For my 1968 Olds Cutlass S I'm wondering which are the correct gaskets for putting back my heater core since the Service Manual doesn't specify except for saying to put a bead of sealer on the heater box.

Fusick shows the below 5 piece set

http://www.fusickautomotiveproducts....?number=HBG642

OPGI shows the below kit:

https://www.opgi.com/cutlass/CH17264/

And Inline tube shows the items which are sold separately (see photos).

Also, I've read that some people have used a seam sealer on the heater box when putting it back on the firewall, and some have used 3M Strip Calk. Inline Tube sells a white rope caulk but that doesn't seem correct since everything is black and I've never seen a photo of a car with a white sealant around the heater box.

Can anyone shed some light on what is factory correct?

 

I have no idea what the product is called - but both my 71 and 72 had the thick putty-like filler that's also used behind the kick panels to make them waterproof.

Having googled Strip Caulk, it sounds similar in application to the factory solution.

 

Yes, I have a box of the 3M Strip Calk which I will use to seal the heater box to the firewall and on the interior box. Just wondering whether the Fusick, or the ILT was the correct foam gaskets.

 

Those are "urban myth" parts (ie - never used on the original cars but now made in an attempt to get more $ from you).

The only "seal", "gasket", etc was a thick/dense foam block that slipped over the two heater core outlets before the INTERIOR box is pushed up against the firewall pad.....this foam block was used to keep hot engine compartment air, etc from coming in through the two heater core pipe holes in the firewall and maybe prevent rubbing/chafing on the two pipes.

Ames Performance Engineering (Pontiac repro parts vendor) makes a very nice duplicate of this foam block (Part # P120M - $12 in their GTO/Lemans/Tempest catalog).

Use the 3M strip chaulk b/n the metal blower motor case and the firewall (engine compartment side). The firewall pad itself serves as a gasket/seal on the interior side of the firewall.

 

I used some of the new 3M strip caulk on the back of some moldings where the pins went through the sheet metal, and is attached with stamped nuts. On one, I needed to remove it a few weeks later, and it was just about impossible to get it loose. The caulk was more like a rubber glue that held the molding to the car without even needing the retaining nuts. I have since done some additional "testing" with the 3M caulk, and have determined that at some time in the recent production, they have changed the formula, and it doesn't work like what was available in early 2000. It is a great sealant, but only use it where you are unlikely to ever take it apart again, unless you want to spend hours trying to cut it apart.

 

Thanks for your input Junkman. My 3M Strip Calk is about 7 years old and must be the old formula since where I have used it previously it is still pliable. And like most who have bought this product, I still have about 58' of the 60' that I bought.

 

Was there sealant or possibly a gasket between the blower motor itself and the box that attaches to firewall?

 

I haven't seen one on my two cars.

 

I have never seen a gasket or sealant on the blower motor.