by ffkiwi » Sun Oct 12, 2014 8:49 pm
Yes-they are the same.....BUT. (there's always a but...!) it depends on which model Frog 150 you use-the later ones-designated the '150R' had a much shorter piston than earlier models (and plenty of SPI as a result-which is largely where the extra performance came from-with a slight bonus from the lighter piston which resulted)-the July 1956 Aeromodeller engine test notes that the 149 uses the same cylinder piston and rod......but this of course would refer to the 150 model extant at the time-which if memory serves would have been the 150 Mk2. Whilst I'm sure the later P/L will fit, I have no idea whether the performance would be the same, better or worse than the original. [I have just checked my two Vibramatics-they have no SPI whatsoever, whereas all my later model 150s do..apart from my original silver head first model one.
You're in Australia-why not get Jon Fletcher to make you a new piston for the original liner.................?
ChrisM
'ffkiwi'