#4 body mount reinforcement question
Thread Starter
Instructor
Joined: Jan 2007
Posts: 196
Likes: 0
From: Ponoka Alberta
#4 body mount reinforcement question
Hey everyone.
I will be replacing my #4 body mounts soon. My question is the reinforcements on the body itself, is there an adhesive that goes in there? I have looked in the AIM but that doesnt tell me much.
I remember in a previous post someone said use polyurethane adhesive I think.
Just need clarification on this.
Thanks for any advice.
Peace.
I will be replacing my #4 body mounts soon. My question is the reinforcements on the body itself, is there an adhesive that goes in there? I have looked in the AIM but that doesnt tell me much.
I remember in a previous post someone said use polyurethane adhesive I think.
Just need clarification on this.
Thanks for any advice.
Peace.
Melting Slicks
Joined: Apr 2004
Posts: 2,008
Likes: 38
From: Space Coast Gator Territory
GM did not put any adhesive between the fiberglass and reinforcement. You can avoid future rust issues caused by debris collecting in any voids by applying silicone sealer before placing the reinforcement. I used s/s pan head cap screws with lock nuts when installing mine. Many different fasteners and sealers have been used for this installation. Choose what works for you and send it home. Wipe excess sealer that is pushed out on installation off with a finger and your done.
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
GM did not put any adhesive between the fiberglass and reinforcement. You can avoid future rust issues caused by debris collecting in any voids by applying silicone sealer before placing the reinforcement. I used s/s pan head cap screws with lock nuts when installing mine. Many different fasteners and sealers have been used for this installation. Choose what works for you and send it home. Wipe excess sealer that is pushed out on installation off with a finger and your done.
Melting Slicks
Joined: Apr 2004
Posts: 2,008
Likes: 38
From: Space Coast Gator Territory
Yes, but only an inch or two. You have to loosen other mount bolts, so the body can be raised enough to slip the support in place. This can open a can of worms if the #2-3 mount nuts turn in the cage on the frame. There are ways to deal with this if it happens, it only makes the job more challenging.
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
Yes, but only an inch or two. You have to loosen other mount bolts, so the body can be raised enough to slip the support in place. This can open a can of worms if the #2-3 mount nuts turn in the cage on the frame. There are ways to deal with this if it happens, it only makes the job more challenging.
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
For an early model (metal mounts), you will likely need to loosen other mounts as suggested above.
I would then lift the body with a piece of plywood under the battery compartment.
Go slow and you don't need to lift much.
For later rubber mounts, there is a little more space in there.
It is possible to lift on the rear body and flex enough to get the reinforcement out.
I don't recommend this unless the other mounts are a can of worms.
I used the polyurethane adhesive to seal and adhere the reinforcement.
I would not use silicone. It tends to peel eventually ... urethane for longevity.
Don't like the idea of getting the adhesive at Home Depot ? ....
use a urethane windshield adhesive, available at most GOOD auto stores (3M window weld).
I would then lift the body with a piece of plywood under the battery compartment.
Go slow and you don't need to lift much.
For later rubber mounts, there is a little more space in there.
It is possible to lift on the rear body and flex enough to get the reinforcement out.
I don't recommend this unless the other mounts are a can of worms.
I used the polyurethane adhesive to seal and adhere the reinforcement.
I would not use silicone. It tends to peel eventually ... urethane for longevity.
Don't like the idea of getting the adhesive at Home Depot ? ....
use a urethane windshield adhesive, available at most GOOD auto stores (3M window weld).
Melting Slicks
Joined: Apr 2004
Posts: 2,008
Likes: 38
From: Space Coast Gator Territory
I lifted the entire body off my 69 by only using the bonding strip edge just inside the rocker channel. When I replaced the body support and mount on my 79, I placed a length of 2X4 along that bonding strip and lifted with a floor jack. Of course, I needed some wood block spacers, but it was a solid lift. Just be careful before you start jacking that nothing is in the way and check a few times while jacking. A moment of indiscretion can lead to years of regret. BTW...I did not disconnect steering, bumpers, or anything else, just loosened the other bolts. I had to loosed them as I was replacing other body mounts. As stated, you may be able to lift without releasing the other mounts, but I never tried it.
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
Well, that reminds me ... chrome rear bumpers IMO should definitely be
loose or removed. The bumpers bolt the fiberglass directly to the frame.
A plastic rear bumper may have similar connections to loosen.
My 75 cam ewith a fiberglass rear bumper mcover, so there was no
connection from bumper to frame, since the supports need to be removed
to install the glass cover.
loose or removed. The bumpers bolt the fiberglass directly to the frame.
A plastic rear bumper may have similar connections to loosen.
My 75 cam ewith a fiberglass rear bumper mcover, so there was no
connection from bumper to frame, since the supports need to be removed
to install the glass cover.
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Melting Slicks
Joined: Apr 2004
Posts: 2,008
Likes: 38
From: Space Coast Gator Territory
I agree about the steel bumpers. Honestly, I didn't think I could do it with my rubber bumper car. Another forum member said he replaced his 79 body mounts without disconnecting anything, so I gave it a try. It worked for me also, but you need to watch everything closely as you proceed. I have nice paint and couldn't afford to cause damage in the process. As long as you work slowly and think everything through it will go OK. Check brake lines, fuel lines, rag joint and body around bumpers as you raise the body. This is getting ahead of the game, first grind off the rivets and see if the old support will come out. If it does, then the new one ought to go in, right?
There is one or two rivets in the back that you can't see without drilling a hole in the splash apron. The rivets are usually corroded enough that they will break with a little prying. If not, a rasp file or chizel will make fast work of the rivet heads and the support should be free. I leave that rivet out on installation.
There is one or two rivets in the back that you can't see without drilling a hole in the splash apron. The rivets are usually corroded enough that they will break with a little prying. If not, a rasp file or chizel will make fast work of the rivet heads and the support should be free. I leave that rivet out on installation.
Last edited by Red 69; Aug 16, 2007 at 04:30 PM.
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
I loosened the bolts on my 77, but I was replacing all of the body mount bushings, too...something I would recommend doing while you're going to the trouble. If the mounts are rotted, it's likely that the bolts are frozen to the capture nuts. New nuts are available from the parts vendors. My car did seem to have some sort of dried-out adhesive remains on the fiberglas under the reinforcement. On the recommendation of several forum members who had previously done the job, I gooped a lot of PL polyurethane construction adhesive into the reinforcement before installation, in order to more fully reinforce the mount and make up for the fact that I could only get screws into two of the four flanges to replace the rivets.
