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Join Date: Feb 2001
Location: South of the Mason-Dixon Line
Posts: 3,430
BLUE SMOKE......panic ensues!!

I own a 1973.5T 911 with the 2.4 engine coupled with the 915 tranny and fueled by CIS. I have owned it now going on 19 years. The engine had a total rebuild at 92,000 miles back in 1991. Today my odometer is reading 174,000 miles and the engine still pulls strong with no unusual noises while driving.

On start up ordinarily I will get some smoke (blue) that's lasts only a minute before it clears. I attribute that to the oil that accumulates when sitting awhile and expected from an older air cooled engine, BUT recently, I have noticed that the smoke coming from the exhaust (blue) is prolonged and when I drove it last (yesterday), at the stop lights I could see smoke out my rear view mirror. Panic of course ensues!!!!

It would be wonderful if all it took was a valve adjustment (the valves are extremely noisy) or if its a simple mixture adjustment, but my gut tells me its the old valve guides or bad rings. Could it be something simple since it feels engine performance is still excellent? So, with this information, I am asking the knowledgeable reader, how does one test for or determine the cause for such a problem? Or do they not know until they tear it down?

The second part of course is what can I expect to pay for a valve job on a 2.4L air cooled engine these days? Or do I just add a can of Bardol or Marvel Mystery Oil and call it done?!

Any feedback is well appreciated. I am going to continue to post to next find out what shops in Atlanta have the best reputations for doing such work on the older engines.

Old 09-16-2018, 07:45 AM
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Join Date: Nov 2008
Location: NY
Posts: 2,976
82,000 since the total rebuild. Any invoice on what the total rebuild consisted of? Did it have cylinders honed with new rings, new pistons and cylinders, new valves and guides?
Blue smoke could be oil leaking past rings, valve guides, valve seals, or over filled oil tank. Have you checked to see how much oil the car is losing over a given mileage? Have you pulled the spark plugs to see how they look? What do the valves and stems look like on the intake and exhaust?
Best way to check rings is leak down test. Only way I know of to check valves and guides is to remove and measure them. If the valves and guides are worn, I would not use additives to mask the problem. This could lead to a dropped valve down the road.
1973.5 T
Old 09-17-2018, 07:43 AM
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