Hangar 9 J-3 Piper Cub Assembly Manual page 23

Section 8: Installing The Engine
5. Rest the fuselage on its side with the right side of the
fuselage facing up. Place the motor mount plates on the
motor mount as shown in the picture below.
6. Set the engine on the motor mount plates and align the
plates to properly line up with the engine flanges. The
distance from the face of the prop hub to the firewall
should be 4-1/4" inches. Move the engine fore or aft until
this distance is achieved.
7. With the engine plates properly aligned and the prop hub
to firewall distance at 4-1/4" mark the location for the
mount holes (4 places). Four holes (one in each corner of
the engine plates) will attach the plates to the engine
mount, while the other four holes attach the engine to the
engine plates. A sharp pencil is recommended to mark
the correct position.
8. Remove the engine and mount plates. Now drill four 1/8"
diameter holes at the points on the engine mounting
plates marked in Step 7.
9. Mount the engine plates to the engine mount with four
screws, eight washers and four locknuts.
10. Now place the engine back on the engine plates. Again
measure the distance from the firewall to the prop hub and
adjust the engine position until a distance of 4-1/4" is
achieved.
CONTINUED
23