Why or Why Not?
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Joined: Jan 2002
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From: Roswell, Georgia
Why or Why Not?
Can someone please explain to me why it is said that vacuum secondary carburetors work better with automatic transmissions and mechanical secondary carburetors with manual transmissions. I currently am running a vacuum secondary 600 with my T5, and am thinking about getting a new carburetor in the near future.
Joined: Mar 2000
Posts: 43,187
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
It's a generalization, but generally true.
The VS is more forgiving when punched, which the engine with the auto behind it appreciates because the amount the engine can rev is controlled by the torque converter - which isn't forgiving.
With a manual, you either a) have gears that allow the engine to rev into the powerband as soon as all four barrels are open, or b) you slip the clutch to allow the same.
FWIW, the "big boys" with drag race-only cars and high-reving engines typically have steep rear gears, loose torque converter, and a Holley double pumper.
The VS is more forgiving when punched, which the engine with the auto behind it appreciates because the amount the engine can rev is controlled by the torque converter - which isn't forgiving.
With a manual, you either a) have gears that allow the engine to rev into the powerband as soon as all four barrels are open, or b) you slip the clutch to allow the same.
FWIW, the "big boys" with drag race-only cars and high-reving engines typically have steep rear gears, loose torque converter, and a Holley double pumper.