Re: What size carb size?
[Re: hemirambob]
#1032907
07/15/11 09:30 AM
07/15/11 09:30 AM
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Joined: Mar 2008
Posts: 5,746 Ontario, Canada
Dodgem
master
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master
Joined: Mar 2008
Posts: 5,746
Ontario, Canada
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A 750 vacuum will work real nice on the street. lighter advance springs for more idle advance would help. think I would recurve the dizzy first. check your in gear vacuum after at idle after you give it more initial/idle advance and go 1.5 to 2 numbers under that for your power valve. if you get 7 go 5.5 maybe up your idle rpm to 950 (or 1000 to 1100 )
Last edited by Dodgem; 07/15/11 09:31 AM.
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Re: What size carb size?
[Re: chargincharles]
#1032912
07/15/11 11:39 AM
07/15/11 11:39 AM
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Joined: Jul 2006
Posts: 4,319 Puyallup, WA
StealthWedge67
master
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master
Joined: Jul 2006
Posts: 4,319
Puyallup, WA
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OP might know more than he (& we) thinks.... 12.50's in a B body street car is WAY fast for that motor combo, and I'm sure the 950 sitting on top of it has a little to do with that. However, on the street, I think it would run much better with a 750.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: What size carb size?
[Re: StealthWedge67]
#1032913
07/15/11 11:56 AM
07/15/11 11:56 AM
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Joined: Apr 2007
Posts: 2,826 NY usa
540challenger
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master
Joined: Apr 2007
Posts: 2,826
NY usa
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Quote:
OP might know more than he (& we) thinks.... 12.50's in a B body street car is WAY fast for that motor combo, and I'm sure the 950 sitting on top of it has a little to do with that. However, on the street, I think it would run much better with a 750.
x2 Looking at his times if he plays with his suspension or loses some weigh he might be able to dip into the high 11's.
To the OP are you looking to improve you time at the track or looking to tame it for the street.
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Re: What size carb size?
[Re: 440CIVIC]
#1032915
07/15/11 01:15 PM
07/15/11 01:15 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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Two suggestions and a comment: 1. Holley 750 vacuum secondary would be much crisper on the street and off the line. 2. Shorter duration cam will lower the ET dramatically. The 60' time is slow IMHO.
Now on to carb size. IF you are racing dynos then bigger is better. Lower restriction in the intake allows better cylinder filling equals more hp. For this reason the cubic inches times rpm over 3456 equation doesn't work for race cars. It will result in a 1.5" depression across the carb. I remember dyno tests where the intake depression or vacuum was measured and the hp kept increasing as they lowered it to 1/2 inchby running larger and larger carbs.
Plain and simple the reason one drives a smaller carb on the street is what happens at part throttle. If you get the primaries too large the carb signal is weak and metering goes to heck. This is the rationale behind the Q-jet and Thermoquad.
It is possible to run a larger carb on the street if you use the right booster to get decent signal. I'd say Holley tech people or a good Holley tuner might be able to help the OP keep the 950HP carb and increase drivability, too. And on the Holley HP carbs the boosters are changeable.
R.
Last edited by dogdays; 07/15/11 01:20 PM.
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Re: What size carb size?
[Re: hemirambob]
#1032916
07/15/11 04:42 PM
07/15/11 04:42 PM
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Joined: Nov 2006
Posts: 1,459 oklahoma
forphorty
pro stock
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pro stock
Joined: Nov 2006
Posts: 1,459
oklahoma
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I have no personal experience with the 950 hp but everything i've heard about them has been positive. It's really not that big anyway. It's essentially a 750 mb with radiused entry combined with a 850 bp. Plus, dual plane intakes are more tolerant of big carbs. You may need more initial timing. That cam is pretty hot for a street 400. I would say your problem has more to do with cam, ignition or carb tuning than carb cfm. Are the plugs fouling? You might try leaning out the primaries. I sure wouldn't go changing out the carb just yet. Oh, that cam would probably like more converter than what you have.
Last edited by forphorty; 07/15/11 04:48 PM.
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