GREAT PLANES Gee Bee Instruction Manual page 15

Even with the extension it will be necessary to make a small
clearance opening in the bottom of the fuselage to allow
clearance between the muffler and the fuselage. Depending
on the brand of engine used, you may have to change the
position of this clearance hole. Again, depending on the
engine you use you may or may not have to cut the cowl for
a standard muffler to clear. You may want to consider using
a "Pitts" style muffler.
As you can see there are some variables that you will have
to work with depending on the engine you choose. The
O.S. 1.20 four-stroke is our engine of choice because of
how neatly it fits inside of the cowl. Before proceeding with
installing the engine mount and engine, be sure you spend
some time looking closely at how your engine will fit into
the cowl and how well the muffler exits the fuselage.
1. Locate the left and right halves of the engine mount.
Remove the molded spreaders, leaving the engine mount
to look like the photograph. Be sure the two halves fit
together smoothly.
The next few steps are going to cover installing the engine
onto the motor mount. You may have assembled other kits
where you installed the mount to the fuselage first. By
mounting the engine to the mount first you can easily
position the engine and muffler on the firewall as needed.
2. Position your engine onto the engine mount. Position
the engine on the mount so that the distance from the back
of the engine mount to the front of the engine thrust washer
is 6" [152mm].
3. Using the engine as a guide, locate the four holes for
the engine bolts. This is easily accomplished with a Great
Planes Dead Center Tool (GPMR8130). Drill four #29 or
9/64" [3.6mm] holes in the mount. Then, use an 8-32 tap to
thread the holes.
4. Use four 8-32 x 1" [8-32 x 25mm] socket head cap
screws, four #8 lock washers, four #8 flat washers and
Thread-Lock to install the engine onto the mount.
5. Locate the fiberglass fuselage. On the firewall you will
find reference marks for the engine mount. Using a felt tip pen,
draw over the reference marks and extend them further out
onto the fuselage. This will assist you in mounting the engine.
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