Hi Victor, With all due respect to Sajeev's assessment, I'd hold off on assuming that your problem is caused by excessive blowby from a worn engine. The valve cover gasket and oil cap gasket would exhibit oil seepage from excess blowby before much else, and the air cleaner housing would have heavy oil residue inside as well. I'd be more inclined to say that you are experiencing gaskets deteriorating due to age. Elimination of the PCV system will throw off carb mixture and your '79 may have sealed mixture adjustment screws. And you'll end up with oil ooze coming from that breather cap. If the little leak you describe really bothers you, find an ASE certified shop to perform a compression test and leakdown test. That is the only way to truly determine the mechanical condition of your engine internals. I would suspect you could get by with disassembly, cleaning and reassembly with fresh gaskets & seals, considering your meticulous maintenance habits. Either way, get a professional assessment and then decide on how much you are willing to spend on your ride. This comes from a retired licensed mechanic /ASE Master tech (we have licensing for mechanics in Canada) with over 30 years experience.
Hi Sajeev; Considering the trucks age and mileage, the first thing I'd do is change to a 15w40 oil and see if that doesn't fix the problem. High mileage engines do tend to leak a bit more and also have greater clearances due to wear etc. A little heavier oil can help with the small leaks and also give better lubrication when the engine gets warmed up.
Oil should be replaced when it meets certain criteria regarding contamination, dilution and deterioration of additives. Oil does NOT meaningfully deteriorate while sitting idly in the crankcase of your motor, so the "so many months" guidelines are really only something easier for busy urban drivers to remember than the mileage and degree of hard service by the motor. Your weekly 15 mile outings (IF they include enough medium-speed driving to get the engine completely warmed up) could go on for five or six years before you hit the recommended change mileage for your truck. More frequent changes are perhaps comforting to the owner but really a waste of effort, oil and $$.
Victor, check the end play of your crank. If your able, grab the crank pulley with both hands and pull/ push the crank pulley. If your seeing enough end play to hear an audible click in the bottom end that could cause oil to pass your rear seal journal. A worn thrust bearing would be a root cause for that type of leak. 150K and a drop or two and no significant loss of oil? I don't know if I'd be to concerned.
Regarding the video, Broken piston. Cause, extended periods of wide open throttle and detonation. Or, engine was not manufactured with the type of piston that would withstand the combustion pressures plus heat of turbo charging. That would be forged pistons. With the bean counters at GM I believe cast pistons could be possible especially at such low miles. I would not be surprised.
It could be blow by but please do a compression test. If you have blow by you will be down on compression in that engine.
Do a dry test then do a wet test with a little oil in the cylinder and see if it increases the compression.
This will show if is wear. The above example may be more a broken ring or piston.
My gut is telling me you may have more gasket and seal leaks than blow by. 41 years on an old engine from an era that had a lot of leaking engines.
We had a truck,like this in the early 80’s and it leaked even back then.
What you have is a incredibly rare truck that is not worth a ton but if in good shape it is not expensive to pull and refresh an engine like this. I know a truck like this is a rare sight where I live and I have many memories of it.
It was an Orkin truck that had crashed and was rebuilt into a kind of California hauler. We often rode three to the cab but the guy in the middle had to shift.