Carb Size
#6
Mopar Fanatic
peterparr, tell us more about your combo, car weight?,cam?,tranny?,rear end gear ratio?,tire?,street or strip? it all depends on all those factors.
john
#7
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Join Date: Oct 2011
Location: Cesspool, South Carolina
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Only on a full out racer is a larger carb (900CFM or larger) needed.
#8
Mopar Lover
This month in "Mopar Muscle" magazine, there is an article regarding carb sizing for a mild 383 that they've been working on.
They used Holleys from 650-cfm to 1050-cfm and got the best results with an 850-cfm #4781 Non-HP with mechanical secondaries....
The article also stated that the "most dramatic" increase was when they went from a 650-cfm to a 750-cfm.
I was disappointed that they didn't do a base line test with a Carter AFB or AVS.
They used Holleys from 650-cfm to 1050-cfm and got the best results with an 850-cfm #4781 Non-HP with mechanical secondaries....
The article also stated that the "most dramatic" increase was when they went from a 650-cfm to a 750-cfm.
I was disappointed that they didn't do a base line test with a Carter AFB or AVS.
#9
Mopar Lover
peter -
Like the other guys are saying - depends on what's been done to the engine and the purpose of the car.
IIRC Holley recommends about a 650 for a stock/mild street 440 and 850 for a more aggressive race engine.
That being said, my 440 has a bit of work to it (rated a little over 500 HP) and really woke up on the track going from a 750 vac to an 850 DP. The 850 has been on the engine for about 30 years. These days, since I don't race anymore, probably should go smaller, but it still works - so I'll keep it for the time being.
Check Holley's website, I believe they have a cfm calculator.
Archer
Like the other guys are saying - depends on what's been done to the engine and the purpose of the car.
IIRC Holley recommends about a 650 for a stock/mild street 440 and 850 for a more aggressive race engine.
That being said, my 440 has a bit of work to it (rated a little over 500 HP) and really woke up on the track going from a 750 vac to an 850 DP. The 850 has been on the engine for about 30 years. These days, since I don't race anymore, probably should go smaller, but it still works - so I'll keep it for the time being.
Check Holley's website, I believe they have a cfm calculator.
Archer
#10
Super Moderator
You can read the specs on my 440 in my signature. I had a 870 Steet Avenger on it and it was too much. I jumped back to a 770 and it was much better.
#11
Mopar Fanatic
Did a quicky check on Holley.com and not knowing max rpm range i used 6000 and went thru the steps to get an answer according to Holley. suggested size was 750-870 cfm. And that was with out checking the 'race' button, just the street button.
So that being said, a 650 MAYBE a bit on the small side...
So that being said, a 650 MAYBE a bit on the small side...
#13
Super Moderator
#14
Mopar Lover
Eric -
Just curious, did you try playing with the jets and were you running the correct size power valve based on vacuum? Mine was running rich as well, until I dropped to a 5.5 PV (manifold vac was about 11 in gear, and the original PV was a 6.5).
Sorry, don't recall what jet size we ended up with.
Yes, the 4-hole spacer did make a noticeable difference in low end torque.
Archer
Just curious, did you try playing with the jets and were you running the correct size power valve based on vacuum? Mine was running rich as well, until I dropped to a 5.5 PV (manifold vac was about 11 in gear, and the original PV was a 6.5).
Sorry, don't recall what jet size we ended up with.
Yes, the 4-hole spacer did make a noticeable difference in low end torque.
Archer
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