by bgsengine » Mon Feb 08, 2016 1:08 pm
the "M" in HM70 refers to "Medium Frame" tecumseh engine - as you noted there are some external differences, and I believe the valves and internal parts are different - main thing it refers to would be the fact of the cylinder liner (Cast Iron liner) - the HH70 will be a "heavy frame" engine and the block is all cast iron as long as the engine bolts in , crank dimensions are correct, etc it should not matter if you are replacing the whole engine.
How poor are they who have not patience. What wound did ever heal, but by degrees? - Iago (Othello Act II, Scene 3)