Thread: dual 4 barrels

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Here's a Q that my antique mind has been pondering: If you use the rear carb as the "primary carb", wouldn't the fuel distribution from the primaries in it be more equal than if the front carb was used as "primary", since the front carbs primaries are all the way to the front of the manifold, as opposed to the rear ones being more to the middle?? This all being as if you used only one carb for a single pair of barrels at lower engine speeds; if both carbs are used in tandem, with the secondaries coming in at some predetermined point, then this question is probably moot.

Ooops! Tech, you beat me to it, by just one minute.

One set of primaries on a single 390 doesn't seem to keep the engine afloat; at least, not with the tunnel ram. It idles for about ten seconds and then sputters and dies. I tried running it on one 390 when I needed parts for the other; figured I'd just block off one hole and the related vacuum / fuel lines and run to Schmuck's on one carb, right? Not.

I planned on someday trying to run the carbs progressively until I tried to run on just one.

Richard, Rumbler your both right, never gave it a thought. Thats why I ask questions because sometimes this old mind of mine doesn't think right. Thanks for your input.

The more I got thinking about what you said, I have another question for you. If the front carb was used for your primary, wouldn't under acceleration all gas would move to the back carb, and if your rear carb was your primary one wouldn't the gas puddle in the back of engine and cause the front cylinders to starve for gas? Just my thought.

I don't think the horizontal G-forces on such a lightweight thing as a fuel/air mix would affect it more than a negative pressure which will pull the air/fuel mix into the cylinders.

The rear carb is chosen since it's primaries are closest to the center.

I found on my 462" Buick the dual quads ran a bit rich at the front end.

Straight linkage fwiw.

Originally posted by chevy 37
The more I got thinking about what you said, I have another question for you. If the front carb was used for your primary, wouldn't under acceleration all gas would move to the back carb, and if your rear carb was your primary one wouldn't the gas puddle in the back of engine and cause the front cylinders to starve for gas? Just my thought.

If that were the case, I think all the manufacturers would have mounted the carb at the front of the intake instead of in the middle, wadda ya think??

I think that there is not enough TIME for the mixture to move anywhere except from the carb throttle bores straight into the head ports. Besides, a 180 manifold has runners to direct the mixture.

FWIW, here's an exploded view of my homemade carb linkage: