Perplexing smoking problem with GN1 heads?

[GSX-PKV]

I have a new motor with GN1 heads that has 600 miles on it. The motor runs really great... but at idle (especially after reving the engine), and when "letting off the gas", grey smoke wisps from the exhaust pipes. It seems to happen only at high vacuum, no smoke at all is seen at W.O.T. The engine does not appear to be using any appreciable amount of oil or water.

I took off the inlet pipe and the inside side of the throttle had a lot of oil on it. I temporarily blocked off the pcv vacuum line (I have 2 valve cover breathers) because that definately was one source of the oil in the intake... but even with that I still get grey smoke. I've driven about 75 miles since I did that, if oil got into the intake, I wonder how long it would take to drip down and burn away?

Do your GN1 heads smoke at high vacuum??? Any ideas would be appreciated. Paul

 

[turbosam6]

Hey Paul, hows it going? You goin' to the dyno Saturday? I'm not sure where the smoke is coming from, but you might want to check the oil, as blocking the PCV can milk that stuff up in a hurry! Just don't want to see ya screw up that nice new motor. Did you ask Pete about the smoke?

 

[WIKEDV6]

Try some GM sealing tablets and see if the smoke goes away, lot of people run them with GN1's to be on the safe side. I do.

Good luck
Prasad

 

[GSX-PKV]

Thanks. Do I just go to a dealer and ask for sealing tablets? Are they for the radiator? Thanks for the tip. Paul

 

[KendallF]

When I've seen that high vacuum "let off the throttle and it smokes" problem, it's usually been the turbo seals.

 

[JCotton]

Not sure I see the relationship between new GN1 heads and smoke. We install and use GN1 heads on many new motors here, have never had a smoking problem related to them. I have seen other manufacturers valve springs break the inner damper spring and grab the valve stem seal damaging it, causing oil consumption. But when you say there is a good amount of oil in the Tbody, you may want to check elsewhere. Possibly the turbo or some other area that was modified from stock confiquration.

 

[GSX-PKV]

The turbo is brand new. there was no oil on the outside of the throttle blade or in the inlet pipe from the intercooler. I removed the exhaust downpipe and there was no oil on the exhaust side of the new turbo either. Thanks, Paul

 

[ijames]

If there's no oil in front of the throttle blade then it has to be coming from either the pcv or a vacuum leak into the lifter valley. I think you'd notice a leak from the rough idle, and the pcv pathway is notorious for this. I also don't think the oil that's in there will ever go away by itself. Pull the uppipe and hose out the insides with a can of carb cleaner. You may want to pull the doghouse to be extra thorough, especially if you have a power plate so you can't really spray down the runners. [Don't let the little red tube fly off the can and go into the intake or you will be pulling the doghouse - don't ask .] Fire the engine up and let it idle for a minute or so to suck everything out of the intake, then change the oil and filter to get rid of the junk. You may want to check the plugs afterwards, too, and it will start like it's flooded so mash the gas pedal to the floor then lift slightly to get into clear flood mode where it won't squirt any fuel, and then crank till it catches and then get off the gas as the rpms come up.

 

[GSX-PKV]

Problem solved! Thanks to everyone for your input. To clean the oil in the plenum from the bad PCV valve, I removed the upper plenum and found that the source of the oil was a bag intake manifold gasket where the #6 cylinder was sucking oil up from the valley and down the runner into the head. No doubt about it! It will be nice to go smokeless again! Thanks again. Paul