Topic: Hole in firewall - what belongs there?

[cobrapatrol]

My Nov 64 SJ K-code fastback has a hole in the firewall approximately where the A/C hoses would go - pictured below. But, of course, this car never had A/C and the hole is round, not oval like the A/C opening would be.  I am curious to know what the purpose of this hole would might have.  There is a slight imprint next to the hole, and a second smaller hole at a slight angle, that may have been from something that was later removed.  The firewall insulation is pierced there also.

Any info is appreciated - Jim

[Bob Gaines]

It looks like the impression left from a hole saw with the drill bit hole in the center.

[CharlesTurner]

Maybe the assembly line worker drilled the wrong hole for the choke cable?  An A/C line hole would have been bigger.

[cobrapatrol]

It looks like the impression left from a hole saw with the drill bit hole in the center.

That's an interesting observation and certainly within the realm of possability. The hole edge is very neat and the (presumed original) firewall paint extends into the hole.  It does not appear to be raw cut like with a hole saw but more like a factory die cut.  There's no impression into the insulation pad at the circumference of the hole like a hole saw would make.  The car was certainly hot-rodded in its past and it might have been cut for an oil pressure line or some such added gauge.

I saw one map of early Mustang firewall in a https://www.vintage-mustang.com/threads/firewall-holes.949033/#lg=thread-949033&slide=0 VMF forum post that was apparently lifted from a Mustang Monthly article.
I cannot vouch for the information but it indicated an oil pressure line hole.  Possibly a Shelby prototype thing?

But the important information from the perspective of Concours Mustang is whether the hole was factory-made.  If the conclusion is no, it is not factory-made, then I will continue to investigate other sites of Mustang lore.

I greatly value your expertise! - Jim