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  #1  
Old 01-29-2002, 06:22 PM
riverside riverside is offline
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Question Carburator up grade

I have a stock 1970 340 Duster with the exception of headers and edelbrock RPM manifold and holley 850 double pumper. I feel the carb is too much. I'm considering a holley street avenger in 670 cfm or 770cfm. Would the 770cfm be too much or should I play safe and stick with smaller carb. Car is a street car and has automatic transmission. Advise would be appreciated Dave
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Old 01-29-2002, 06:38 PM
jelsr jelsr is offline
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850 sounds awfully big. The formula for determining optimum flow size is; CID X RPM X Volumetric effeciency over 3,456. Try .8 VE for your computation. I think you'll find the 670 on the large side.
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Old 01-29-2002, 09:23 PM
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rumblefish360 rumblefish360 is offline
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Via math given, maybe. But however, another way of looking at it would be the HP output of the engine. Rated @ 275 from the factory, the addition of headers and manifold should really help it out. I'll ball park a figure of 325 HP. At tis level a 600 cfm carb can feed it. I would go up 50cfm to a 650 cfm carb. That should be plenty.
The 670 may to large but not imposible to tune. 700 cfm's carbs is just what the MoPar books recomend for a carb replacement and general use in hopped up engines.
Remember that the T-Q was 800cfm. This vac. spreadbore had tiny prim. bore size for ease of tuneing and idle. Not as easy with a big bore, even (or close to the same size) bore/venturi size carb. Like the Holley or AFB.
I would choose the 670cfm. It'll work well if theres a cam change in the future or not.
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Old 01-29-2002, 10:33 PM
BIG BLOCK BILL BIG BLOCK BILL is offline
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I'd go with the 770 if its a vacum secondary carb , a little bit of tuning and it should work very well .
BIG BLOCK BILL
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Old 01-30-2002, 12:55 AM
riverside riverside is offline
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Smile carburator up grade

As allways thankyou for your advise, I'll be going with the smaller carb.
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  #6  
Old 01-30-2002, 01:19 AM
ram indy ram indy is offline
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I have got a 340 in my Dart Sport and I too made a carb change for the worse. I had a Holley 600cfm and it worked great until the float got stuck. Then I bought a edelbrock 750cfm from work and it is running a little rich and im not to happy with it. I have a mild cam ported heads and single plane intake so my opinion is to go with a 600 or 650. I work in a parts store and alot of people have told me the avengers are great carbs and worth the money but put out alot of fuel but no matter which one you go with will be better than the 850 you have.
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Old 01-30-2002, 03:42 AM
Doug Wilson Doug Wilson is offline
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I'd use the 650/670. Or... using the old axiom "if this works, then this X 2 must work better" ... dual Dominators on a tunnel ram - probably need to spend some time tuning!

GOD BLESS AMERICA!!
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  #8  
Old 02-10-2002, 03:47 PM
340dusterprostreet
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Post carb help

Riverside: I kinda had the same question. I have a 30 over 340, m-1 single plane, 292/509 purple shaft, stock x-heads the 2.02 1.60's with a Holly 750 vac. sec. Carb. upgrades 50cc accel. pump,
4.5 power valve and adjustable secondary spring kit. seems to work well. It is a 3100 lbs 71 duster tubbed w/ 29x15.50's 4.10 gear 904 tranny/w cheetah manual valve body. The car has turned 12.62 w/ full exhaust with those street tires (sportsmans pro). My question is do I need a bigger carb. A recent article build up in Mopar Muscle on a 360 they got the best horse power with a 950hp box stock with 1 inch untappered four hole spacer.
72 dodge challenger 3,000 stall with 3.55 gear.

I do run the Jacob's energy pack with the 8.5 wires and have plugs gapped at .050. If I was to look at those numbers in that book, I would say I need more carb. Any suggestions?
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  #9  
Old 02-10-2002, 09:15 PM
CL440 CL440 is offline
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iVE GOT A PERFECT 3310 750 (VAC SEC) HOLLEY I TOOK OFF MY 440 IN FAVOR OF A BIGGER HOLLEY (850) WHICH I HAVE YET TO PURCHASE. WHAT MODEL IS YOU 850 AND COND. WANT TO DO SOME HORSE TRADING?
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  #10  
Old 02-11-2002, 06:33 AM
riverside riverside is offline
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Post 850 carb

Sorry Sold carb last week.
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  #11  
Old 02-11-2002, 07:44 AM
CL440 CL440 is offline
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O.K., WELL IF YOUR INTERESTED IN THE 3310 (750) HOLLEY I HAVE, EMAIL ME AND I CAN GET SOME PHOTO'S TO YOU.
clewis@tc3net.com
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