Blue smoke!

[Sunroof]

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 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 very noisy) or if its a simple mixture adjustment, but my gut tells me its the old valve guides or bad rings. Either way, its going to be costly!! So, with this information, I am asking the knowledgeable reader, how does one test for or determine the cause (compression test?) for such a problem?

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 add a can of Bardol or Marvel Mystery Oil and call it done?!

Any feedback is well appreciated

Bob
1973.5T

[Speedy Squirrel]

You can easily do a compression check to see how the rings and valves are sealing, but it is almost certainly guides at that mileage, and considering the valves are noisey. Maybe the spraybar became plugged, which brings us to the additives you mentioned. You don’t want to take any risks plugging anything with those products.