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tbrown8338 02-06-2012 07:33 PM

chevy 350 engine smoking
i have a 1973 chevy 350 engine that smokes a blueish/gray smoke at idle sometimes. it smells like gas but i have replace the carb. and adjusted it out. the engine runs and starts perfect hot or cold with plenty power and no rattles.the engine been rebuilt about 4 years ago and have been setting up every since. should i just drive it a little bit and see what happen because i only have driven it about 20 miles since i had it. from the best i can tell it only smokes at idle because going down the highway i didn't notice any smoke. i have had a vehicle that had bad valve guides that smoked very bad at start up but this smoke is not hanging around like that it comes out in little puffs and some times none at all.. please help

tbrown8338 02-06-2012 08:40 PM

can the carb. cause a chevy 350 to smoke at idle

66GMC 02-06-2012 09:10 PM

Has the engine ever actually been broken in since "rebuilt"?

I'd say "drive it" for a while. Get a feel for the oil consumption, if any.

Check the PCV valve and hose at the back of the carb and transmission vacuum line for a show of oil. An intermittent puff of blue might be a couple of drops of oil getting sucked in from something like that.

It's also possible that valve stem seals may have dried up a bit after having sat for 4 years.

If the problem persists, I'd suggest that you pull the plugs and read them.
If you put a mark at the top of each spark plug base (and find the plugs to be oil fouled upon removal) you'll be able to determine if the oil is coming from the top (valve seals, PCV, trans modulator, etc) or from below (i.e. rings)

If it's running rich (fuel smell) it may be that some of the debris / sediment from the fuel tank might be working its way thru and interfering with the need & seat in the carb. Check & replace, if nessecary, the fuel filter while putting a couple of tankfuls through it.

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