Aircraft Engine Historical Society Members Only

LeBlond 7D Restoration
by Mike Grimes
Published 20170413

This engine, a 90 hp LeBlond 7D, s/n 563, was removed from 1929 St. Louis Cardinal NC559N, s/n 113, when the aircraft was dismantled for restoration. The owner turned the restoration process over to two local mechanics that performed the airframe restoration. As part of the restoration process they dismantled the engine and sent all parts out for cleaning and inspection. When the engine parts were returned they had a crankshaft, master rod and one piston with RED tags attached due to cracks! Not having a source for parts they simply reassembled the engine as a static display, without rings or gaskets, and mounted it on the airframe.

The 7D is an early LeBlond engine that has only two main bearings and cast iron cylinders cast in one piece. Being a two main bearing engine, there is no way for the precessional loads from the propeller to be restrained other than through the entire crankshaft to the rear main bearing. This causes the crankshaft to flex and eventually crack. It’s not a matter of if, but a matter of when.


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