Great Planes Pitts Special 1/3 Scale ARF MonoKote - GPMA1218 - Manual (Page 23)

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2. After removing the spreader bars from both engine
mount halves, fit the two halves together using the engine
to space the width properly. Notice that when you find the
proper width for your engine, the tick marks on the two
halves of the engine mount will no longer line up with each
other. Measure the distance between the two tick marks and
mark the center location between these tick marks. This
location will be used to properly align the engine mount with
the firewall markings.
Being careful not to move the width of the engine mount,
position the engine mount onto the firewall using the tick
marks and the marks you just made on all four sides of the
mount to align it with the horizontal and vertical lines on the
firewall. Mark the location of the holes with a Dead Center
Hole Locator (GPMR8130).
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3. Drill four 7/32" (5.6mm) holes through the firewall at the
marks. Apply 30-minute epoxy to the four 8-32 blind nuts,
being careful not to get the glue into the threads and place
them into the holes on the back of the firewall. Attach the
engine mount to the firewall with four 8-32 x 1" (25mm)
socket head cap screws and #8 flat washers. This will draw
the blind nuts into the back of the firewall. Allow the epoxy
to cure.
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4. Position the engine on the mount so the engine drive
washer is 6-1/2" (165mm) from the firewall. This will provide
the correct clearance between the spinner and the cowl.
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5. Using your Dead Center Hole Locator again, mark the
hole locations on the engine mount. Drill #29 (or 9/64")
holes through the engine mount at the marks you made,
then tap 8-32 threads into the holes. Mount the engine to
the mount with four 8-32 x 3/4" Socket Head Cap Screws
and #8 washers.
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6. Test fit the muffler to be used on your engine. The O.S.
1.60 FX (OSMG0661) is shown in this manual. Bisson
Custom Mufflers produce a Pitts Style Muffler (BISG4116)
that is designed specially to fit this engine and is shown in
the photo above.
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