I have completed my frame including entire drivetrain rebuild (engine, trans, rear, suspension, exhaust, etc.) and have set the body back on the frame ready for bolt up. This may have been addressed before but I could not find the thread.
'69 Chevelle Cp (SS396/Auto)
There are 2 additional bolt locations in the body support approx. half way down the rocker panel that have nuts installed. When I took the car apart these only had pads (no bolts) at this location. The replacement body mount kit also only had pads for this location. Considering the torque of a BigBlock, I would think that adding a bolted bushing at this location could only help, or would this cause too much stress on the body. As it is, the body was only bolted to the frame with 8 bolts (four corners of the floor pans & four corners of the trunk) plus the 2 for the core support. Would appreciate some expert advice on this. Thanks, Joe

Joe, I found the exact same thing while taking the body off of my 70 SS 396, 4-speed. I asked the same question and all that responded said this was the way it was done. 10 bushings with 8 of them bolted, on coupes. Assembly manual backs this up.

I'm not sure if it would be a good idea to bolt these locations or not. I have a 69 Malibu convertible and a 69 SS hardtop and am confident you both have the right information for your cars. The convertible uses the bolts in the additional locations and in addition adds a second bushing in the front corners w/o bolt (not sure about the bolt, would have to look).

I've done the body off restoration on the convertible and replaced all bushing and was considering using the same set of bushings on the hardtop to increase stiffness when the time comes. The cost difference is only about $30, does anyone have an opinion about this?

Figures, no definitive answer on this. Illustration in the Ground Up catalog shows that location (#3) as having a Bolted Mount for Convertibles and a pad for Coupes. I also shows a pad only at location #5 (above the spring pad) for PickUps/ElCamino and wagons. Year One illustration shows either pads or bolted mounts in all locations. I am really tempted to use a bolted mount at location #3 (have an extra pair available)and install the leftover pads at location #1 like the convertibles do. My guess is GM had the floor pans made the same for both hardtops and convertibles and decided these could be eliminated on the Coupes. If I find something to the contrary later on, I could probably just remove the bolts. Got off from work early today was hoping to put in some shop time this evening.

Hey Joe,
I plan on dropping :eek: , I mean mounting the body back on my 72 SS big block coupe this weekend. Like you I put the bushings according to the instructions in the kit. I also questioned why those middle positions were not bolted. But after looking on the 72 Chevelle service manual, I guess thats how it was done. I'm not going to second guess the service manual or GM though.

Good Luck!
Mike

Will it really make any differance? The motor and drivetrain are all mounted to the frame, not the body. I suppose the engineers had a reason???? I'm no expert, just something to think about

From the responses I have received to this post, we are all in the same situation. It doesnt make such sense to eliminate the center support bolts on the Coupes like the factory did originally but I have not received a single response where anyone had indicated they had included these at the time of remounting the body to the chassis. Never did make it down to the shop tonight. Will have to sleep on this till the weekend now and make a final decision. I kinda wander if this was a cost cutting issue and if GM may have done differently on a Buick, Pontiac or Olds intermediate. Will have to look into this.

Just a thought--it may be that the convertible body was bolted on to strengthen it. I know that modern convertibles are beefed up in the rocker area to help stiffen the car. If the old cars were also built that way, then bolting to the frame in 2 more places would tend to stiffen the body structure.
The coupes & sedans wouldn't need this extra support because the roof would provide it. It probably doesn't hurt anything to bolt a roofed body to the frame. I also know that on my 68 the body doesn't come out far enough to put the #1 bolt anywhere. The frame has a hole in it, but the body stops 6" from where this hole is. :confused:
BL

Joe. You stated you did not receive one 'positive' reaction on the extra 2 bushings. This is one.

My 66 has the same provision, just in front of the rear wheels. Like said before, these extra bushings were meant for convertibles only. Their frames are boxed and the body is more flexible because the roof is missing.

The kit I bought included the extra 2. like you, I had to make my choice. I decided on mounting the 2 as well. I have been driving for some 8000 miles now and there is no problem at all. Nor can I say it provides some advantage.

Rob

Rusty66/Rob

I tried to look for some B-O-P intermediate restoration sites for a comparable post - no luck yet. I would think that the extra 2 bolts in the middle of the frame section could not hurt anything but may take away that little bit of body on frame shudder that we are accustomed to by reducing the frame flex at that point. My only concern was transferring torsional frame vibrations into the body itself and maybe winding up with a stress problem in the roofline. I'm probably overkilling this now. I have the bushings w/bolts available. I think I will put these in and see how it works out.

Obviously you can do what you want, but the factory left two bolts out for a reason. Why second guess that? I would leave them out.

On my 66 SS hardtop, ALL the bushings were bolted. Judging by the looks of them, I'm pretty sure they were original & not replaced before I aquired the car (it was only 8 years old when I got it). I've never had any problems before or after replacing the bushings with all of them being bolted.

MikeSibbitt
66 396 SS