Hello,

I have a 305 TBI in a GMC Sierra. The engine is releasing smoke out the exhaust system. The thing I can't figure out is that the smoke is white however the coolant levels are not dropping and the engine is not over heating. Also I should add that the smell of the exhaust gases are not sweet smelling as you normally get from an engine with a head gasket issue. I then wondered if the truck was burning oil and the smoke was blue but I had a friend confirm the colour and he says its more grey/white then blue. Fluid levels (except for gasoline) don't seem to be dropping.

I was wondering here...if the engine was running really rich from lets say a bad map sensor or a faulty o2 sensor...could this possibly cause the smoke that I am seeing?

 

Does it smoke all the time?

Just at startup until warmup?

When you pass on the freeway?

Only after it warms up?

I have had valve seals do what you are saying on chevy small blocks. They weren't burning enough oil to drop the level much, just enough to make the annoying smoke. Over fueling is almost always darker, and the very beginnings of using coolant can be so small it is hard to tell as well.

I'd do a compression check first and then a leak down test next.

 

Smokes all the time. The more you push the accelerator down, the denser the smoke gets. I tried using a thicker oil as my friend mentioned that what he did and it didn't make a difference. I will have to get someone who knows how to do compression test because I don't have the tools or knowledge on how to perform that task.

Hopefully its just seals and a head rebuild fixes the problem. I was almost tempted to go to the local gm dealer and drop a crate 350 in it but if I can save some cash on this build then I'd rather go that route.

 

"Smokes all the time" usually means piston rings. A crate motor can easily be cheaper than the cost of a rebuild when you add in machine work. This is especially true when you are not too mechanically inclined.

Just something to think about.

 

I think I am going to go that route. This engine has well over 300,000 on it and it would be a waste to bother to rebuild it. Crate 350 would cost me alot less. Thanks for the advice.

 

at least the money spent is going to be kind of fun, 350 ought to pick the truck up a bit.

 

On my lo3 the oilreturns in the heads were blockt by sludge so the oil level was above the valveguides. It smoked all the time but didn`t take much oil, it was also grayish white looking.

 

just outta curiosity....how did you fix that?

 

I lifted the valvecovers and ran a screwdriver threw the oilreturns to clear them, i changed the valveseals aswell when i had the valvecovers off.