Okay, I'm running a Holley 670cfm Avenger carb on a 78' 350 (rebuilt) in an 82' Camaro.

At idle, it runs fine. It lopes nice and all due to my cam.

but I noticed something just a few min ago. When I rev the car up at idle, I'm getting black smoke. What could this mean...to rich? to lean?

Any takes?

I'm thinking carbon. If the engine hasnt been run hard in a long time, it might have some carbon built up. I know when my cousin put a 350 in his 88 RS, carbon blew EVERYWHERE and we got it all over the garage door and my grandmas 7-8 grand lawn mower. Set a piece of cardboard behind the exhaust and see if it deposits on it. You might just have to "clean it out" as they say, and give it alot of moderate revs. Thats what he had to do, that and run it for 20 minutes straight to break it in(it was a brand new engine)

I'm no expert though, but in my(little) experience, it could be carbon build up.

Sounds a tad rich at tip-in. Tuning Holley carbs is easy after you get the hang of it, may want to buy a paperback book on the subject.

There are basically four tuning variables on a Holley:

1.) idle air adjustment: screws on either side of the front metering block.

2.) accelerator pump: there's a crescent-shaped "cam" actuated by the throttle shaft, which in turn actuates the accel pump. You can interchange these to bring in the gas sooner/later and to varying degrees.

3.) main jets: you have to remove the bowls and metering blocks, after which you'll see 2 jets in each metering block. There's a number stamped in each jet telling you what size (72 for example).

4.) power valve: also located in the metering block, this is vacuum-actuated and opens as vacuum drops (eg. you open the throttle) to release more fuel into the venturis. There's a number stamped into the metal facing telling you at what vacuum the valve will open.

Offhand, if the car runs rich all the time I'd say the main jets may be a tad big. See what size they are, then jump on Summitracing.com or hit the local parts shop for smaller ones.

If the car only runs rich as you tip in the throttle, the power valve may be opening too soon. See what vacuum open yours is, and get one with the next size lower number (opens later). After you've gotten the power valve as close as possible, you can start playing with accel pump cams...don't try tuning both this and the power valve simultaneously or you'll miss the right combo.

Man, answered a ton of questions, thanks guys.

BTW, I'm know where I can find a diagram of all Avenger carb so I know where adustments are?

And also, do I adjust the air/fuel ratio with the idle air adjustment???

I need a book..haha.

You're really asking a carb question, not a motor swap question.

On the Carb forum, there's a sticky that includes this link http://www.holley.com/HiOctn/TechSer.../FMCTech.html. Give it a look.