What size carb would be best for my setup ? - Team Camaro Tech
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post #1 of 10 (permalink) Old Jan 20th, 05, 09:50 AM Thread Starter
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What size carb would be best for my setup ??? I want to make the most power with my setup.. Car is mostly a strip car.. Im not concerned about street drive ablity .. Would a 1050 dominator be too big ??

Pistons are Keith Black forged 12 to 1's, but my block was 0 decked so im guessing my Compression is around 13 to 1 ?

Motor is a 468 BBC
Trans is a Turbo 400
Stall is a Hughes 4,000
Intake is a Victor Jr. 454R
Cam is a Crower Solid Roller 290/306 -651/677
Heads are open chamber GM 990 rectangular port ..
Heads have had alot of porting done ..
Rear end is a 9 inch with 4.11 gears
Headers are Hedman ceramic coated 2 inch
Weight of car is 3500 lbs with me in it ..
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post #2 of 10 (permalink) Old Jan 20th, 05, 12:27 PM
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CFM = CID X RPM X VE divided by 3456
CID = 468
RPM = 6500
VE(volumetric efficiency)= 1.00(100%)
CFM = 880
Use 110% to 130% of CFM on single plane intake and 120% to 150% on dual plane.
120% of 880 CFM(880 X 1.2) = 1056 carb size
This formula is a good starting point, but is not the exact way to determine carb size. The volumetric efficiency varies a great deal from one engine to another.

69 RS 355 Tremec 5-Speed 4.11's
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post #3 of 10 (permalink) Old Jan 20th, 05, 02:46 PM
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You don't need a 1050 with your setup. It is always better to be a little under carbed if you have a pretty heavy car and not a lot of gear and convertor.
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post #4 of 10 (permalink) Old Jan 20th, 05, 04:14 PM
 
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I had a different experience than oger with a Dominator, not saying I'm right just a different experience. My old 468 in my 3400lb. 67' had a modified 850 double pumper, it ran really good (10.87) at 121 with a small roller cam and oval ports. I decided to see if my buddies 1050 Dominator would do any better. After switching carbs I picked up 2 tenths and 3 mph. This was done at the track for a back to back real world test. Just my two cents
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post #5 of 10 (permalink) Old Jan 20th, 05, 06:54 PM
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If your oval port motor picked up with a 1050 you had problems somewhere with the 850 or the intake.
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post #6 of 10 (permalink) Old Jan 20th, 05, 07:54 PM
 
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My oval ports were fully ported with the addition of 2.19 / 1.88 valves. Flowed 330 / 240 cfm @ .700 The camshaft was also a little long on duration ( 250/260) Maybe that had something to do with it? The carb was a Carb Shop Stage III 926 cfm unit, the intake was a Dart single plane.
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post #7 of 10 (permalink) Old Jan 21st, 05, 04:07 PM
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For a normally aspirated motor, 130% is pretty optimistic. VE's can exceed 100% if the port size, cam timing, and intake are well matched for a particular RPM. Also, engines that do break 100% VE often have a vary narrow power band. But that is typically what you want for a strip car.

Dave
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68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #8 of 10 (permalink) Old Jan 22nd, 05, 07:23 AM
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BDS 502 you had a really good set of ovals. A lot of bigport heads won't flow that much. You didn't go to a Dominator just a large 4150 carb. What kind of MPH did it run?
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post #9 of 10 (permalink) Old Jan 22nd, 05, 10:52 AM
 
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Yes, the heads were a really nice set,fully ported and flowed. Tha carb I ran was a modified 850 double pumper, I had The Carb Shop rework it to flow 926. The mph was 120 with that carb. After bolting on my buddys' carb ( 1050 dominator pt# 8896-1) it went 123 mph. The only modification to his carb was a re-worked idle circut, he drove it on the street a lot.
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post #10 of 10 (permalink) Old Jan 24th, 05, 09:30 AM
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A good way to size a carb for a race engine...is to get a very accurate vacuum gauge and measure your vacuum at wide open throttle. For a race engine, you want to get close to 0.5 inches of vacuum at wide open throttle....hard to do on a big block with a single carb....hence alot of Race engines use twin DPs or even twin Dominators. For a naturally aspirated motor the smaller the venturis the more pressure loss to the motor and hence a decrease in peak horsepower....smaller venturis will provide better lower rpm throttle response though...because the velocity will be a bit higher and promote air/fuel mixing. Atmospheric pressure is 14.7 psi and you want every bit of that pressure in the intake manifold for max power output.....air going through a venturi loses pressure.....a larger venturi loses less pressure and hence can make more horsepower at the higher rpms. If TXZ28 has a 4.11 gear, a 4000 rpm stall converter and uses the car for mostly racing purposes and wants every bit of peak horsepower out of the motor.....I would go with at least a 1050 Dominator and probably an 1150 Dominator....my opinion.
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