I've been having a problem for the past 2 or 3 weeks with the 350 in my truck (used to be in the camaro). I had an exhaust leak for a couple of months and finally fixed it. Then the truck started running like crap. As far as I know, I didn't undo anything or mess anything up. It only happens at very light throttle, while driving slow. I guess I would call it a miss. It doesn't backfire or anything, and once it gets into the main circuit of the carb, it's fine. So far, I've replaced the power valve in the carb, checked and reset the idle mix, new plugs and wires and different cap/rotor, cleaned the carb good around the air bleeds. The old plugs were the color of a brick, not quite brown, but red. The new ones don't have any discoloration on them after driving, and it shouldn't be running lean. I'm running the same jets that I started out with, and it ran fine like that for about 5K miles. The only thing I can think of is that either there's a problem in the carb, or a vac leak under the carb. I have a 1" Summit phonelic spacer, and the gasket may not have lined up quite right, causing a vac leak later on. I do have a spare carb I can put on if ya'll think that sounds like the problem. This is driving me crazy. It is the engine described in my sig, if any of the specs matter.

 

Anybody? Come on guys, I know somebody has an idea.

 

I was waiting for you to come back and say you knew you did or did not have a vacuum leak.

Sounds like an idle circuit thing or a vacuum leak.

 

Check and see that your PCV is setup and working correctly, that will cause idle and light throttle problems.

 

I might have a vaccum leak in the carb gasket, but I havent had a chance to put new ones on. I'm not running a PVC right now. I was going to ask how to hook it up next. It looks like it just goes to manifold vaccum, but I thought that would just be a huge vac leak, and make the engine run like a dog.

 

Hook up the PCV with a new valve. Yes, it is a "huge vacuum leak", but the carb is designed to account for it. Without it, the carb won't work correctly.

 

I have a PVC connection on both valve covers. I can get some tee connectors and run it off of the vac hose for the brakes. Just to make sure you know, I have a Holley carb. I didn't think it would make any difference on there if I had the PVC hooked up or not. I just started a new job working all friggin day, like 10 - 12 hrs, so it'll be the weekend before I have a chance to mess with it again.