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Old 01-12-2013, 06:26 PM
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Originally Posted by Ltsulli1 View Post
Ok man, got the truck running and idling ok..... Now we have another issue that's kinda stopping us. I tuned the carb I set the timming good it will run and stay running fine but now when I put it in gear it dies out.... I can keep it running in gear with the idle turnt up or foot on gas and keeping it running! As soon as I let off it kills. I have a correction it is a comp thumper cam NOT a mother thumper. We were told we shouldn't have to have a stall with this cam. Are there any tricks am I missing something? There are no vacuum lines to the trans nor cables atached to the motor/carb from the 350 turbo trans. Thanks for any input!
The key to making the thumpr cam behave is more initial timing. I'd start w/about 22 degrees BTDC and work up or down as needed from there.

Vortec heads only need 32 degrees total timing, not counting vacuum advance. More on setting up the timing correctly is linked to below. Until you get the timing sorted out, you're going to have a hard time w/idle quality, nozzle drip, off idle response, etc.

Use a vacuum advance limited to 10 degrees, use ported vacuum for it.

If you find you're still having a problem getting a balance between idle quality and initial advance (advance isn't helping enough), you may need to add idle bypass air.

Not all Q-jets have a threaded rear port for a power brake booster. Use a manifold port if yours doesn't. The front large vacuum port is for the PCV valve.

Carb vacuum port ID

Advance curve

You most likely do need more stall, but sort the timing out first, then see what you need if anything.

Last edited by cobalt327; 01-12-2013 at 06:33 PM.
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