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What size carb?
If you use the formula motor size (cid) times max rpm divided by 3456 will equal the size of carb for the motor. Then you use the VE of 85% for street motors, 90% for modified motors and 95% for race motors. If I plug in the formula 408 cid 6000 rpm =2448000/3456= 708cfm x .90(VE 90%)=637cfm. This should be the wright size carb but what part does the size of cam and the heads play in how this will work? The motor is a 408w solid roller 610 lift vic jr world products wind sr ported and polished. Thanks for your input
Cheers Greg |
I'd put a 750 double pump on it....and I would probably even go with an 850 if it had vacuum secondaries. The formulas are usually wrong. ;)
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I Agree with Brent.
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Ok right now I have a edelbrock 1411 750 cfm carb and I would assume by the above statements that to go to a holly I should use a 4779 750 cfm double pumper or a 80770 street avenger 770 cfm vaccum. Which would be suggested for street and autocross. I can't get the stumble out of the edelbrock so I am changing the carb.
Cheers Greg |
I'd vote on the vac secondary. Light car, mech sec and dbl pumper, you'll just shock/overpower the rear tires that much easier. You can easily tune how fast/how soon the vac secondaries come in on the Avenger series Holleys by changing the springs in the vac module. Yeah, I've used mech sec/dbl pumpers, and they have their place.
I'm building an FE stroker to 455 cu.in., and I've got both 770 & 870 Avengers, I'll try both and see which works the best on mine. I've also gave up on the Edel carb's; they're a good carb with a stock to mild cam, but once you get into a big cam, they're much harder to tune and get right, in my opinion (for whatever its worth?!?!?) compared to a Holley/Demon/etc. |
Size carb
First, get rid of that Edelbrock. Ran one for years and never could get the secondary transition right. Switched to a Holly Street Avenger 770 with vac secondaries and not only runs smooth but the power improvement over the Edelbrock was quite noticable. I have a 408W as well but probably not as heated up as yours. Hope this helps.
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Quote:
Recently replaced it on my 408W with a Holley 800 cfm double pumper and my only regret is not doing it months ago. :) |
Well it looks like a 770 street avenger will do the trick thanks for all the help!!
Cheers Greg |
Dude, don't put the street Avenger on there.
Call Pro-Systems and tell them what motor you have and get one of their double pumpers. Patrick will tune it for your zip code by current weather. You'll pick up about 20 or 30 HP over that Avenger and your power will be linear and like a light switch if you punch it. Pro-Systems carb on car in video link below. |
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