Hello,
My snow thrower started making a knock sound under hard load recently... it is only 2 years old very little use... I think perhaps the head bolts are loose... no visible exhaust leaks... and every time I heard the knock I shut it down... any thoughts and anyone know the torque specs for head bolts? Thanks :)

Hi,
Doubtful that it is head bolts. "Under heavy load" seems to indicate it is something to do externally to the engine, assuming that the oil level is correct.
Peace,
Clarke