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Username Post: Carter AFB Vacuum Question        (Topic#101617)
Silver Supporting Member
Posts: 4988
Loc: Nova Scotia, Canada
Reg: 08-21-01
05-22-05 10:25 AM - Post#701983    

I have a Carter AFB, 3721SB B5 are the numbers on it, 4 barrel. Is there a difference in how it would get vacuum if it is set up for a Powerglide or for a manual tranny? It has a vacuum line from the distributor to the front of the carb and somebody told me there is a difference. I want to use it on a manual tranny 327. It's running rich, my mechanic thinks it's not getting any vacuum advance at idle, because it's getting vacuum from the intake and should be getting it from the venturi.

The question is, is the port on the carb in a different place for a manual than on a PG?

62 Bel Air SC, 59 El Camino (sold), 62 Bel Air SC(sold in Finland is 2011), 63 SWC Vette (sold)
Member #2194


Re: Carter AFB Vacuum Question
05-22-05 10:53 AM - Post#701984    
    In response to DonSSDD

the manifold gives you full vacuum at idle,ported vacuum only gives you vacuum after you crack the throttle. the 3721 carb is for a standard shift 1964 corvette with 300 HP the carb should have a .104 pri jet,.069 secondary jet and .060 X .069 metering rods,float level 7/32" pri and sec and 3/4" float drop

Valued Contributor
Posts: 2972
Loc: Heart of Dixie (Georgia)
Reg: 06-25-00
Re: Carter AFB Vacuum Question
05-22-05 01:07 PM - Post#701985    
    In response to DonSSDD

The vacuum port that you want to use for the vacuum advance is the port on the driver's side of the carb in the front. The passenger side is for "ported vacuum" only and should NOT be used with your application.

I don't know who your mechanic is, but he should be able to tell the difference when vacuum is present.

The tranny should be signalled from the intake manifold...again full vacuum all the time. And moreover he should realise that vacuum is present at the intake too....not just the carb port.

Its real easy to tell if vacuum advance is present at idle. Simply by pulling the lead off the vacuum advance can will show a marked difference in timing (less timing).

Goooooooood luck.

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