My vette has 88k on it, and doesn't use any oil between changes to speak of. Perhaps a half quart in 3500 mi. It doesn't see alot of highway miles these days, just a lot of around town. I just changed the cam, installed a new radiator, water pump, thermostate, all hoses, new seals around the rad, went to roller rockers, changed the oil and transmission oil and filter. The instructions for breakin in the new cam call for the engine to be held at 2k to 2.5k for 20 minutes, which I did. By the way it fired right up, good oil pressure and no leaks. (phew!)Then the instructions call for a series of incremental rpm increases over a set period of time to 3.5k, which I did. The problem comes in when held at anything over 3k. Both pipes emit a lot of smoke. So as I was doing this, I went back and sniffed the air (no, not directally out of the pipes, just cupped my hand and wiffed it that way) It had no odor of oil being burnt and was not black and rich smelling, so lookin at it I determind it was white, and prob carbon buildup in the cylinders. Now, I've never tried this trick and wonder if it's a old wives tale, but have heard that spraying a mist of water in the carb while running at a higher rpm causes a chemical reaction in the combustion chambers, which removes carbon. Like I said, I've never done it and was wonderin' what y'all think?

Dave

we used to do it all the time. we just pour water in the carb slowly and keep the engine running i dond know if it helped but it did no dammage. you could try it but i would wait to see what joel &ken have to say i would trust there advice more than mine

It can help some, but don't expect a miracle There are "top engine" cleaners that you can use that work better, tho. Just pour it in yer fuel tank and drive.
If the smoke was not there before you changed the cam, tho, you may have an intake gasket leaking, tho it may not be that.
Have you driven it for any length of time, just to "blow it out"?

There's some GM Top Engine Cleaner that you can pour down your carb.  Ken told me about this stuff.  You can get it at any GM Dealership.  Get the liquid, not the spray and follow the directions on the can.  If there's carbon, it will clean it out.  Stay away from the smoke commin' out the tail pipes and hope no one calls the fire department.

I hate to say it, but carbon burns black, antifreeze burns white. Hope you don,t have a head leak or worse yet cracked block. Better check it out before you put chemicals through there. I've seen a lot of head gaskets leak in my cooling system business. You can get a dye to to put in your cooling system thats shows if you have exhaust in there. Or open rad cap while its running and see if the coolant is rising or smells like gas. Just my opinion, Good luck with her.

Gotta agree with my7T1 as far as coolant.  Be really careful if you are thinking of the water trick.  If you just dump some water in the carb like clifton has said (albeit slowly) you have the danger of hydraulic action blowing your heads off or cracking things(water doesn't compress).  A mist can do the job but if you are getting large carbon buildup (you should be able to tell on the plugs) it sounds like a fuel mixture problem.

Black smoke, I would think of mixture.

Blue smoke, definately oil

White smoke, would lead to moisture somewhere.

My engine, even with a crack in one bore still ran ok 'cause the crack was below the point of max compression.  I had some white smoke at startup due to moisture being in the cylinder and oil but once things heated up it all went away.  If you have a vented oil cap and are seeing moisture venting from it.  I would think of a coolant leak into the oil system.  If not, take the PCV valve out and hold your hand over the hole in the valve cover to see if you are getting moisture.

If you have a crack in the bore, the easiest way is to take all the plugs out and spin the engine.  The one that is cracked will spit moisture.

Hope this helps and here's hoping it's something simple.

Yes, the GM Top Engine cleaner is best.   I have used water in the past.  If you use a trickle it will clean.  It's not a chemical reaction with the water and carbon.  The water turns to steam, and you get a high pressure steam cleaner in the cylinder.  But only in the cylinder.   The Top Engine Cleaner will also clean the back side of the valves and the intake, as well as the exhaust side.

Don't overlook the simple.  You might be making the same mistake many others have done.   Water builds up in the exhaust system due to condensation when the engine is shut off and the hot pipes cool.  This water can lay there for a long time.   This is why exhaust systems rust from the inside out.

Running at over 3K free rev can produce enough heat to start evaporating the water from the pipes and mufflers.  Yes it does stink due to the crud inside the pipes.   If this is the case, it will clear up on it's own.  No harm no foul.  If it persists, then you want to start checking other things.  My guess is it will clear.  Very common but usually unnoticed.  It's generally not seen when driving, but in exstream cases can be seen.  Still can be normal.

It seems to be clearing up. I think I will still try some of the GM stuff. Haven't taken it out and tried it out yet with the new cam, but hope for some inprovement. I went to 1:6 ratio on the rockers, put some lighter springs on the advance, so we'll see what happens when we hit the pavement. I've built my fair share of engines, both gas and deisel, changes cams, heads and intakes and the like, but this is the first time I've ever had one do this. Personally, I still think it's carbon buildup, due to the around town driving, it hasn't been out of town in a long time and not hit very high rpm's

Thanks all, Dave

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