9
Next mark your firewall with center lines. Label the firewall “Top” and “front“
with a pencil. Now measure & mark the last line as shown.
The line that runs horizontally can be moved to accommodate your particular en-
gine. However, the centerline of the crankshaft should be placed as close as possi-
ble to the wing line extended. We are now ready to mark and drill our firewall for
our engine. Take the engine mount pattern you made in the last step and place it
over the firewall so that the center marks of the engine pattern line up with the new
centering mark on the firewall. Rotate until vertical. Use an ice pick or an awl to
push though the center of each of the 4 engine mounting holes. Make sure you
make the hole big enough to find later. When done, drill the firewall through each
awl mark with the appropriate size bit for your engine mounting bolts. (10-32
hardened, socket head bolts and blind nuts will do nicely) Also use a hole saw or
jig saw to cut out the center until your carburetor passes through easily.
We are now ready to epoxy the firewall into the engine box. BE SURE TO PUT
THE TOP AT THE TOP AND THE FRONT TO THE FRONT – as labeled in the
previous step. Wipe away excess epoxy. A large blob in the wrong place will pre-
The ¼” off-
set is to
counteract
t h e r i g h t
thrust. This
w i l l b r i n g
t h e p r o p
shaft back
to the cen-
ter of the
cowl as it
exits.
