Thread: *Poor Throttle Response*

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I have a 1971 350 sbc (double hump heads) with a Demon 625 carb setting on an aluminum high rise, headers, nice cam. It runs great but at Idle when I pop the throttle it stumbles. It smells a little rich at the exhaust. What is the easiest way to tune this carb?

Do you have this document?

http://documents.holley.com/lit701rev10.pdf

Check the accelerator pump. If there is another setting available which would give a bigger squirt try that. If you're running a vacuum advance check the dapshot.

Must disagree with Denny. The aluminum high-rise, dual-plane intake manifold has shown through extensive dyno testing to produce the highest horsepower and torque readings of ANY naturally-aspirated intake manifold being produced today. All it will take, in my opinion, is a little carburetor tuning as offered by Glenn in post #2.
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What is your initial timing set at? Does your distributor have a vacuum advance? I have found that using a vacuum advance, connected to manifold vacuum, really helps throttle response on a mild street engine. Along with proper carburetor tuning of course.

Originally Posted by DennyW

"aluminum high rise" That's your problem...

Had to laugh at this one as it reminded me of a friend who years ago put a Torker II manifold and a 750 DP Holley on a stock 283. We lived at over 5,000 feet as well - what a dog. He burned up a lot of clutches before swallowing his pride and admitting he'd made a huge mistake!

That said - I've used my share of Performer RPM, Holley, and Weiand dual-plane manifolds with great success - typically with 650cfm Edelbrocks or my favorite - 750 Quadrajets. Zoom Zoom!!

Thanks for the input guys.

An aluminum high rise manifold is a little like saying you have a 3/4 race cam. You either have a dual plane or a single plane intake manifold. Not to be hyper-critical, but a person needs to be specific. It makes a lot of difference.