Hello all,

OK, excuse the ignorance and "amateurism". What is the difference between the C-145 and the O-300 engines. A little history, differences in available accessories, performance, reliablility,etc would be nice.

Thanks for your input!

Macdon221

the 0-300-A is a C-145 they are diferent in name only the subsequent B&C models have minor changes and finally the D model has a 6 bolt crank flange and an engine driven vacume pump it obviously is the desireable one. but only for the vac pump they are all equaly dependable and use the same jugs.

It's my understanding that they are essentially the exact same engine, just a different model designation, as Continental changed their model name scheme in the mid-1950's. There are subtle differences in the O-300A, O-300B, etc I believe. I'd be interested in what those are as well so I can complete this page:

http://www.cessna170guide.org/wiki/Continental_C-145

Edit: Too late, beat by CCurie, former owner of my C-145

There are only detail differences between a C-145-2 and an O-300A. For all practical purposes they are identical engines. For the record the differences are:
1. The cylinders on the C-145 have bronze bushings for the spark plugs. The O-300's have heli-coils.
2. The pipe plugs at the forward end of the oil galleys are one size larger on the C-145
3. The C-145's have Bendix SF-6-12 or S6LN-21 magnetos. The O-300's have Bendix S6LN-21 or Slick Model 664 magnetos.
4. The later O-300's have a superior oil seal for the starter clutch.
5. The later O-300's have an alternator.
6. The C-145 has a splitter above the carburetor, in the oil sump, which is sheet steel, held in with two rivets. The O-300's have the splitter cast in integral.
7. The carburetor is a Marvel Shebler 10-3237 for a C-145 and a 10-4895 for an O-300. The numbers may be different but the carburetors are for all practical purposes, identical.
8. The camshafts are all p/n 530803 but the later ones have suffix such as -AN, -AT or -AU. These camshafts seem to perform well at higher rpm, the earlier camshafts might perform better in climb. There were some cast iron camshafts before 1950 but I doubt any of these are around anymore. The C-125 used a cast iron camshaft. It is important not to use a cast lifter on a cast camshaft, they require a steel lifter. Also, a steel camshaft (p/n 530803) requires a cast lifter body. (p/n 530851)
9. The C-145 lifter bodies don't have a circlip to hold the "guts" in the lifter, the O-300's do. This has caused all sorts of grief to guys that pull a cylinder and break a lifter, necessitating splitting the case to replace the lifter.
10. The C-145's have "wet studs" -- the cylinder studs are installed in tapped holes that go into the case and thus possibly leak oil. The O-300 castings are revised so the studs are in blind holes and can't possibly leak. (I have seen O-300's made before 1960 with the C-145 style case)
11. All C-145 and O-300 engines with a "D" in the serial number have a dampened crankshaft. Continental made a few C-145's in 1948 with undampened crankshafts, I doubt if any of these are still around.