Thread: Smoke Out Tailpipe

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I rebuilt a 283 for my 65 chevy truck. I have driven it about 3000 miles and I noticed smoke coming from the tail pipe when I change gears. It's a three speed. Any one have any ideas of what it could be?

White Smoke-Very dense, white smoke present in vehicle exhaust gases is symptomatic of transmission fluid being sucked into the engine's combustion chamber and burned. This white smoke is not normal and, if present in the exhaust, generally indicates a problem with the transmission modulator valve. This problem can typically be corrected by replacing the modulator valve.

Black Smoke-Black smoke is the result of partially-burned gasoline being carried down the exhaust. This unburned fuel is wasteful, expensive, and a carcinogen. Black smoke can usually be eliminated with carburetor or fuel injector repairs.

Blue Smoke- Pale, bluish-white smoke is the result of engine lubricating oil being burned in the engine's combustion chamber. The most common causes of blue smoke in the exhaust are worn piston rings or loose valve guides. Both conditions involve major engine repairs to correct. You can often diagnose the source of this blue smoke by performing an engine wet/dry compression test.

Additionally, you put the qualifier in there that it smokes when you shift. I assume you mean when you lift on the throttle. Odds are this indicates the valve guides are worn. Either they weren't done at the rebuild, were knurled (which is a tempory fix), or they were done wrong (worn valves in new guides, poor quality guides, etc.). Sometimes you can get away with putting valve stem seals on. Most decent auto parts suppliers can help you with them. You can do it without tearing down the heads if you get one of those spark plug shaped adaptors that allow you to hook an airline to pressurize each cylinder so the valve won't drop when you take off the spring and retainer to install the stem seal.

streets, you have a really twisted sense of humor. Also, before you assume its the valves, check for the vacuum lead to the choke. As you lose vacum while shifing, the choke plate can drop. If the line is leaking to start with, it may be closing it off completly. Just a thought.