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Old 01-30-2008, 09:57 PM
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carburetor cfm ratings

I have two 2-barrel carburetors. I will use one of them on a strong running 1965 chevy 283 engine in a '35 ford pickup. I would like to know the cfm rating for each of these carburetors which are:

Rochester 2 Jet, it has GM stamped on it and another number 7031714

Carter Model WGD-4078S

Any information anyone can provide is appreciated.
Thanks
Rusty Duck

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Old 01-31-2008, 02:42 AM
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Old 01-31-2008, 06:40 AM
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Old 02-02-2008, 11:59 PM
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Beware of 2-bbl flow ratings. 2-bbl carbs are rated at twice the pressure differential (suction) as 4-bbl carbs and EFI throttle bodies. This means you have to reduce the 2-bbl flow figures by ~30% before you can compare one to a 4-bbl.

Multiply the 2-bbl flow number by 0.707 to get a figure that you can legitimately compare with 4-bbl numbers.
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Old 08-20-2010, 10:34 PM
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neutral safety switch

I have a Lokar floor shifter with neutral safety switch on a TH350 transmission that will not allow the motor to start in reverse, 1st or 2nd gears, but it will start in neutral, park, AND drive. I know it is not suppose to start in drive, but since it works correctly in all gears except drive is the switch bad or is there some sort of adjustment that I can make?
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Old 08-21-2010, 12:06 AM
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Quote:
Originally Posted by rusty duck
I have two 2-barrel carburetors. I will use one of them on a strong running 1965 chevy 283 engine in a '35 ford pickup. I would like to know the cfm rating for each of these carburetors which are:

Rochester 2 Jet, it has GM stamped on it and another number 7031714

Carter Model WGD-4078S

Any information anyone can provide is appreciated.
Thanks
Rusty Duck
If the 2G is a large base (1.50") carb, there are at least four different venturi diameters. They all have 1-11/16" throttle plate bores. They were used from the late 60's until about '79 on automotive applications.

1-3/16" venturi: 350 cfm
1-1/4" venturi: 380 cfm
1-5/16" venturi: 425 cfm
1-3/8" venturi: 435 cfm

The small (1.25") bolt pattern 2G carb had a 1-5/32" venturi, a 1-7/16" throttle plate bore and was rated @ 280 cfm. It was used from '55-'71.

Your carb is likely a '61 Chevy carb, w/small base and 280 cfm. The Carter is in the area of 320 cfm.

NOTE: All cfm ratings for 2-bbl. carbs are @ 3"/Hg. 4-bbl. carbs are rated at 1.5"/Hg.
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Old 08-21-2010, 12:12 AM
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Thanks Cobalt

I appreciate the info!
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Old 08-21-2010, 06:11 AM
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Quote:
Originally Posted by rusty duck
I have a Lokar floor shifter with neutral safety switch on a TH350 transmission that will not allow the motor to start in reverse, 1st or 2nd gears, but it will start in neutral, park, AND drive. I know it is not suppose to start in drive, but since it works correctly in all gears except drive is the switch bad or is there some sort of adjustment that I can make?
Needs adjusting, may find the Info on Lokar's site.
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