Engine Mount to Firewall Fit

My engine mount does not line up with the holes in the Firewall (9 QB). It is out on one hole about 3/32! Has anyone had this problem. I also posted in the 9 Forum. Thx. Rolly

Don't know much about a QB9, but on my super slow build 4 the plans had me drill 3/16 holes (might have been 1/4, I don't remember) through the firewall until the engine mount came. Then I used hardware store 3/16 bolts to attach the engine mount. Once everything was tightened up, I removed one bolt at a time and used the engine mount as a drill guide for the 3/8 holes. I deliberately dulled the sides of the 3/8 drill for this operation. This method takes care of small misalignments of the holes. Sorry I don't have specific QB9 info.

Steve Zicree
Finally riveted my canopy structure together today. Whew!

The 7 and 9 are the same. Drill the two center holes first and install the mount using just those two bolts. Align the mount to the other 4 outer holes and drill them using the mount as a drill guide. Install the bolts as the holes are drilled to maintain alignment. Use undersize bolts to help maintain position while drilling, if necessary.

Installing the engine mount is easiest while the fuselage is in the earlier stages of construction. Once the forward deck is installed, it gets harder.

Hope this helps,

Roberta