When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Can anybody shed some light on the materials GM used to create the hood from my 71 and the nose from a 72?
Here are some pictures: Light gray in color...Lighter spots show where the DA just scuffed the surface when stripping...Dark spot is a repair made long before I bought it. Close up shot of the hood. Label on underside of hood. Underside of hood. Support frame and skin are drastically different in color...hood is relatively smooth on both sides. Smoother than the inside of the fenders. Close up of hood and headlight support bar area. Close up of the outer surface of the nose. The hole is for the emblem between the headlight buckets. This sticker is located inside the D/S fender right above the hole for the Egg Crate. The surface is certainly rougher on the backside.
I always thought the early vettes, pre 73 were fiberglass and then in 73 they were made from SMC. When I started to strip the body panels I began to wonder if I had a mixture on this car. Then I read how they seemed to increase the use of SMC year by year. I was hoping to use poly resin for the repairs on the nose since it's supposed to be a little more forgiving and less expensive. Being a novice at fiberglass and reading about repairs that simply peeled off has me a bit anxious so I was hoping to get somebody who knows what they are doing to confirm I have fiberglass...so far. I only have the front clip stripped at this point. Lots of sanding in my future. Lots of learning as well.
Thanks for the reply,
Mark
If you can't tell I'm having a hard time recognizing it since I have never seen SMC. I was 99% sure the nose was fiberglass, but I hate to assume things. I plan on going to the Corvette show at the Carlisle Fairgrounds in August. Hopefully I can get some good photos to use as references. A picture is worth a thousand words.
Thanks,
Mark
My 71 inside hood is somewhat smooth but gets rough, like press molded, on the edges where the hood mount frame is bonded to it. My front fenders are textured and are for sure press molded.
The rear of my 71 is much smoother all over and is for sure SMC.
I ended up spending more and buying Evercoat SMC Resin, Evercoat Panel Adhesive and Evercoat Mat because its compatible with both PM and SMC and gave me piece of mind in not having to do too much investigation on the part of the car needing repair and what material it is with the 71 being a hybrid.
I had repairs to do on both ends of the car so it was an easy decision for me.
I've used the Evercoat resin as well. But now (and for several years), for small jobs I just use home-center epoxy out of the syringes ...for a few bucks (the clear epoxy). Along with fiberglass hair if the job calls for it. It bonds both. I haven't had any come apart ...and I've definitely stress-tested it's strength. Just an idea.
...Mark G, how paintable are the epoxy repairs? I’m sure if you give a primer something to bite, it should be ok.
Very paintable. It seems to be the same stuff as the Evercoat epoxy you buy in a can (only smaller quantity). Most of the time I don't need a lot for a repair so that works great. You do the same type of bodywork as you would any polyester or bondo product.
Here is a dump of what I found in my research….. its from various past threads but you will get the idea.
Fiberglass
Genite = press moulded polyester
I know you know your stuff, GrandMaster, but SMC was and is, press molded, as far as Corvette panels were concerned. The first SMC panel was used in `71 and just happens to be that same rear quarter fender. All of the earlier versions of corvette fiberglass that fender came in, polyester glass(1968-69), Gennite 70-71, and SMC (71-73) were all press molded, but used different base materials.
"The general rule of thumb is that GM press molded 1968-72 Corvette parts with Mat and Resin compound and 1973-82 parts with SMC (Sheet Molded Compound) compound. Mat/Resin parts can be identified by the fiberglass strands appearing on the surface of the parts. SMC has a smoother, marble-looking appearance, and normally gray in color. Because some parts overlap both series of years, an example is 1969-82 Outer Door Skin, the part may only be available in one of the material compounds. Also GM Service Parts (replacement parts purchased through a GM dealer) for 1968-72 models were often times made using SMC versus Resin/Mat."
The first total SMC body was 74. The change over started in 69 with a transitional product called Gennite, made by General Tire and the first SMC panels were used on 71 rear fenders. The last panel to change was the 74 rear deck. But what do I know, I havent been doing this $h!t for but 38 years.
The `71 had a mixture of panels ranging from the old polyester to Gennite and the first SMC panel which was first used on the rear fenders sometime during the year.
68- All Polyester resin fiberglass, generally darker gray, black.
69- All polyester early with various shades of gray, black. Later 69 some doors made of a product of General Tire called Gennite. This product was similar to SMC and was a light gray.
70 - More Gennite panels used in different locations, more light gray panels used.
71 - A continuation of the trend to Gennite. The first SMC panels used, on late rear quarters. SMC panels had a marble effect and a light gray color.
72- More use of SMC for other panels, still a mixture of polyester, gennite, and SMC.
73- The trend to mostly SMC continues. The rear deck was the last polyester panel still to survive.
74 - With the change to the rubber rear bumper, the rear deck was redesigned, and the last vestige of polyester was gone. Even with all SMC there was varying shades of gray.
75- 82 All panels were the marble gray SMC. Still with varying shades of gray.
" In 1968 the Chemical / Plastics Division of the General Tire and Rubber Company introduced a low shrink wet resin system , known as Genite"..... General Tire became a major suplier of Corvette body components to the St. Louis assembly plant." " During 1970, another improvement in fiberglass technology, called low-shrink Sheet Moulded Compound (SMC), was introduced ..... The rear quarter panels on the 1971 Corvette were the first parts manufactured using this system."
Using the Evercoat product that works for both PM and SMC is such a wise choice. I don't want to spend a million bucks, but I certainly don't want to make repairs twice! Thanks for the advice,
Mark
Poly, SMC, or Both?
