82 SC 3.2 Rebuild Smoking Mystery

[Kman]

Hello all,
I turn to you for diagnostic help:
Bought a 82 SC Targa with 120,000 tight motor with good compression and smooth running that did NOT have a pressure relief valve on the airbox (I did not know of the necessity at the time).

Backfire = Airbox Crack - Little screw freed to get sucked past intake into cylinder - screw embedded into piston - piston slams into valve - (get the picture). I decided to do a bottom up rebuild (not the best usage of budget).

Rebuild to 3.2 to be done by reputable mechanic in San Francisco with me acting as assistant / go-fer.

From day one upon starting (when cold) a puff of oil smoke. This "puff" was rather large.. more a cloud. I assumed it was a matter of everything getting seated and such so I proceeded to put about 10,000 miles on the rebuilt motor. The smoke did not go away. In fact, it had gotten a bit worse. Finally, the smoke persisted beyond the initial 'start up" and a trail of smoke followed me as I drove to my mechanics. After about 2 miles, the smoke stopped.

I was not present for the leak-down test. It was performed cold (never got a good reason why) and the result was 3%. Even though it was at nearly race tolerance, my mechanic pulled the motor and tore apart the top end. Number two cylinder was oil-moist. We pulled the cylinder and it turned out that the rings were installed with the gap at the bottom - opposite, as they should have been. YES! I thought we found the problem. Motor reassembled, back on the road and IT'S STILL SMOKING!! It smokes at start up and not just a puff. A cloud! One other thing - all the pistons had a pretty good layer of carbon covering them. It was removed. I've never pulled apart an engine with such little mileage on it, so I have no idea if this is normal.

Any ideas - advice or input would be most helpful. I'm at my wits end here. All I want to do is get my car back on the road. Any expert diagnostician in the San Francisco Bay area to refer?

TIA -
Kman -

[Thomas Owen]

Here is what I think based on several 911 rebuilds: If the smoke 'goes away' and you get a startup 'cloud' you still have something wrong in the guides/valve stem/valve stem seal area. On engines I have rebuilt with a worn or defective top end, you could pull the intake and look down onto the intake valves and see the oil sitting there on a closed valve, just waiting for the next startup. As far as the rings go, my opinion is that if your mechanic thought the problem was due to rings being 180 degrees from where they were supposed to be, I would get a new mechanic. Why? Because the rings do turn with time. The leakdown tells you nothing about the symptoms you are observing, it is most probably in the valve train in the form of a cracked guide or worn stem.
Good luck.

[Leland Pate]

WHo did your valve work when you did the rebuild?
Is there a chance that one of the the number 2 valve guides was improperly installed?

Where did you get the P/Cs you used? Were they new/refurbished etc?

[Kman]

towen - thanks for the reply, gives me a few paths to follow.

Leland - Good queston about the valve work. It was done by a shop my mechanic "always" used. The pistons were new, Mahle. Purchased by the mechanic. Humm, noticing a pattern here...

[makaio]

What's the name of your wrench in the SF area?

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Matt Chamblin
78 911 SC

[Early_S_Man]

K,

You say the pistons were replaced, but what about the cylinders? If they were reused, what kind of treatment or preparation was done to them, and what brand of rings were used in them?

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Warren Hall
1973 911S Targa

[Kurt B]

My engine is very noisy and tappy, but has never smoked so much as one puff..not on start up or ever...should I assume someone give it a top end rebuild along the line somewhere especially since it has almost 160k miles?

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Kurt B
1984 Carrera Cabriolet
911 Page
carrera_cabriolet@yahoo.com