Replacing both rear quarters and outer wheelwells on a 65 Malibu. Both were hacked up pretty badly, but I've found remnants of "putty" on the drivers' side between the wheelwell and the qtr panel. Not at the wheel opening, up several inches where there are two vertical ridges on the wheelwell. Makes sense that something should be there to prevent potential rattles. Should I just use a couple globs of pliable body putty and let it squeeze where it wants as the panel gets fit?

there welded to each other on my 69

Removing my 70's rear quarters I found the same thing above the wheel well, and also in the sail panel area. I also want to know where to get this stuff and how to apply.

you can use 3m brushable seam sealer. it was the factorys way of trying to seal an area and keep it from accumulating moisture.

you can use 3m brushable seam sealer. it was the factorys way of trying to seal an area and keep it from accumulating moisture.i have been using expandable construction foam. After the qtrs all welded up i put a long extension on the tube and shoot it between the sail and qtr. and above the wheel well where that glob of factory doodoo goes. I took a qtr off a rolls a few years ago and thats what they used,, Good enough for me when it expands it really seals it up.

lourd fuser products are very good and all kinds of stuff for what your looking for. the thing you need will expand but not push the metal out

i have been using expandable construction foam. After the qtrs all welded up i put a long extension on the tube and shoot it between the sail and qtr. and above the wheel well where that glob of factory doodoo goes. I took a qtr off a rolls a few years ago and thats what they used,, Good enough for me when it expands it really seals it up.
The problem wih most expanding foams is...they hold moisture. They are meant to be an insulation, not to seal out moisture. I have fixed cars that have that behind panels, and guess what? they were rusted!!
You can use a spray in type of undercoating also. I have a gun that shoots a product called "Body Shutz" it is a heavy bodied undercoating, like what you would use under your car. That also wrks in that area after the installation of the panel. Use the "brushable seam sealer" during the installation, and the undercoating after the installation. One other minor problem i have seen with the expanding foam....it can warp a panel out of shape when expanding. i know, it has happened to me. duramix makes a foam style product that doesnt expand with as much force and will fill the voids also.

The problem wih most expanding foams is...they hold moisture. They are meant to be an insulation, not to seal out moisture. I have fixed cars that have that behind panels, and guess what? they were rusted!!
You can use a spray in type of undercoating also. I have a gun that shoots a product called "Body Shutz" it is a heavy bodied undercoating, like what you would use under your car. That also wrks in that area after the installation of the panel. Use the "brushable seam sealer" during the installation, and the undercoating after the installation. One other minor problem i have seen with the expanding foam....it can warp a panel out of shape when expanding. i know, it has happened to me. duramix makes a foam style product that doesnt expand with as much force and will fill the voids also.I am gonna try your way on the chevelle I'm doing now,, the foam i did use on the last one was made by DAP and the stuff is waterproof, sandable and paintable.. but i was always worried about the panel distorting when that stuff dried. It said minimal expanding.. What if you put in nothing? do you really need anything back there?

you actually dont. most people dont. i prefer to spray in a heavy coat of undercoating when finished. maybe not the right way...but my way. and it has worked for me for 25+ years..

you actually dont. most people dont. i prefer to spray in a heavy coat of undercoating when finished. maybe not the right way...but my way. and it has worked for me for 25+ years..water should not get in the sail area unless the wheelwells have holes. I am going to try the stuff mentioned above.. i think gm put it there for a reason, maybe to make the car feel more solid or keep a panel from vibrating.. i always use something and was never able to figure out what gm uses..They also did not use a lot of it, just enough to sandwich between the qtr and the inner w well.

if water sgouldnt get in there, then why do they rust out?? lol
it can leak through the rear window area and the quarter glass area.

i noticed on my 65 that in the between the quarter and the inner wheel well is what appears to be rubber stop sandwiched between the two. I will bet pics when I get it cut out.

I am planning to spray Por 15 inside the quarters as far as I can reach.