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Old 06-01-2011, 03:38 PM
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New Carb.

This past weekend I decided to swap out my old carb. The vehicle is a 1988 K5 Blazer with a 383 stroker. I had an old holley 670 street avenger with no choke on it. The engine ran pretty good with this carb but because the lack of choke it would take forever to idle by itself. So now I have a holley 770 street avenger and an electric fuel pump thats regulated to 7psi.

The truck starts on the first crank everytime now but the engine now runs like crap. It has a very rough idle (worse when cold), it runs pretty rough through all rpm's untill you get to around 4000 then it starts running pretty smooth. It also back fires when floored from a dead stop and sometimes it will stall after flooring the pedal and then backing all the way off the throttle.

In short this carb needs to be tuned and badly. I have no idea how to properly tune a carb. Ive heard carburated engines run just as good as fuel injected engines so i know its possible. Again the carb is a re-maned (by a very good carb shop) holley 770 street avenger carb with an electric choke and stock jets.

Does anyone know of a good guide on how to tune a carb? Or if anyone has any tips or tricks on carb tuning that they would like to share that would be awesome. I know the idle will never be "smooth" because of radical cam I have in the engine but I know for a fact it can run much smoother than it is now.

Thanks for any help.

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Old 06-01-2011, 07:17 PM
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Start by making sure the float levels are set correctly, that you have no vacuum leaks, set the idle mixture using a vacuum gage, and make sure the choke is properly adjusted.
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Old 06-01-2011, 07:56 PM
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Quote:
Originally Posted by FmrStrtracer
Start by making sure the float levels are set correctly, that you have no vacuum leaks, set the idle mixture using a vacuum gage, and make sure the choke is properly adjusted.

I'm pretty sure I know how to set all that stuff but the choke is whats trippin me up. I know that the choke plate should be about 1/8-1/4 inch open when the engine is cold but other than that I'm not sure how the choke needs to be adjusted.

I don't think I have any vaccum leaks but I'll know for sure when I bring my vacuum gauge home from work.
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