I have a 80 elk w/305 in it. it smokes but not constantly on the highway it only does it when i slow down in traffic then it stops but doesn't always smoke when i start moving again. It also sometimes smokes when at a light but again not always. the smoke is more white than blue and it doesn't smell sweet. Any ideas?

Check to verify where the smoke is coming from. If it is coming from the exhaust pipe, it is most likely the result of worn/leaking valve guide seals. Engine oil leaks by the worn seal, down the valve shaft and into the cylinder where it is expelled via the exhaust pipe. At cruising speeds, smoke from leaking seals is usually not visible. It is almost always seen when accelerating from a stop after the engine has been idling for several seconds, such as at a trafffic light.

If you have a vacuum modulator on the transmission, check the vacuum line at the carb or manifold where it's plugged in for trans fluid. Trans fluid gives white smoke and I've been told that a pinhole leak in the modulator diaphram will suck trans fluid back to the intake. Anyway, it's easy to check.

I have a 80 elk w/305 in it. it smokes but not constantly on the highway it only does it when i slow down in traffic then it stops but doesn't always smoke when i start moving again. It also sometimes smokes when at a light but again not always. the smoke is more white than blue and it doesn't smell sweet. Any ideas?

Could be the head gasket. Sounds like steam. Unburnt oil is generally blue, the modulator valve on the tranny could be going bad, I've seen that leak. If it is you really need to take care of that it will cause a lot of problems if it continues.

If the head gasket is bad then you probably should have to heads surface checked. Has it gotten really hot in the past?

Just off the cuff I'd say that what you are seeing is steam. When you slow down it pulls more vacuum and could be sucking in more water / coolant. Gas is usually a Black smoke or dark gray color and noxious smelling.

Sorry to hear your Elky is sick.

Good Luck.

Have you checked your fluid levels? (oil, coolant, tranny, brakes) Any of them going down? All are possible causes of a smokey exhaust.

your engine could be either burning or using oil. it is a common problem on engines with alot of miles on them. i have this same problem with my 89 s10 blazer.