The International Cessna 170 Association

It’s a common discussion…comparing auto engines and aero engines… The auto engines supposedly are “hardier” in the minds of many.
But my O-300 was majored in the early ‘80s…but not put into service until ‘97. 25 years later it now has almost 1200 hrs….. at 100mph that would be about 120K miles.

Our C-145/O-300 (hp/cu-in) engines claim 145 hp at 2700 RPM.

My 1983 Mercury Grand Marquis was a 30-year newer engineered design…basically a re-badged Lincoln Town Car…. and had a 302 cu in V8…. which claimed 130 HP….. It first failed at 30K miles…(failed valve-train)….then again at 70K…(failed cam gear and timing chain)….. and then it was sold fairly inexpensively after only 7 years of family-service.

My 75-year-old C-170 with a 3/4-worn-out engine is worth between two and three times what that car cost new. (When the O-300 was majored, it was done using rebuilt cylinders…Each of which have been replaced with new Superior Cyls at some point over the last thousand hours.)

I used to have a cleveland 351 v8 in my race car and found the rocker gear and push rods the achilles heel. especially over 6500 rpm. I have kept as trophy’s a number of shattered pushrods . So my question is “are you over revving the engine ? . The windsor V8 also had an issue with the valve train.
Ford produces a “4V” heads and with titanium block rocker system will make your engine bullet proof. Could I persuade you to fit a 1150CFM 4 barrel, double pumper carb as that will smooth things out.

The “valve train” comment was a simplified description of failed hydraulic lifters (due to internal coolant leaks which created “sludge” that contaminated the lifters.) It was not over-revved… the car was not raced…it was reasonably-driven mostly “in town”….the model was what you likely call an “estate car”…. what we Yanks call a “staion-wagon”.

The point I was attempting to make was that “modern” Auto engines…while very reliable and common…. are not always as “bullet proof” or more powerful ….than one of the older aero-engine designs we often think is underpowered for it’s displacement. In actual fact, our 6-cylinder 300 cu in C145/O300 engine puts out about the same HP as that 302 cu in auto V8 did….(at a much lower RPM than the V8).

The C145/O300 is not underpowered for it’s displacement. But it is asked to do a lot if a 170/172 is expected to carry 4 “modern” adults and full fuel off a high density-altitude short field. When it’s considered the damands which are often placed upon it…. This engine is pretty admirable for a century-old design….running on tractor magnetos.