Fuselage: Forward mid fuselage side structure. Firewall wasn't straight. Now it is.

When the upper longerons are placed against the firewall (page 29-08), the upper engine mounts should lay flush against the firewall gussets F-1401L. The right side clearly did not. Only the lower inside corner of the engine mount made contact with the gusset. This meant that the engine mount wasn't straight relative to the firewall.

Looking from top, left on left and right on right.

Further inspection revealed that the two aluminum angles, F-01401D and F-01401J, that compose the upper C-channel of the firewall have a curve in them. They are not straight. A straight edge laid across the top of the firewall illustrates this curvature (convex with respect to the aft side).

A call to Van's yielded the suggestion that I use a bottle jack and 2x4s to take out the bow.  I lack the skills to make that happen (in fact, it's worth questioning whether I have any skills at all).  It turns out, another  builder of an RV-14A that I'm in touch with is a shop-master. He owns and operates a very well-equipped machine shop.  He very kindly came up with the following contraption to straighten the upper firewall C-channel.

It's a steel support bar with three points of contact on the firewall. Two are the upper engine bolt holes with Delron standoffs. The center point is just a thick threaded screw with its head cut off, placed in a Delron sleeve to prevent marring of the C-channel's surface. As that screw is advanced, it pushes the center of the C-channel, whilst the outside screws hold the C channel's edges back. Let's call this device the Clifflatron.  Here it is in place ready to do its dirty deed.

It took this much bow, about an inch at the center, to take out the firewall curvature!  And yes, this was not an easy to task to do only because I was waiting for the explosion of overstressed parts. 

And now the firewall is straight.  Left is pre-straightened. Right is post-straightened.

One would think that the issue with the engine mount is solved now that the firewall is straight.  It wasn't.  In fact, there was no change!  Left is pre-straightened. Right is post-straightened.  I can't explain it.

When the temporary 3/8” bolt is tightened, the gusset and angles deform a little bit and ultimately conform to the engine mount, closing the gap.  I've accepted this and moved on with the build.