69 frame mounting

[kelly theaker]

has anyone used the newer style rubber body mounts on a 69 with any success or problems. the aluminum spacers are solid, would using the rubber from the 73 and up aleviate any vibration, lessen stress cracks? .is this a worthy option ,. GM obviously made the change for the improvement for the occupants
I understand the need for resto correctness but if this is a great improvement , i would like to use it possibly. thoughts?

[Jim T.]

Re: 69 frame mounting

I converted my original owner 70 over to the 73-82 rubber mounts about 12 years ago after I disassembled it so I could stip the body of paint and repaint it. It was very easy with bumpers already removed, all my mounting bolts came out easy and from what I remember, the only other additional part that I disconnected to lift the body to install the rubber mounts was where the bottom of the radiator support attaches to the removable front crossmember. I only lifted the body enough to replace the mounts. Back in 73 Hot Rod magazine did an article on changing from solid mounts to the 73 rubber mounts for the 68-72 Corvettes and I knew I would do this someday.
The rubber mounts will raise a 68-72 body from the frame. The figure is if I remember correctly about 1/8-1/4 inch. I had no trouble reinstalling my bumpers on my 70. One thing I did do with the front crossmember mentioned earlier is install a spacer washer/shim between the radiator support the removable front crossmember. I did not want to put stress on the front fiberglass by pulling these two pieces together.
Do I think my car is improved? Yes. I would have to agree with the engineers at GM in their decision to change from solid metal to rubber body mounts.

[Terry M.]

Re: 69 frame mounting *TL*

Jim has all the details correct- although I think it raises the body a little more than his dimensions indicate. This was a fairly common improvement in the mid-70s. Do keep in mind, if your 1969 has side exhaust, the mufflers will be exposed more than might be acceptable. Kind of like one's underwear showing.

[kelly theaker]

Re: 69 frame mounting

appreciate your comments, exactly what are the dimensions of the additional lift.The vehicle does not have side exhaust, but does the rocker moulding cover the exposed frame ?

[Jim T.]

Re: 69 frame mounting

This is not really a good reference Kelly, but if you go to the 70 Corvette Registary web page you can see my 70. My car is in the last section. I do not think that it can be viewed in person and noticed. The rocker panels are not high enough to expose the frame. I should of had Terry look at it when I saw him in Bowling Green awhile back and see what his evaluation would be. I did measure the difference from before and after the change, just don't remember the exact measurements.

[Terry M.]

Re: 69 frame mounting *TL*

Kelly,
I doubt the difference would be very noticeable without the side exhaust. If one had a line of early C3s (as on the judging field, or in a display that is organized by year), from a distance one might notice the height difference - just as replacement springs are detectable. One has to be looking for height differences to notice these kinds of deviations, however. Most folks are not looking at that feature, and as the car stands alone the height difference of the rubber bushings will not attract much attention.

[kelly theaker]

Re: 69 frame mounting

appreciate the help, a question on the #4 mount the hole was larger to take the aluminum mount , what i mean is the other alum, mounts are flat on both sides , but the 4th has a larger hole in the frame mount resting area. do they also accomodate the rubber bushes the same .

[Terry M.]

Re: 69 frame mounting *TL*

I don't know the answer to that Kelly, (I have no personal experience with this mod) but IIRC all the instructions I read 25 years ago never talked about having to modify either the body or the frame. It was presented as lift it up and bolt it in modification. Some minor adjustment of brake lines, oil pressure line and transmission to steering column interlock might be needed, but nothing that couldn't be easily accommodated. I can't recall if new longer body mount bolts were necessary, but you will discover that easily in the course of the change.
I do recall that they talked about doing only one side at a time. Loosen all the mounting bolts, but lift only one side and R & R the mounts - then do the other side the same way, and lastly tighten all the bolts.
Maybe someone who has done it will jump in here.

[Jim T.]

Re: 69 frame mounting

I'll jump in again. Terry you are 100% correct about the longer body mounting bolts, my original 70 body mounting bolts were to short for the rubber mounts. The only adjustments I remember at the moment other than what I have alread posted was loosening the steering wheel assembly under the dash and at the firewall since I was going to be lifting the body close to this for the #1 and #2 body mounts. I had no apparent problems with the mounts fitting in the #4 body mount hole.

[Terry M.]

Re: 69 frame mounting *TL*

Yep - I forgot all about the steering column. NCRS disease. Nothing like having actually done the job rather than my book knowledge.

[kelly theaker]

Re: 69 frame mounting

an excellent turnout on the frame mount issue, lets see who else this question draws comment from , and thanks to all members from the Corvette Brotherhood.

[Jim T.]

Re: 69 frame mounting

Kelly I checked your profile and see that you have a convertible. Just want to mention that the coupes and convertibles use different sets of rubber mounts. I have a set of convertible mounts that I bought for my 68 convertible that I plan on changing someday. The difference only affects a couple mount locations on the convertible.

[Harmon C.]

Re: 69 frame mounting

The point of the mounts being different on convertibles is what I thought but the sets I have bought I can't see the difference. Some had a white line on them but they were the same height. Do you know what is different?

[kelly theaker]

Re: 69 frame mounting

Can you describe the differences? The rubber mounts seem the best way to go as far as an improvement. As well changes were made to a door system example - the door alignment pintle . Why did GM originally use the solid mount, they had previously used rubber on the mid year?.While going over rail crossings does the rubber create a more pronounced door chatter or ? and is this why the improvement in the alignment pintle system.

[kelly theaker]

Re: 69 frame mounting

been away wanted to ask what body mounts were different, i suspect you are stating that they put some solid mounts as well as some rubber mounts, is that correct? thanks