Reliability of O-300

Several years ago I bought a '61 straight back for my wife and was shy about
the 0-300. Since then I've grown to love it. It does run smooth and all her
instructors rave about it. For some reason the plane is unusually quick also.
Climb is average.
1. What kind of fuel burn do you consistently get with an O-300? Is
the generally reported 105 KIAS @ 8 GPH true?
At 105 KIAS I actually think it's a little better, maybe 7GPH.

2. Does the autogas STC help reduce the problem with valve sticking?
If you have the STC, do you generally burn a mix?
Got the STC and been burning pure regular. It runs noticably better (and
considerably cheaper) but we are agressive about applying carb heat even though
I have never felt a trace of ice. The guy who sold it to me said it never saw
auto gas. Used a lot of oil so I took the top end apart. Only one valve was
slightly close to snug but 3 of 6 cylinders had one or more frozen rings from
carbon and goo. The cylinders mic-ed up within spec. (An A&P told me the older
cylinders were great but the new ones are too soft. How do I know?) Put new
rings on and now the engine is running sweet. This was the first thing done to
it in 1800 hours.

3.In general, has your experience led you to expect to have to do a
top overhaul about halfway through the TBO period? What are the
ballpark costs of such an operation.
The ring job, 1 wrist pin, 2 valve guides and a gasket set cost me a tick over
$400.

4. In your opinion, would it be worth it to pay the premium to buy an
new 172 equipped with the O-320E2D?
My biggest bitch is that those Continentals seem impossible to stop from
leaking oil. The Lyc. in my other plane is always dry.

5. Besides the valve guide and cylinder problems (often attributed to
running on 100 LL), are there any other major problems that would make
this an undesireable aircraft?

Thanks for the help,

Cap


Jim