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Proper size carb

3sloppydogs

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so I put togther a mild 440. Stock bore, edlebrock rpm heads and manifold, lunati cam.
According to the math my carb should be 649CFM. Now that seems a little small to me but thats what the numbers say. I have an old 1412 edlebrock, 800CFM, I could install that but I think I won't be happy because the lower carb signal with that size carb will be constant idle issue and tuning problems.
So the next choices are 670 street avenger or a 750 avs or just go with the 650 avs. Thoughts on this?
I'm sure this has been covered ad nauseum, just seeing what you guys did
 
so I put togther a mild 440. Stock bore, edlebrock rpm heads and manifold, lunati cam.
According to the math my carb should be 649CFM. Now that seems a little small to me but thats what the numbers say. I have an old 1412 edlebrock, 800CFM, I could install that but I think I won't be happy because the lower carb signal with that size carb will be constant idle issue and tuning problems.
So the next choices are 670 street avenger or a 750 avs or just go with the 650 avs. Thoughts on this?
I'm sure this has been covered ad nauseum, just seeing what you guys did
You didn't give us the cam specs or compression ratio or transmission/ rear end but, I would use 800/850 cfm.
Mike
 
With a 650 it'll probably have really good low rpm / off idle characteristics for sure, but you'd definitely be losing a bunch on the top end....holley street avenger 770 or edelbrock 800 AVS2 would be better choices in my opinion
 
I think I read it here that the stock round air cleaner is only good for letting around 600 cfm through , if your running that its another thing to think about
 
We need more to go on but a 750 would be my choice as far as cfm goes.
 
What are the plans for the car ? Mostly street ? Track sometimes ? Track only ?
Everybody has different thoughts depending on the use of the car.
You are correct with the calculation of 649 for a street driven car for all around performance.
Throttle response will be great,yes you will give up some top end.Most of the time you will run out of road before winding it out anyway. For me I tend to go to the smaller cfm size. I run 1 750 AFB on my 472 Hemi, way under what it had before but it's a street only car now. My 2 cents.
 
for a mild 440 boulevard cruiser a 650 AVS carb will be lots, just my 2 cents worth.
 
Put the 800 on and don't look back! You'll be fine with that. ruffcut
 
I didn't put the cam specs in because it was way to early for me to walk to the shop with only one cup of coffee.
Its a lunati 494 intake/513 exhaust with 110 lobe separation
Compression is 10.0
Street car use
Not worried to much about top end
But nice lumpyy idle with good manners for the build
 
A 650 to 750 CFM carb will do just fine. The small 650 can surprise you with how well it can work. It's more a matter of what style carb you can manage/tune, Carter/EDE or Holley. The EDE RPM's will use more flow & RPM depending on the cam profile. If you don't car about max power/top end, a smaller CFM carb will be fine. The small carb can create great signal & throttle response.
 
I put 850 min on my customer builds. Unless they want more.
The whole idea of bigger heads is more flow, so I'm lost on the small block carb size plan.
 
I didn't put the cam specs in because it was way to early for me to walk to the shop with only one cup of coffee.
Its a lunati 494 intake/513 exhaust with 110 lobe separation
Compression is 10.0
Street car use
Not worried to much about top end
But nice lumpyy idle with good manners for the build
I don't understand the part selection combined with the statement about not being worried about top end? Sounds like a build that is geared towards 6,000rpm? Whatever the case it sounds similar to my build only mine is a 456 stroker, I'm running a 750 QuickFuel race carb, no choke, mechanical secondaries and it works flawlessly. That being said I enjoy a bit of spirited driving, shift at 6,000rpm and have 3:55's behind a 6 speed manual. This is why people ask for more info.

My driving style combined with the gearing, transmission, rpm range all go into the equation.. remove the gearing, the manual transmission, etc and now your talking about vacuum secondaries.
 
Thanks guys
I did make the build for 6k rpm but the reality is I really don't drive like that. But I can if I need to.
727 auto with 355 gears and a 27 inch tire. I think I'll keep the 800 on the shelf. If I go with the the 670 holley that will give me a little space since the math calls for 649.
 
Chryslers math started out at 750cfm,, And then went to 850, on smog motors. Your calculator may be lying to you.
 
Those cfm calculators are very, very, conservative. In my, and others experience, bigger run better on bbm. I would at least run the 800, since you have it, and since it is, in essence a vacuum secondary.
If you dont like it, then spend money on a smaller carb.
(As an aside, i followed that formula on a good running small block, put a 600 on it. It ran FAR better with a 780 that i put on later).
 
I would stay away from the SA carbs. Had one and nothing but trouble. Good old 3310 is what I use and they are all swap meet units. If I wasnt a cheap bastard a Quick Fuel would be on all my rigs.
 
I have a 750 vac sec holley on my rebuilt 440. I always considered a 750 the minimum for a 440. Seriously considering a 800 edelbrock avs2.
 
It's always a safe bet to go with a 4150/4160-series Holley 750 on an engine making anywhere from 375 - 450 HP. The engine is an air-pump, it will only pull 'X' amount of air, regardless of carburetor size. Engine Masters has a great video testing multiple size Holley XP carbs on a 450-ish HP engine IIRC.

Make sure you're running a dual snorkel breather assembly if stock to support the power potential.
 
To the OP. Don't put too much faith in your math. But as Wagonman said a 3310 Holley is perfect. Something new that matches a 3310-1 or good used one, would be excellent. Those were very flexible and provided all the airflow required, even for a more radical combo than you have.
 
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