Crankcase - Lycoming IO-390-D Series Installation And Operation Manual

IO-390-D Series Engine Installation and Operation Manual

Crankcase

The crankcase (Figure 3) is made up of two cast halves attached by a series of thru-studs, bolts and
nuts.
The crankcase forms the bearings for the camshaft. The camshaft operates the tappets which control
opening and closing of the intake and exhaust valves. For front propeller governor models the
camshaft has an integral spur gear that drives the propeller governor output shaft.
The main bearing bores are machined for precision-type main bearing inserts. The crankshaft main-
bearings are pairs of inserts installed in the crankcase at each journal.
The crankshaft (Figure 4) is within the crankcase. The crankshaft has journals and counterweights.
The counterweights decrease torsional vibrations as the crankshaft turns to operate the propeller.
Oil is supplied through the propeller flange for a single-acting controllable pitch propeller.
Four oil nozzles supply oil for internal piston cooling
Figure 3
Crankcase
Figure 4
Crankshaft
System Description © 2020 Avco Corporation. All Rights Reserved
Page 2 March 2020