1990 C1500 350, 72,000 miles, this is a new toy, after sitting over night, when you strat the engine a cloud of blue smoke exists the exhaust then it clears up, seems like i remember chevy having an issue with the valve guide seals failing early, is this what is causing the smoke?
If this is the case, i have changed these seals out before on a 396 with the heads on the engine using a compression check guage and back filling the cylinder with air to keep the valve in place while changing seal, is this possible to do on this engine? I also do not remember the trick to getting the valves set closing after removing for start up, seems like i remember after engine is back running you tighten the valve until it starts to tap then back off quarter turn?

 

Yes compressed air is the best way as long as you have no blowby....

 

Just did the same job on a 1989 GMC and it fixed it right up. I must be getting more patient in my old age because I was really NOT looking forward to doing it, but it wasn't near as bad as I remembered. I used to be the valve seal guy at my fathers shop and I remember hating those jobs. I got through this one fairly easily. I always set the rockers as close as I can then start the truck with the valve covers off, back them off till they tap, tighten till they just quiet down, and then give them an extra 1/4 - 1/2 turn to seat them. Good luck!

 

I built my nerve up over the weekend and replace the seals, that was an alday project, had to remove most of everything on top of the engine just to get covers off, all of the exhaust seals were gone, no wander it was smoking. The seals took care of the problem.

 

Excellent...yeah they are never fun, but worth the days effort! Glad you got it fixed and thanks for letting us know the results.