1971 cuda firewall coolant hole size

[culp71]

hello all, on a 1971 cuda 340 shaker (no AC) what is the size of the holes in firewall for both coolant hoses?
(upper and lower diameter)

[4Cruizn]

Without measuring . . . I would say they look like 1/2 inch pipes.  But let's have someone measure and get a correct number . . . 

[anlauto]

The heater core should have one 1/2 hose and one 5/8 hose. I would guess the two holes in the firwall are both the same around 1''    You're missing your shaker cable hole though...

[culp71]

around 1 it is. (very observant about missing shaker cable hole....not my car, just a goggled pic for reference)

ill cut both holes to 1 inch inside diameter then.
thanks

[AARTA340]

This may help also. THis picture shows that one may be slightly smaller than the other. Another with the shaker hole.

[anlauto]

I have to agree..the holes do look slightly different size.

[culp71]

yes,  it would appear (and previously thought) that top hole is larger then bottom hole.
anyone have precise measurements for these, I don't really just want to guess, or cut huge holes.

[CudamanTom]

I just measured the holes for the coolant tubes (my engine and my heater box is not installed so as to get precise is easily done).
The top hole is 1"
The bottom hole is 7/8"
Precise 

[culp71]

excellent, thank you, top 1 inch
bottom 7/8, done.

[CudamanTom]

And to add, I was looking at the thick tube insulators that go between the box and firewall and you probably could get away with the bottom hole being 1" as well, as long as the tube is centered with the hole. If that matters from buying another drill bit.