motor and they essentially run for ever - no leaking fuel from bowl or accelerator pump gaskets. No issues with warped metering plates and bowls. Stock choke setup works. Stock auto transmission linkage fits.

 

[68BabyBlue]

I second this. I have a restored, correct 750 AFB on my 67 GTX and it performs great. A nice, original 750 Carter AVS would be hard to beat for an essentially stock motor and they essentially run for ever - no leaking fuel from bowl or accelerator pump gaskets. No issues with warped metering plates and bowls. Stock choke setup works. Stock auto transmission linkage fits.

I have the original 4640 AVS in my ‘69 GTX and it works flawlessly.

 

[Don Frelier]

If you can add an O2 sensor then you can see exactly how your tuning is affecting the mixture.