Black smoke from exhaust

[1981 ss chevy]

I read through the archives but couldnt really find an answer i needed.  So here is my problem, I have an 81 c10 350/th350 350 has edelbrock intake 1406 edelbrock carb headers.  It runs great starts however when going down the road and I floor it it runs awesome at about 6000 rpm and sounds great but the passenger exhaust tip has black some coming out of it and I have true duals no x or h pipe.  Supposedly that means running rich or unburned fuel.  Now how do I go about fixing this? new plugs? tune carb? adust timing?

[Irish_Alley]

Well since both sides share the fuel I don't its cause the Carb is too rich I would start with a tune up plugs wires and se what you come up with then

[1981 ss chevy]

ok im going with plugs because i got new summit plug wires when i swapped intakes only about 2k miles ago

[fitz]

it runs awesome at about 6000 rpm

What are you running for a cam that needs to rev to 6K to make power?

[bake74]

  Since you have a true dual exhaust, and it is only happening on the passenger side, you need to concentrate on the passenger head. ( anything that shares for both side would not be the problem, ie the carb,)  I would start with the plugs and see if any on that side are burnt, fouled out, or worn off prematurely.  Then I would move on to a compression check on that head on all cylinders and see if any or weak or maybe 2 or weak together (meaning possible blown head gasket), good luck and keep us posted on what you find.   Tom

[1981 ss chevy]

to my knowledge the cam is stock but idk the motor was rebuilt once before i got it.  and it makes power lower then that, thats just what it shoots up to when i hammer it and it shifts down

[1981 ss chevy]

bake74, if i had a bad head gasket it would be burning water then and the smoke would be white right?

[bake74]

   More than likely white smoke, but I have had some weird issues arise with blown head gaskets.  A compression check can do more than tell you if you got a blown head gasket, it can tell you if you possible have problems with your valves, rings, or a combination of things.  I was suggesting you just check a few things and get a good idea of what you have and don't have, then it will be a lot easier to diagnose and somebody here probably already went through it and could save you some time and money.    Tom

[1981 ss chevy]

Ive never checked the compression how do you got about doing this?

[Lt.Del]

get a compression guage from any auto parts store. Warm up the engine. Take the hot wire from the distributor so the engine won't fire.
remove a spark plug.  Put the guage in and hold it tight in there.  Have some turn the engine over a few times times--it will record the highest compression reading.  After noting the pressure, reset it and try another cylinder.  The trick is to get a reading on all cylinders and see if any one or two are way off.  

At least that is how i did it years ago.   They make them with a screw in hose--that screws into the spark plug hole now--i didn't have that luxury back then.  So, only one person can do a test now. Put oil on the threaded part that screws into the spark plug hole.

http://www.youtube.com/watch?v=XcmIPm8M3Xw&feature=related

[beastie_3]

You should be able to rent them at the local parts store, O'rileys is free.

[1981 ss chevy]

put in some new plugs now its good to go

[beastie_3]

did you ever check compression?

[1981 ss chevy]

was going to but oreillys in town didnt have one you could rent, you had to buy one so i just said screw that i tried new plugs and it worked, if it hadnt i would have had to buy a compression tester

[DnStClr]

Hope you found the problem but you may find it reoccuring if that head is bad. A compression tester won't set ya back that much cash and will come in handy. It's a great troubleshooting tool.