[Joe G]

I'm thinking of replacing the Holley 750 DP on my 69 as it runs way too rich. I borrowed a 650 DP from a friend and it seems to run better (doesn't burn your eyes). I am going to rebulid the 750 since it's off to make sure that isn't the problem.
The question is if a 650 is big enough for a 396 that tops out at about 5800 rpm. The info I have read on thoeretical needs put it at about 600-650, but since GM put a 780 on the big blocks originally, I think I'm missing something in the calculations.
I don't plan on racing it, but don't want to choke it down either (except for an occasional run down the strip at Sears Point and back roads ).
I have a TH400 and have been reading where a DP is not good so I'll go vac secondaries if I buy a new one.
Any suggestions would be appreciated.
Thanks, Joe

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69 SS396 Clone, B&M TH400, 12 Bolt Posi, Blue w/White Z28 Stripes
Badboatdude@CS.com

[This message has been edited by Joe G (edited 02-04-2001).]

[jvolk81]

You can definately make a 396 run very well off of a 650cfm Holley. Most people tend to over-carb and engine anyway. It will work good especially b/c of the modest rev limits.

Also, if you are looking for better drivability/mileage (i.e. less headaches) a vaccum secodaries carb will be great for street use.

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68 Camaro 396 powerglide 3.73posi
Soon to be daily driver
jonvolk@hotmail.com

[This message has been edited by jvolk81 (edited 02-04-2001).]

[Joe G]

Thanks for the info. I think for what I am going to do with the car the 650 should be better. Seems to have better throttle response.
I'm not sure what the redline is on this moter; It's still pulling hard at 5500; I'm reluctant to go any higher.
Joe

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69 SS396 Clone, B&M TH400, 12 Bolt Posi, Blue w/White Z28 Stripes
Badboatdude@CS.com

[This message has been edited by Joe G (edited 02-04-2001).]

[BRY67]

well I have a 396 with stock rods and crank w/arp bolts in the rods and I turn 7000 all day long, the engine is easily strong enought to handle 6500 and if you do the math the safe piston speed is right around 6500 so spin it up man! and by the way for your application, you should try a 750 vac. seconnday it will run better and make more power all around it has been proven in alot of tech books that in street trim the vac sec. carb will make more power all aroun than the properly sized mech secondary...give it a shot and come and tell me how good it ran!!

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<UL TYPE=SQUARE> 67' Camaro 408" <LI>BBC, 598 HP. th400 3500 stall
<LI> 3.90 gears
<LI>best of 11.50 @ 118 MPH (Street Driven)[/list]

[bruce69camaro]

i also have a 408 big block and i run a 780cfm. i ran a 650cfm through the program i have and between the two size carb's, it favor's the 780cfm. i don't know if that helps you or not, but i agree with bry67, use the 750cfm.
bruce

[Joe G]

Thanks for the input, guys. This is a great place to learn. Any thoughts on brand? Some friends of mine swear by the Demon.
Since the factory put on a 780, I think you're all right; a 750 would make more power. robably would be just as responsive as this 650 I'm using.
Joe

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69 SS396 Clone, B&M TH400, 12 Bolt Posi, Blue w/White Z28 Stripes
Badboatdude@CS.com

[bruce69camaro]

the speed shops i've talked to swear by demon carbs. they both have dyno machines and they swear, for cost vs. hp, the demon is the best buy. they said that the holley hp series is a very good carb, but needs a little work to make it perform good, but the demon works great right out of the box. i don't know though, i run a good old trusty holley and seems to work great. but i think i would buy a demon, when needed.
bruce

[pdq67]

A 750cfm 3310 Holley right outa the box is supposed to be set up for a 375hp/396. Thats why they are always rich on a 350 small block, or so I'm told. pdq67

[Joe G]

Thanks for the advice guys! This is a great site.
I just rebuilt the 750, so I'll give it another shot before I buy a new one.
7000 rpm on a stock 396? Pretty brave!
Joe

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69 SS396 Clone, B&M TH400, 12 Bolt Posi, Blue w/White Z28 Stripes
Badboatdude@CS.com