1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

[Peter M.]

Reference C2 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts ... On page 150 of the 6th edition JG it describes pal nuts as black phosphate for heater box cars. On page 151 it describes the evaporator housing for AC cars but does not seem to address the stud mounting nuts and finish ...did I miss that somewhere else in the JG? Are these nuts black phosphate finish like heater box cars or cad?" Thanks all.

[Rocco S.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

Peter, I don't know if this helps you but here are two photos of the firewall nut in question on my 1967 survivor coupe with A/C. This nut was recently removed to repair a leaking heater core. It was covered with a black sealer. Evidence of the sealer can be seen in the photos. I did not clean the nut. Just re-installed. It looks like it was originally black phosphated not zinc or cad plated. Regards, Rocco
Firewall Nut 1.jpgFirewall Nut 2.jpg

[Peter M.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

thanks - that faster on your 67 is a PAL nut which is different than the full thread nut my 66 came with.

[Mike B.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

Good Evening Peter,

I'm away from my '66 AC car here in Florida so I'll reply to your thread from memory and also with the help from an excellent file photo provided to us by Jeremy Rust. Jeremy recently posted a great array of AC hardware photos from his '66 AC system.

When I took my evaporator box off of my firewall these solid wide flanged nuts were in very good shape. Mostly due to a good covering of grime but some also had a thick coating of blackout. They appeared to have been either brushed or mitted over resembling Rocco's photo. Drips and all. Especially around the 3 nuts that hold the H2O SOV metal cover plate in place. Looking at the underside of these wide nuts I could clearly see that they were either zinc or cadmium plated. Look at Jeremy's photo. Mine are an identical match.

What's noteworthy here is that I had these type nuts in 3 separate areas of my '66 convertible:

(8) Identical to the photo here from my evaporator box and heater core cover plate. Some with "E" logos and some no logos. See photo.
(2) Identical with "E" logos securing each door's lower fin window attach point.
(2) Identical with "RBW" that secure the sides of the rear valance panel. The one's on my valance appeared to be gray phosphate.

Hope this helps. Mike

Jeremy 6 (2).jpg

[Jeremy R.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

Yeah I asked the same question recently and the limited response I got back it seems that it could be either the collared nuts (whether zinc or phosphate or mix of both), PAL speednuts or a mix of both that held the housing on the firewall. It seems that more of the PAL nuts might have held on the heater core cover, thought my picture above of the one collared nut with the thick black coating was at the foremost to the center firewall nut on the heater core on my 66. Not sure if this was any different from year to year.

I hope more A/C people chime in

[Mike B.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

Well, after viewing my '66 AIM I've realized that there were 9 (not 8) of these solid wide flanged nuts on my '66's AC system. These nuts are part number#446069. Yes, there were 8 of these on the engine side of my firewall but there's also one on the far right hand side of the inner firewall. This lone inner "flanged" nut is tough to see when installed.

It's stud is part of the evaporator/blower assembly that then passes through it's seal, then through the inner lower corner of the adapter assembly, then through it's seal, the firewall, then through the inner distribution box seal then finally through the rounded tab on the far right side of the distribution box. There appears to be an error on AIM C60 sheet A2 that states that this stud is part of the adapter assembly bracket? See the attached evaporator box photo here and also AIM sheet D5. The stud is part of the evaporator box.

If anyone reading this is about to remove their inner distribution box be very careful not to miss the large black "PAL" nut supporting the inner end of this box. The AIM simply states "Production Nut" there. It might be buried under insulation. Be careful.

So, if anyone has their far right inner "flanged" nut loose and could post a shot here it would be very helpful. Mike

Evaporator Blower Assy Inner (with arrow).jpgOuter Side (1).jpgInner Side (1).jpg

[David B.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

# 446069 1/4 - 20 phosphate coated GM 4435 - M Code A Stamped Steel, formed Thread, plain flange type
GM 4435 - M requires treatment with oil base compound to provide 72 hour salt spray test

[Peter M.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

David - thank you for your reply .. can you please advise the source of this information ... also my original car has both M code and RBW markings. Does your information represent all C2 production variants from 1963 - 1967 or a specific year?
thank you.

Peter

[David B.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

Source is GM specifications for PN 446069. It does not specify where to use. The Fastener Engineer makes the call on variations and the AIM lists what part # to use. Provide a variation part # and I might be able to give it's specification. I remain neutral!!!

[Garry M.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

My mid-Nov production '66 has a combination of PAL nuts and Flange Nuts. All are black phosphate.

AC PAL Nut.jpgAC Flange Nut.jpg

[James W.]

Re: 1966 Factory AC Evaporator housing - firewall mounted evaporator box stud nuts

I know you are requesting information about 1966 a/c evaporator box nuts, but my un-restored '65 has a combination of both flanged and pal nuts. It has only been apart to replace the heater core in 2009.

Regards,

James