67 heater box sealant

[James B.]

I am restoring my '67 coupe, now have the body off the chassis and am stripping everything out of the engine bay. A black sealant was used around the heater box, grommets and other areas on the firewall (and liberally dripped down the firewall!). What modern sealant would y'all recommend that matches the original and is acceptable in judging? Once I have that then I will have to practice to be as sloppy as the guy who originally did the job. Thanks, Jim B
edit: After I post something then I think about the archives, so apologies. However the posts on this subject appear to be about 8-9 years old. The most specific was from Joe Lucia, "For C2 era cars, the AIM says that the sealer used for the blower box to firewall interface was neoprene solvent adhesive. This is the same type of cement used for gaskets, weatherstripping, etc. It's what we know today as 3M Weatherstrip Cement aka GM #12345097." Is this still the best answer?

[Ara G.]

Re: 67 heater box sealant

James, there are 2 schools of thought on this issue I think. One believes that the sealant was really used only on the "leakers". I have seen Bowtie cars with the sealant, and without (or very minimal). Tough call to make. Joe's response is a good one in that older post. Other schools of thought believe that all the cars got the sealant to keep water from coming into the passenger compartment from the engine bay. I have seen guys use gritty asphalt/tar, black weatherstrip glue, etc....The consistency, IMO, is close but not exactly like the original stuff....I am sure others will chime in....ARA

[James B.]

Re: 67 heater box sealant

Ara, thanks for the response. I've done some more reading. Comment by John Hinckley and other that it was only applied to leakers is interesting. Guess I have a leaker. I'll go look for submarine sealer....

[Daniel Y.]

Re: 67 heater box sealant

James - I've used plastic roof cement (caulk) to fill the huge cracks and then fibered roof cement on top of that or in tighter cracks. it runs down just like the original did

[James W.]

Re: 67 heater box sealant

Hello James,

There was an article on the Spring 2011 Corvette Restorer Magazine that has info on how to make your own sealant and how to apply it. The author was Duane Ravenburg. I have it in a PDF file if you would like it. I am getting ready to do this same treatment on two of my cars before the national convention.


Regards,

James West

[Chris E.]

Re: 67 heater box sealant

I don't believe my car had the sealant originally. Family owned car since 1973. I did a complete body off restoration on the car, and there was no remnant of sealant anywhere near the heater box on the firewall, nor on the blower assembly. I left it clean and I sometimes lose 1 point in Flight Judging at the Regional / National level. The '67 TIM/JG says "some cars" may have had it. No big deal.

[James B.]

Re: 67 heater box sealant

Thanks Chris, I read about your debate in the archives (2010?). You may remember you judged my car (white/saddle '67 L79 Coupe) at Delafied in Sept. It should be ready for you to judge again late 2015! Trying to retain as much originality as possible. Jim B

[Gene M.]

Re: 67 heater box sealant

Guys, I think you will find that the slop and drip sealant job was only applied to cars that leaked the water test. If John Hinckley will chime in he should be able to completely explain the topic best.

[Edward J.]

Re: 67 heater box sealant

I have had 3 heater boxes apart on mid years lately (non-a/c) and re-call no sealant on any. But would say use a little 3M strip chaulk behind the sealing gaskets and studs should be done regardless.

[Chris E.]

Re: 67 heater box sealant

Thanks Chris, I read about your debate in the archives (2010?). You may remember you judged my car (white/saddle '67 L79 Coupe) at Delafied in Sept. It should be ready for you to judge again late 2015! Trying to retain as much originality as possible. Jim B

Jim, I do remember you and your car! Glad to see you are continuing to campaign the car. Let me know how else I can help, as you and I have the same model year and motor. I should be at the 2015 Delafield Regional. Hope to see you there!
Chris

[Gene M.]

Re: 67 heater box sealant

Here is John Hinckley reply on the topic from previous post.

John Hinckley (29964)
Beyond Control Poster
Join Date
December 1st, 1997
Posts
15,840
Re: Heater box sealant
The gooey, runny black stuff was a water-test repair sealant that was used in repair and intermittently on the main line; it wasn't part of the normal heater blower case installation.