Mystery body mount cushion on 63s

[Tracy C.]

Wondering if any of the 63 gurus can help with a question from a thread on another forum. The 63 body mount kit from Corvette Central contains a couple of rubber chunks similar in size and configuration to a well worn caulkboard eraser. The picture below shows the remains of an original installation for these parts on the rear crossmember of a coupe chassis.

Two or three of us with convertibles didn't have these pieces, but a couple of owners of coupes did. I didn't see them in the AIM nor did I find any previous discussion in the archives.

Anyone know what these cushions were for? The only application I can think of would be a floor support for the "jump seat" that never made it into the production coupes.

Do any other 63 owners have these on their frames?

thanks,
tc

[Michael G.]

Re: Mystery body mount cushion on 63s

Tracy,

My December '62 built coupe had the rubber blocks. Best guess blocks were additional support for floor in cargo area.

[Doug F.]

Re: Mystery body mount cushion on 63s

same cushion was used on 62 and earlier, i've owned a couple of early 63's under #700 and they had em, my # 11000 car doesn't, my guess is they used up existing stock and then discontinued them

[Tracy C.]

Re: Mystery body mount cushion on 63s

Doug / Mike,

Thank for the replies, If they were used prior to 63, then they were probably used on the early 63 convertible models as well. I was thinking this was a part used only on coupes.

Sounds like I'm safe leaving them out of my July 24 convertible regardless.

Appreciate the help,
tc

[Jack H.]

Re: Mystery body mount cushion on 63s

Anyone know what these cushions were for? The only application I can think of would be a floor support for the "jump seat" that never made it into the production coupes.

What's that?

[Duke W.]

Re: Mystery body mount cushion on 63s

They are there to prevent the large flat portion of the rear compartment floor pan panel from "drumming". Interestingly, they were missing from my March-built SWC, which explains why my car always had a noticeable exhaust resonance at about 2000 revs. I don't know how I discovered they were "missing". I fabricated my own using several layers of thick rubber mat stock. I might have seen them in the AIM or shop manual or I might have seen them on other C2s

Can we get some more reports on their C2 useage - sequence number or approx. build date? I would be surprised if they were discontinued as they really make a difference in NVH.

"Jump seat" would be a reference either to the aftermarket rear seat that became available or the stretched '63 mockup that had a small rear seat.

Duke

[Timothy B.]

Re: Mystery body mount cushion on 63s

These cushions/shims are also called out in the 63 shop manual just like Tracy's picture. I would use them as they support the rear compartment floor.

My November 1962 built S/W coupe only had one on the drivers side but I installed another. I had to lift the floor just slightly to install the passenger side cushion. I guess if it did not slide in they left the cushon out.

[Duke W.]

Re: Mystery body mount cushion on 63s

Yes, but I don't see them in the AIM. It's possible they were dropped, which was a bad decision. The rear compartment floor exhaust resonance drumming is probably more noticeable on a Coupe than Convert.

Duke

[Tracy C.]

Re: Mystery body mount cushion on 63s

Appreciate the input Duke. I didn't find these in the AIM either. Tim mentions a blip in the service manual although I haven't cracked mine open to see if I can find it.

Might these be a service part only to address the drumming issue you mentioned and not something installed on the production line?

tc

[Timothy B.]

Re: Mystery body mount cushion on 63s

Tracy,

If you look at the picture on page 1-33 in the shop manual these cushions are referred to as shims.

[Duke W.]

Re: Mystery body mount cushion on 63s

They are shown in Fig. 72, page 1-33 of the 1963 Corvette Shop Manual and called out as "shims".

The logical place to show them in the AIM is Sect. 1 Sheet 62. In fact this illustration is clearly the same as the shop manual illustration referenced above, however, the only change in the record is "8", which means the prior 7 were eliminated to make more room in the change record.

When I disconvered they were "missing" I could not find them in service parts.

It's important to remember that the Shop Manual refers to the vehicle configuration early in production. The AIM, as reproduced, represents final production.

In some cases the change record on each AIM sheet shows all the changes from initial release, however, once the change record space was filled, prior change notes were usually deleted except for the last change. Also, some illustations were "redrawn and revised", which eliminates all prior changes from the record.

So it appears that these "shims" were eliminated, which surprises me as they give rise to and upleasant exhaust resonance at about 2000 RPM, which was quite noticeable in my SWC (3.08:1 axle) at about 50 MPH in top gear.

I'd still like to hear from those who have later AIMs and anyone with '66 body service manual to see if there is any mention of them.

In any event, I think they are a good idea for any C2. They can be seen with the spare tire carrier tub removed, and if not there, they are easy to install, and I don't think their presense or absence is detectable in Flight judging.

Duke

[Michael F.]

Re: Mystery body mount cushion on 63s

They are there to prevent the large flat portion of the rear compartment floor pan panel from "drumming". Interestingly, they were missing from my March-built SWC, which explains why my car always had a noticeable exhaust resonance at about 2000 revs. I don't know how I discovered they were "missing". I fabricated my own using several layers of thick rubber mat stock. I might have seen them in the AIM or shop manual or I might have seen them on other C2s

Can we get some more reports on their C2 useage - sequence number or approx. build date? I would be surprised if they were discontinued as they really make a difference in NVH.

"Jump seat" would be a reference either to the aftermarket rear seat that became available or the stretched '63 mockup that had a small rear seat.

Duke

My April 63 convertible has them.