Press mould or SMC?

A

aussiejohn

Member
Joined
Aug 19, 2009
Messages
16
Location
Highett, Australia
G'day,
I have received an enquiry from an Aussie Corvette owner who wants to know if his 1974 body was made in Press Mould or SMC. I seem to recall that SMC was first used on the C4s, but you guys will have the answer.

Can you help?

Thanks and,

Regards from Down Under:drink:

aussiejohn
 
aussiejohn said:
G'day,
I have received an enquiry from an Aussie Corvette owner who wants to know if his 1974 body was made in Press Mould or SMC. I seem to recall that SMC was first used on the C4s, but you guys will have the answer.

Can you help?

Thanks and,

Regards from Down Under:drink:

aussiejohn
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G'day! SMC it is. The back of the panel will be smooth. It almost looks like plastic and the color has a light grayish tint to it.

Danny
 
smc was first used in 82 wasn't it? Thats the year GM experimented with lighter weight through thinner glass and the smc.
 
vette said:
JeffP1167 said:
smc was first used in 82 wasn't it? Thats the year GM experimented with lighter weight through thinner glass and the smc.
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no. They started much early then that.
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Yes, apparently, my '72 rear deck is that slick gray looking material, and gave me troubles on filling in the vent grills, even using SMC supposed compatible materials....I even redid it, still a mess....only fair at best....

the front is brown, and looks like that random glass matting...

:beer:
 
When I went to Carlisle this year I ask that question to the GM group. To my surprise they didn't know but, said ask a retire guy named John at the gm tent. Here is what he said." In the early 70's they started using SMC (not the kind that is used today) on flat panels at first." "So, the early cars contained both because the tooling was very expense to make." "As the years went on so did new tooling replace old until the whole car was SMC?" He even told me how it was made but, that would take a good 1/2 day to explain so I won't go into it. Your car is all SMC.

Danny
 
vette said:
When I went to Carlisle this year I ask that question to the GM group. To my surprise they didn't know but, said ask a retire guy named John at the gm tent. Here is what he said." In the early 70's they started using SMC (not the kind that is used today) on flat panels at first." "So, the early cars contained both because the tooling was very expense to make." "As the years went on so did new tooling replace old until the whole car was SMC?" He even told me how it was made but, that would take a good 1/2 day to explain so I won't go into it. Your car is all SMC.

Danny
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That is correct. In the early '70's we see bodies with both PM and SMC. but not very often. Pretty much all SMC by the mid to late 70's.
 
big_G said:
vette said:
When I went to Carlisle this year I ask that question to the GM group. To my surprise they didn't know but, said ask a retire guy named John at the gm tent. Here is what he said." In the early 70's they started using SMC (not the kind that is used today) on flat panels at first." "So, the early cars contained both because the tooling was very expense to make." "As the years went on so did new tooling replace old until the whole car was SMC?" He even told me how it was made but, that would take a good 1/2 day to explain so I won't go into it. Your car is all SMC.

Danny
Click to expand...

That is correct. In the early '70's we see bodies with both PM and SMC. but not very often. Pretty much all SMC by the mid to late 70's.
Click to expand...

Even though the number on engine/tranny still 'matched' when I got this car, the thing was heavily modded as a show car doing the mid atlantic circuit....I dunno exactly who did what/where....but I am told the second of the two chicks who owned it, reduced the flares down to existing shape and painted it burgundy....

see sites for a couple old pix.....

so someone either switched panels, or what, who knows?? but the old body work was done by someone in the know, as it's never cracked or messed up, just wish I was 1/2 that good at it....

:)
 
Thanks for your answers

vette and Big_G and others,
Thanks you all for your rapid response. I have replied to the enquirer and suggested that he look here for a more detailed answer. He might even like to join us here.

It is interesting that there was little if any information emanating from GM about the change to SMC in the seventies. It seems that today, there is virtually nothing that isn't known about every C3 ever built, such is our passion for the car, yet I did not find any reference to this in Mike Antonick's Black Book. Perhaps if anyone here knows him, they might suggest that he research this for possible inclusion in a future edition of the Black Book.

Regards from Down Under:drink:

aussiejohn
 
it was in C3 era, I want to guess 73.
I think (CRS) recall that 73 only right side inner fender skirt was SMC when sold in service at GM franchised stores i.e. dealership. Earlier model inner fender skirts over the counter were press molded fiberglass.

In some ways I feel so lucky. Thirty five years ago I decided to put a new door to door front end on my split window because it had been tapped here, there and everywhere. At that time I could still buy all brand new GM press molded fiberglass panels and all the bonding strips instead of hand laid aftermarket. Some of these were not the creamy white of 1963 original glass, but WTF it all gets painted and blacked out inside. There is nothing like an original part for fit and finish, although some come close today.

In later years when GM service still sold the top surround panel, it was in SMC not press molded fiberglass as original. I still have one GM SMC 63-67 surround, as a back up in case I get hit.
 
Geoff Coenen said:
it was in C3 era, I want to guess 73.
I think (CRS) recall that 73 only right side inner fender skirt was SMC when sold in service at GM franchised stores i.e. dealership. Earlier model inner fender skirts over the counter were press molded fiberglass.

In some ways I feel so lucky. Thirty five years ago I decided to put a new door to door front end on my split window because it had been tapped here, there and everywhere. At that time I could still buy all brand new GM press molded fiberglass panels and all the bonding strips instead of hand laid aftermarket. Some of these were not the creamy white of 1963 original glass, but WTF it all gets painted and blacked out inside. There is nothing like an original part for fit and finish, although some come close today.

In later years when GM service still sold the top surround panel, it was in SMC not press molded fiberglass as original. I still have one GM SMC 63-67 surround, as a back up in case I get hit.
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Real glass is better for spider veins, that's about it.
 
JeffP1167 said:
smc was first used in 82 wasn't it? Thats the year GM experimented with lighter weight through thinner glass and the smc.
Click to expand...

There's a lot of confusion regarding that, mainly because people use the name SMC for the stuff on C4 corvettes. It's SMC but not the same as the C3 panels. The 82 was the first to use the C4 type stuff on the hood and doors. They really ARE different from the earlier stuff. It's a lot more resin and much less fibers.
 
"Real glass is better for spider veins, that's about it."

Didn't they stop making real Vettes in 69? Fuelies, Tripowers, dual quads, KO's, side pipes, L88s, L89s, all gone :D newer Vettes are at best a 2 seater Caddilac with brittle marbelized SMC. No character, No sink marks, no rivet heads like in aged fiber glass. :D Too smooth, sterile :D
 
Geoff Coenen said:
"Real glass is better for spider veins, that's about it."

Didn't they stop making real Vettes in 69? Fuelies, Tripowers, dual quads, KO's, side pipes, L88s, L89s, all gone :D newer Vettes are at best a 2 seater Caddilac with brittle marbelized SMC. No character, No sink marks, no rivet heads like in aged fiber glass. :D Too smooth, sterile :D
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and TOO QUIET!!!!!:trumpet::harhar::devil:
 
Smc?

mrvette said:
Geoff Coenen said:
"Real glass is better for spider veins, that's about it."

Didn't they stop making real Vettes in 69? Fuelies, Tripowers, dual quads, KO's, side pipes, L88s, L89s, all gone :D newer Vettes are at best a 2 seater Caddilac with brittle marbelized SMC. No character, No sink marks, no rivet heads like in aged fiber glass. :D Too smooth, sterile :D
Click to expand...

and TOO QUIET!!!!!:trumpet::harhar::devil:
Click to expand...

I have a 73 and it all appears to be SMC, I have done a lot of body work on it using SMC resin, back side is smooth in all locations that I have worked or can see.
 
1966: First sheet-molded composite (SMC) used for front body panels and hood.

1970: Plenum and instrument panel support panels switch to SMC.

1971: Rear quarter and end panels switch to SMC.

1984: One-piece, lift-off SMC roof panels introduced.

1993: Rear inner panels molded from recycled SMC, an industry first.


The C4's used what is known as "short strand" smc and that largely accounts for the difference in appearance.


The chemistry of smc improved yearly and only smc producers and gm know for sure the actual composition.
 
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