My 1952 B model has had two major overhauls in it's 50 year existence - first in 1960 at about 700 hours and in 1974 at 1,450.
Here it is 2002 and 2,250 hours airframe and engine (still with the powerplant it was delivered with.) I've been fighting cylinders one at a time since I bought the thing in January 2000...leaking exhaust valves, worn guides, worn-out rocker arm towers and such. The only two cylinders that haven't been off the engine since 1974 have egg-shaped wear in the rocker arm towers (number one, with no bushings, obviously first run) and a missing bushing on the number six. That's it - I bought six brand new Superior jugs, with the idea of topping it.
For this job in these parts, there is no choice as far as I'm concerned. Ray Stillwell has been an A & P since 1956. He specializes in re-builds, and has done many O-300s in his day. He did the 150 Franklin on my Stinson, and does top-notch work.
So after the cylinders are off, I mention this might be a good time to pull the rear case and the sump, because the oil leaks are getting pretty bad.
He gives me one of his looks, and I know what is coming next! I beat him to it..."well, the only thing left on the mounts are the two cases halves and the crank and camshaft; how much do you think it would be to just go ahead and major it? He comes up with a very reasonable number. I think about it overnight and then tell him to go ahead.
It's probably overkill on my part - oil pressure in cruise is 45 psi and 30 at idle. If the sump and rear case weren't leaking so bad, I probably would have stuck to the original plan. But the only real downside was the money; VERY real- but I do fly my airplane IFR and night VFR. Plus 28 years IS a long time...this is from a guy who was flying a 1946 Stinson around on an engine that had NEVER been re-built since new
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If you guys are interested, I'll keep you posted as events warrant...Russ Farris