Fire Caulk
 

Is it acceptable to use a plastic snap busing and fire caulking for the wirer's penetrating the firewall. I am building a 8 and were the planes call to go thru I don't think I can get a metal shield between the side skin and center of hole?

passthrough
 

Vans says the snap bushing and caulk with silicone method is OK. It is done that way on many certified planes as well, however, I find it a splendid place to upgrade. I used a cable clamp (Cable Safe) on my firewall passthroughs. Tight, and flame resistant, but also stabilizes the cable sheath to allow a predetermined amount of flex between your stationary firewall and moving engine. Very hard to achieve this without anchoring the cable sheath at the firewall.

YMMV,
Chris

OOPS
 

Sorry, misread your post. If you are using a passthrough for wiring, it is established practice to silicone a wiring bundle.

Regards,
Chris