I have a 440 in my 68 Dodge Coronet and it has a Edelbrock 1405 that handles 600 CFM, I was told I can go with a dif size carb to get more HP out of the car, How true is that.

 

raycan -

Depends on what's been done to the 440. Holley has a cfm calculator on their web site that will give you optimal cfm based on engine displacement and max rpm.

For a bone stock 440, the 600 isn't that far off. The more that's been done to it, (manifold, hotter cam, headers and wide exhaust, as well as balancing and blueprinting to allow higher rpm) and you're in the 800/850 range.

Just remember that max cfm requirements implies at max rpm, you while you might get a little more power at top end, you might loose some responsiveness in the lower range.

Other factors include primary size and tweaking and that might affect gas mileage, either better or worse.

Archer

 

I would install no less than a 750 on any 440 , if you go away from the Carter Eddy style you feel even more difference . My preference is Proform , by far the most tunable carb for the price After 72 even the 340/360 had an 800 cfm TQ

 

CP -

CFM is only part of the picture. The TQs (which I kinda liked on a small block), had relatively tiny primaries and huge secondaries. "Most of the time" the transition worked. There's a little bit of difference when compared to a square bore (Holley) carb.

Oddly enough the factory Holley on 440s was about 600 cfm, vac secondary.

Too many people think that bigger is better, but that's not always the case. Most cars that see more street time than race time do better being slightly under carbed than over, IMHO anyway, due to better throttle response and "maybe" maieage.

Again, since we don't know what was done to the engine (if anything), it's really hard to make a call.

Archer

 

I agree without knowing the engine it is hard to make a good call , But the 440 AVS is bigger then the 383 version & was closer to 700 cfm , True bigger is not always better but I have yet to see even a bone stock 440 not like a 750 square bore .

 

CP -

Not saying a 750 Vac would be a bad choice, it's probably the best first pass carbs going for a mild street 440 (that's what I started with). Just that I've been surprised by more than one 440 sporting a 600 DP.

Think we're on the same page.

Archer

 

Throwing CFM numbers around has always bothered me. The older 413/426's had much smaller carbs than a 650.

AND claiming that an 800-850 TQ is sized right for a 340 leaves out an important point --- the secondary air door makes this carb ACT as a vacuum secondary, and nobody has ever proved to me that a 340/ TQ combo EVER opened up all the way to full flow.

There is no reason a mild 440 should not run good with a properly set up 600, and depending on LOTS of things

heads/ combustion chambers/ headers/ manifolds/ cam and on and on, a 750 DP might well be too much, although a 750 vacuum sec. could do pretty well.

Also, Carter/ Holley 4bbl flow ratings are (were) not derived the same way!!!! Holley rates theirs in "dry air" and Carter (used to) rate them "wet." So a Carter carb rated at XXX flows more than a Holley rated at the same XXX figures. I have no idea how Edelbrock currently rates them.

And don't forget that a 2BBL Holley is NOT rated at the same vacuum as a 4bbl. Holley 4bbls are traditionally rated at 1.5" drop across the carb, where Holley 2bbls are rated at 3" vacuum. There is a formula to equalize them for comparison.

 

true true bigger is not always better.

i always seen better options with spread bore and adjustable sec. of some sort vac or air valve .
my eddy 650 spread bore is nice would work great on that 440.
but of course your combo is always important.

 

The numbers, in my opinion, are marketing gimmicks at best. Holley to Carter to Edelbrock..is like comparing apples to grapes to oranges.

As 440roadrunner said, bigger carbs can and have been used with great success on smaller motors especially with vac secondaries. But they all need to be set up correctly. I have used many Holley 750 with vac secondaries on small 302s and 318s and 360s without issues. (Yes, I said 302s sorry... I don't discriminate ) Simply change the stock secondaries to an adjustable block and change the diaphragm spring for vacuum and you can get your air fuel for high rpm while tuning your idle and low speed circuit decent.

If the carb is THE restriction in your motor then changing to a bigger one will yield more HP all things equal. If it is not THE restriction then no gain will be realized at all. Almost all OE stuff runs fat with fuel. Its just safer for the big three to keep the motor happy.

When I do the math for a OE stock 440 with a 5000 rpm shift point it yields 639 cfm needed considering normal ( stock efficiency). This is just a guide line.

For a stock 440 I would recommend a Eddy 650 for excellent off idle acceleration and easy tuning with good OE type reliability.

If you add headers and intake then I would start with a Holley 750 vac sec minimum for the street. Get the spring kit and quick change top.

 

I agree that a stock 360 would rarely if ever fully opens the carb . The Math doesn't work either though having spent a lot of time on the dyno & at the track with numerous carbs 2x the CI is closer than the VE formula Wether that has to do with the carb not really flowing the CFM it is rated for or just the vacuum under the carb changing the real air flow is up to debate , for example 2 bbls are rated with 3" of vacuum while 4 bbls are rated @1.5" so the small outboard 6 pack carb is rated at 500 CFM while the small Holley avenger 570 4 bbl is not rated with much more flow so what happens when you engine is making .5" or less @ WOT . My experience on my Race car was similar it had a well built 440 shifting at 7000 rpm , I started out with an 850 double pump it ran in the low 12s , swapped to a 950 no way past the math recommendation but it was fater so I swapped intakes & went to 1050 dominator , the car dropped into the 11.7s & was more responsive & drivable to boot , I drove it to the track as I did nto have a trailer , 2 hrs each way . Even the mild 440 gained with the 6 pack over a 4 bbl even if those secondaries never opened fully either !
The other thing to keep in mind is big carbs really were not developed until the late 60s, in the 50 & early 60s all they had was smaller carbs , so they used multiple carb set ups , 3 or 4 2 bbls , 2 small 4 bbls etc , I even have a 950 3 bbl carb , it was before the dominator & made on oval secondary to increase air flow through the std 4150 body , it works great !
I stand by my original comment that an 750 is the smallest carb I would use even on a stock 440 , it works in my world

 

my brother ran a 850 quad-jet from his 500 ci caddy motor, on his 440
that was replacing a 650 double pumper and man it ran great, snappy throttle response and massive power gains.
the motor ran great with the 650 would bury the 150 speed o at 2/3 throttle and have no more red line left
with the 850 it just did it faster with 1/2 throttle left. and when that big air valve open up what a roar.

 

with the eddle 650 spread bore on my 318, it runs great might not be using all of it but it's working. and in the future if i ever move up to a 360 or larger i can swap the carb to it we, never throw anything out we just store it until needed and man we got a ***** load of carbs.

 

Auto or stick? What rear gears? Manual with 3.54:1 or steeper...drop a Holley 750 DP on it and prepare to be amazed. If it's an auto with decent gears I'd try out a Holley 650 DP.