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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: tmedic on October 05, 2010, 11:07:03 am
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I have a 87 Custom Deluxe. It was doing great until I towed a small trailer. When I was backing the trailer white smoke started coming out both exhaust pipes. Oil level is fine. Truck has a 305 TBI. The first time it did this I blew it off. The second it was a little more smoke and it blew out a big puff when I put the truck in drive but then cleared up. I also noticed a 5 mpg drop in my fuel economy at the same time. Any idea's would be appreciated.
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Sounds like blow by. That's what happened to me with my 350 tbi. I was blowing oil out of the valve covers and eventually the exhaust started smoking pretty bad. How old is the engine?
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Original engine. I did about 3 months ago switch to a true duel exhaust. If that makes any diff.
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Did you check your coolant level/condition?
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Well it might be due for an overhaul if it gets much worse... My 305 tbi did that but only on start-up. I've since put in a 350 tbi that I blew the rings in which is getting replaced as of now.
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Engine coolant levels and condition are good. Oil levels and condition are good too. By overhaul what do you mean? I'm guessing more than the typical fluide change and plug/wire change.
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Try removing the pcv valve and the pcv vent hose from the valve covers and start it up. If a significant amount of smoke comes out of the valve covers then its worn rings. Of course a cylinder leakdown test would be the best thing.
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Just tried that. Smoke did come out about half the amount you'd get from blowing out a match.
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Sounds like the seals in the heads are on their way out. Did you do a leakdown test?
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No I don't know what a leak down test is.