1960 Heater Assembly sealant - Judging Question

[Donald H.]

I'm hoping to have a 58-60 Judge chime in on this!!!!

Another member started a thread regarding sealant around the heater box (link to his thread below). Not want to interfer with his thread i'm also looking for info so I started this thread. I have looked in the TIM & JG, the AIM, and also the 58-60 Corvette Restoration Handbook and have not found any info.

In Joe's thread he mentions that at a Regional meet the judge told him that the dum-dum was missing and that the foam gasket was incorrect (I think I got that right).

I want to make sure mine is correct for judging, so here are my questions:

For the inner heater box that contains the core and mounts to the firewall - is black dum-dum (3M strip caulk) correct/acceptable to the judges?

For the fresh air inlet housing that mounts to the inner heater box - is black dum-dum also correct/acceptable for judging?

Or, is the thinner black tar like sealant that was used around grommets and other things that went through the firewall what I sould use?


https://www.forums.ncrs.org/showthre...de-of-firewall

Thanks,

Don

[Thomas H.]

Re: 1960 Heater Assembly sealant - Judging Question

Here are a few pics from when I replaced the heater core in my 60.

IMGP6970.jpgIMGP6973.jpg

[Joe M.]

Re: 1960 Heater Assembly sealant - Judging Question

Donald, I believe the asphalt-based sealant is correct, but I purchased a tube last night, ran out a test bead on a board and and 24 hours later, where it is thicker than 1/16", it has a skin, but underneath the skin, it is semi-liquid goo. If you accidentally pop the skin, the goo will make a big mess. Where the bead is 1/16" or less, it is semi-hard and no goo underneath the skin. I suppose you could build up several thin layers over a several day period and you wouldn't have a messy goo problem. One problem that I foresaw was placing a thin bead with a caulk gun in the narrow crevasses. Even when I pulled back on the caulk gun handle, which usually stops the flow, it continued to ooze out fast enough that it dripped before I could grab a paper towel and wipe it off. It is soft enough that I believe you could pump it into a bakers icing bag with narrow nozzle and hand squeeze it into the crevasses.

I purchased a box of 3M black strip caulk today and it will work just fine and not create any type of asphalt goo problem.

[Donald H.]

Re: 1960 Heater Assembly sealant - Judging Question

Donald, I believe the asphalt-based sealant is correct, but I purchased a tube last night, ran out a test bead on a board and and 24 hours later, where it is thicker than 1/16", it has a skin, but underneath the skin, it is semi-liquid goo. If you accidentally pop the skin, the goo will make a big mess. Where the bead is 1/16" or less, it is semi-hard and no goo underneath the skin. I suppose you could build up several thin layers over a several day period and you wouldn't have a messy goo problem. One problem that I foresaw was placing a thin bead with a caulk gun in the narrow crevasses. Even when I pulled back on the caulk gun handle, which usually stops the flow, it continued to ooze out fast enough that it dripped before I could grab a paper towel and wipe it off. It is soft enough that I believe you could pump it into a bakers icing bag with narrow nozzle and hand squeeze it into the crevasses.I purchased a box of 3M black strip caulk today and it will work just fine and not create any type of asphalt goo problem.

Joe,Are you putting the dum dum on the surface of the fiberglass heater core box and again on the metal shim that goes between the heater core box and the firewall?

What about between the outer fresh air valve cover and the heater core box?I see three surfaces that could or should have sealant (see the attached picture). I still trying to understand if sealant should go on all three surfaces. I remember cleaning the goop like Thomas pictured above off the inside of the firewall. A

lso, are you sure the 3M strip caulk will pass judging. It's a pain to take the heater assembly apart as I'm sure you will agree. So hopefully both of us can get it right this time!!



Heater sealant-2.jpg

[Joe M.]

Re: 1960 Heater Assembly sealant - Judging Question

i am only putting the black dum dum between the fresh air valve cover and the heater core box; #3 on your photo. That is the only area the judges can see. I am not certain of the 3M black strip caulk being accepted, but I will take last years judging sheets for reference if it comes up. Each judge sees the small things a little different Big items are standard. It is the little things that appear to be subject to individual interpretation.

[Ian G.]

Re: 1960 Heater Assembly sealant - Judging Question

it comes down to if a judge has taken one of these cars apart nuts and bolts and has seen how each of the things really was vs reading about it, or working on a later restored car where these details have been lost. Also, whether they want to ding owners on details that aren't documented, but they know to be original... Judges get tougher in regional and national events, but again it comes down to the individual. I';m going to use the asphalt dum-dum, but some judges will care and others won't... You could use regular dum-dum and just dribble a little of the asphalt around the edge to get the best of both worlds...