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Old 04-04-2006, 12:53 PM
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new engine is smoking

I have a completely rebuilt dodge 383 magnum with odd oil smoking problem.
It's been apart twice in an attempt to find the problem. I'm baffled the engine runs fine but if it idle's for any length of time (5 min) it starts smoking badly.
You can drive at freeway speeds for hours with no real oil consumption. It has 2000 miles on it and seems unchanged since new. A trip down long hills in low gear produces no smoke when you step on the gas. It has all umbrella valve seals to eliminate the positive style seals. Oddly two plugs get oily if you let it idle for 30 mins and they are 5 and 6 which are on opposite banks and only share a crank throw. It has Keith Black utectic pistons and street total seal gapless rings. On the tear down when this problem began the rings were all double checked for endgap in there respective bores and piston/bore clearance
verified. The machinist examined each piston for defects and found none.
I don't want to tear it down without some further ideas of things to check.

Potts
69 coronet 383

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Old 04-04-2006, 01:02 PM
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do a compression check and leakdown test... it could be your rings are failing to seat.

Are you running a PCV valve? if you are and theres no baffle in the valve cover then you could be sucking oil into the carb causing it to smoke like that too.
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Old 04-04-2006, 01:22 PM
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The compression test shows all within 5 % and leakdown on all is very low typical of gapless rings. The pcv has a 060 restriction in the line. I've completely plugged it with no change in the smoke. I have tried the old repeated full throttle passes to seat the rings to no avail. The rings were of course moly and the bores were machine honed to the finer finish that requires. It had new complete guides installed in the heads and I tore them down to measure the guides in case something there had failed but they measured out fine.

In all the engines I've built this one has me stumped

potts
69 coronet 383
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Old 04-04-2006, 01:31 PM
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are the intake bolts tight? and how do the intake gaskets look?

Also, if you have a modulator for your transmission the diaphram may be split allowing transmission fluid to be sucked into the carb causing it to smoke.

other then that i'd have to say the heads may be warpped or bad head gaskets
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Old 04-04-2006, 01:37 PM
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It`s funny, I just finished my rebuild, a 96 Chevy vortec 350. with KB pistons, vortec heads, comp roller cam, edelbrock performer intake, super comp headers, moly rings gapped correctly. it smoked like a steam train, especially at idle. it pulled 16 inches of vacuum, had good power. Oil signs showed up on the back plugs, very little on the front. I noticed it got hot also very quickly, but didn`t overheat, it also showed signs it was lean, but didn`t have a lean surge. I was going to pop the valve covers and investigate by popping some valve springs, but I decided to check the intake first. When I assembled the engine I used sealant on the head, but none on the intake, vortec intakes have a sealing rail built in, so I didn`t think it needed any sealer. when I removed the intake there was oil everywhere, all over the intake and all in the ports, I shined a flashlight in the head ports and there was oil everywhere, and a nice puddle on the back of each valve. the car only smoked at idle and from take offs, other than that it didn`t smoke. I cleaned the intake and sealed it with RVT, afterwards it smoked about a hour, since it hasn`t smoked any and the quick temp jump was eliminated.
Why it showed no signs of a intake leak was I believe to be due to the oil, the oil was acting as a sealer, so it was a controlled vacuum leak. I had a vehicle years ago with a intake leak and it didn`t smoke at all, but it had a hesitation in the carb I could never get out.
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Old 04-04-2006, 02:13 PM
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The heads were ground when they were machined. The intake and head gaskets are the steel shim design
The manifold is a natural air gap design with the tin tray being part of the intake gasket. The bolts are tight and were installed with sealer etc but of course a leak from the lifter valley could end up in an intake port. I don't recall any sign that the manifold had been machined on the sealing faces but it came to me from a separate source so anything is possible. I have tried the carb cleaner treatment around the manifold for vac leaks. If your suggesting it is leaking from the lifter valley into the ports any easy tests to prove this before I pull it apart again?

Potts
69 coronet 383
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Old 04-04-2006, 02:18 PM
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not really any easy test. pull the intake and shine a flashlight down into the ports to see if theres oil pooling in them. if you had your heads shaved and not your intake that means the contacting surfaces are mis-alligned and that could be part, or all, of the problem.

So, pull the intake and look for signs of oil being sucked into the runners.
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Old 04-04-2006, 02:27 PM
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I'll give that a try. The machinist says that the heads were only cut enough to clean them up so the alignment should okay but the manifold itself may be warped enough to produce a leak.

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potts
69 coronet 383
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