#4 Body Bolt Nut Attachmnet

[Duane D.]

My 1970 Corvette convertible was discovered by an NCRS judge to have a missing #4 body bolt on the RH side. I purchased a new bolt, washer and spacer from Richard Fortier and tried to install without success. Pulling the carpet back, I found a loose, out of place, severely rusted nut. I know I need to buy a new nut assembly, but how is it attached and positioned to keep from spinning? Once installation is complete, is the bolt assembly painted black? Thank you for responding.

[Steve L.]

Re: #4 Body Bolt Nut Attachmnet

Since no one is responding.

The nut cage is riveted to the body by aluminum rivets. The head of which is trapped between the #4 body mount sheet metal located on the outside.

The only way of doing this properly is removing the #4 body mount, place the rivet in from the outside and upset the rivet from the inside.

I did this late last summer, but I have the body off the frame and had to replace the body mount anyways.

Upsetting the rivet from the inside was no easy task. There is no room( on a coupe) to swing the hammer. I used a small air hammer, made my own very short bit. You have to do it by feel since you can't get in there because of limited access.

The head of the rivet has to be under flush with the outside of the fiberglass. There is a recess in the fiberglass for the head.

Doing it this way is correct but a real pain. Someone may have other suggestions.

[Chuck S.]

Re: #4 Body Bolt Nut Attachmnet

A good illustration is shown in the 70 AIM, UPC1, Sheet B4. See Views A and B for relationship of body, nut cage, and reinforcements.

This repair can not be made with the body on the chassis because the outside reinforcement covers the heads of the nut cage rivets.

[Wayne P.]

Re: #4 Body Bolt Nut Attachmnet

Just my two cents worth. Have you tried a good penetrating oil .
Then work the bolt in and out till the rust loosens. My bolt was rusted so badly that the nut and cage spun . Ended up drilling it out. Good Luck. Could be worse.

[Steve L.]

Re: #4 Body Bolt Nut Attachmnet

In my opinion, this is just one of many cases of poor design with many of the riveting locations.

The bolt goes right through the fiberglass body to the inside. These nuts and cages rust out because water gets in through the bolt opening. Not from water getting to this location from inside the cabinet.

The easiest solution is to get a nut, hold it down while tightening the body bolt, then glue the nut cage in place with epoxy. You could even add fake rivet heads to the nut cage. Once the bolt is tightend, the nut cage is useless unless you want to undo the bolt in the future. But then reverse the above proceedure.l

[Duane D.]

Re: #4 Body Bolt Nut Attachmnet

Thanks everyone for responding. I am going to try the epoxy solution. The original rivets may still be in place. At this point, I can't tell since there is so much dirt in the area. My new concern is slightly jacking up the body to slip the 1/2" aluminum pad into place. Do I paint the new body bolt and pad?

[Timothy B.]

Re: #4 Body Bolt Nut Attachmnet

Duane,

I don't know if this will help but I will suggest it for you to think about.

If you can loosen the other side rear mount, remove both rear tires and put some blocks under the main frame box behind both doors. When you let the frame down on the blocks the rear frame section will lower itself because there is no support. This may allow enough room for you to complete removal of the #4 mount assembly.

I have never done this before but I have witnessed the frame flex at the rear. This is one reason the body is best shimmed with tires on ground and weight on the frame.

[Steve L.]

Re: #4 Body Bolt Nut Attachmnet

Thanks everyone for responding. I am going to try the epoxy solution. The original rivets may still be in place. At this point, I can't tell since there is so much dirt in the area. My new concern is slightly jacking up the body to slip the 1/2" aluminum pad into place. Do I paint the new body bolt and pad?

That's a good point. Your rivets are most likely still there. My cage was completely gone but the rivets survived. I dremelled them out from the outside but my body was off and I was putting in a new body mount bracket in anyways.

You can probably drill out the rivet holes on the nut cage just enough to clear the existing upset rivets and then epoxy the cage down. I bet that if you did it carefully, no one would even notice this from the original.

Some else need to comment on the bolt and spacer finish. I have rubber and my new bolt came as black phosphate from the vendor which doesn't mean anything. 3/4 of the bolts come as yellow chromate which never existed.

[Chuck S.]

Re: #4 Body Bolt Nut Attachmnet

Thanks everyone for responding. I am going to try the epoxy solution. The original rivets may still be in place. At this point, I can't tell since there is so much dirt in the area. My new concern is slightly jacking up the body to slip the 1/2" aluminum pad into place. Do I paint the new body bolt and pad?

The spacer is natural aluminum; the washer is black phosphate; the bolt is cadmium or zinc.

What about shims? Unless this body mount has zero shims, and only one location is likely to have zero shims, the shims are natural steel with the corners turned down over the aluminum spacer.

[Harmon C.]

Re: #4 Body Bolt Nut Attachmnet

If you can live with the parts in the pocket inside not being correct pull the rusted cage nut out. Get a large flat washer lock washer and nut that fits your bolt at the local hardware. Have a helper hold the nut inside and your repair will never be seen from the outside or the inside after the convertible spring mount is reinstalled.