Mystery fastener hole on heater box

[MikeB]

The hole on the far right lines up with a hole in the firewall that protrudes only into the blower area. That means I can't put a nut on the back. How does the box attach? Does it use a nylon retainer like those used to secure door panels?

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[yevgenievich]

If I remember correctly there is a bolt that has a gripping washer keeping it from falling out.

 

[chengny]

The hole on the far right lines up with a hole in the firewall that protrudes only into the blower area. That means I can't put a nut on the back. How does the box attach? Does it use a nylon retainer like those used to secure door panels?

The fastener used in that hole is supposed to be a self-tapping type bolt. It threads right into the sheet steel of the firewall -you shouldn't need a nut on the other side.

 

[MikeB]

Thanks guys. I woke up this morning and remembered there was a large sheet metal screw there! If the hole is worn out, I'll epoxy a 1/4" bolt from the inside with an external star washer under the head. Poor man's stud!

 

[chengny]

Or it might be easier to just go up to the next size self-tappper.

 

[Stepside81]

On my '81 it takes a 10mm bolt. Firewall is threaded to accept bolt.

 

[MikeB]

I ended up installing 5/16 bolt and snugged it in place using a thin nut, effectively ending up with a stud for the heater box hole. Since there is 1/4" "pin" near the hole in the heater box (and several more around the perimeter) to allow for the thickness of the firewall pad, the nut does not interfere with the sealing, if that makes sense. Should have taken pictures.

 

[MikeB]

On my '81 it takes a 10mm bolt. Firewall is threaded to accept bolt.

6mm bolt with 10mm hex head. I think that's what mine was, but hole was stripped. I need to take more pictures during disassembly next time.