Re: Need some help with this old carb...

supervel45 April 26th 2016, 3:00 am

If your cam is anywhere near stock and pulls over 15" vacuum at idle I would put an 8.5" PV and check the acel. shooter number. If it is a .025 I would step up to a .031. You might also try opening the idle screws a 1/4 to 1/2 turn more and see how it does. All kinds of ways to cover a flat spot.

rmcomprandy April 26th 2016, 8:29 am

jbozzelle wrote:Still having issues with this carb. Changed out the dual stage power valve (blown) for a 4.5, cleaned it up and put it back together. Runs a bit better, idles much better but still has somewhat of a flat spot.

It does have 47 jets in it which seem awfully small to me. The truck came from Colorado at an elevation of about 5-6000 feet with low humidity. It's at sea level now with more humidity. Would it benefit from more jet? Might need to try increasing the pump shot too...

If you have not changed the idel SYSTEM by opening the idle fuel feed or making the air bleed smaller, you will have this ongoing problem on that engine.

Instead of making the idle air bleed smaller or the idle fuel feed larger just get a wire paper clip about .035" diameter wire and bend it so it wraps around the vent tube on the front of the choke horn with the ends inserted into the idle air bleeds like a metering rod. Use a little tape to secure it to the vent tube.

blown473 April 29th 2016, 11:38 am

The lever on top is simply a bowl vent that is opened at idle. This carb could be rebuilt by ordering the rebuild kit for a List # 7448 which is a 350 CFM 2BBL carb with bowls like this one.

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Need some help with this old carb...