Rivet firewall or engine mount first?

[toolmanmike]

I finally got my finish kit and am ready to mount my engine mount but noticed the firewall flange will be almost impossible to rivet once the engine mount is installed. Plans are not very clear here on what to do. I can not space out my skybolt fasteners until the engine mount is at least partially located and I locate the “split for the cowling. But, if I install the engine mount first, I can not get to the back of the firewall flange. Should I rivet it now and drill out later where needed? Should I guess at the spacing of the skybolts and install ahead of the engine mount?

what have you all done? Can’t actually find any mention of riveting the firewall in the plans at all!?
toolman

 

[PaulvS]

I finally got my finish kit and am ready to mount my engine mount but noticed the firewall flange will be almost impossible to rivet once the engine mount is installed. Plans are not very clear here on what to do. I can not space out my skybolt fasteners until the engine mount is at least partially located and I locate the “split for the cowling. But, if I install the engine mount first, I can not get to the back of the firewall flange. Should I rivet it now and drill out later where needed? Should I guess at the spacing of the skybolts and install ahead of the engine mount?

what have you all done? Can’t actually find any mention of riveting the firewall in the plans at all!?
toolman

Install the engine mount temporarily in order to fit the skybolt fasteners, as needed. It is relatively easy to take the mount off, if ordinary (non-locking) nuts are used during initial fitting.
You are correct in that some rivets cannot be easily set once the engine mount is bolted on.