Yes...what you describe addresses the challenges of running and maintaining a motor with 320,000 miles on it....there will be wear which results in various characteristics that need to be "managed" prior to reaching the point where you finally decide that it is time to remove the head and do a valve job. With my car, it has always been maintained very well....I have all records since first owner. So, while I have low compression (240 psi) in a couple of cylinders, the car does run well. I know that the valve guides are a little worn, but there is almost no blowby (no smoke from oil filler opening when engine is running), so valve guide wear is very minimal. Also, there is very little smoke from tailpipe (unless really stomping on the accelerator), so engine performance is good.

What I would really like to do is get another 100K miles out of the car without doing a valve job. My strategy is this...let me know your thoughts...

1) Worn valve guides will result in wobble at the valve stem and the valve stem seal, allowing oil to pass by the seal into the combustion chamber. But also consider that the current valve stem seals are original and probably brittle, affording a poor seal as the valve stem wobbles. I will install new valve stem seals to counter this and minimize oil leakage into combustion chamber. Valve guide wear is very minimal as evidenced by very little or no blowby, so new seals will probably minimize oil leakage. I have a new set of valve springs...I will might as well put these in when I install valve stem seals.
2) New valve stem seals will minimize leakage of oil into combustion chamber and will therefore minimize carbonizing of the valve seats. Since I assume valves and valve seats are a little worn (due to high mileage), I should adjust valve clearances more frequently than normal (three times per year, every 5K miles?), and I should adjust valve clearances a little more open than spec. to allow the valves to seat as well as they can (they will be allowed to bang themselves in if clearances are kept open)...new valve springs may help the valves bang in and seat as well as they can, but this benefit will probably be very minimal (old springs are probably just fine).
3) Because oil changes have always been done religiously (every 3 to 5k miles), I don't think there are major problems with lower end (rings are probably good), but as a preventative maintenance, I will use an oil additive with every oil change....NOT those products with some kind of leak stop crap, but something like Lucas products that say it is for freeing rings, upper cylinder lubricant, etc.

Thats it...I will just monitor compression each year, and hope for the best. If compression goes down too much, it will probably be the result of bad valves. If it gets to the point where I can't reliably start the car during cold winters, then I will need to do a valve job. (I would first do a leak down test to make sure lower end is good....if not, then I would have a real decision to make...I don't thing I want to get into replacing the rings...I have never done that, and I assume it is a big job...especially with no garage...I am a driveway mechanic).

Thanks,

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)