Hallo everyone,
I managed to drop the liner from my FP 40 and now its way out of round! Fortunately, Jim Thomerson came to the rescue and sent me a Tower 40 piston liner and conrod (Thanks Jim, what a kind gentleman you are). As I got to assembling the FP 40 with Jim's new bits, I got to wondering.
Perceived knowledge says that the FP 40 is almost certain to runaway after the first manoeuvre. Most posts that I have read seem to go along with this opinion, unless you use the Philly Fliers tune up. There are a few folk who say that the FP 40 is good out of the box. Apart from the Philly Fliers tune up, most other people resort to sending off the motor to a man who can fix it!
On the other hand, everyone including Jim, says that the Tower 40 is a real pussycat stunt motor, good straight out the box with no runaway! This is a bit odd as the Tower is an excellent clone of the FP 40, you can mix and match the parts and they all go together, no problem. The only tangible difference is that the Tower is ABC and the OS is ABN. is the difference in behaviour down to this? If it is then why does the ABC liner work and the ABN liner most times doesn't?
It may be that the difference in liners is a red herring. I know that the fabled OS quality is somewhat lacking in the later FP 40s. For example the crankshafts are not up to the Tower item (reported in some threads), also the deck height of the OS has varied surprisingly in the samples I have measured. I don't know about the Tower 40 as I have never had any to measure! Could the unpredictable behaviour of the OS be linked to this rather than the ABC / ABN difference?
The reason that I ask is I am wondering if my OS 40 with Tower 40 innards will behave like a typical OS or a typical Tower! The engine is now assembled but its too cold to go fly it and find out. I am getting a wimp, no flying with snow on the ground!
Regards,
Andrew.