Hi I am new to this forum and was referred to this forum by my buddy who spoke highly of this place. I have a 1990 C4 Corvette which I recently removed the beltline molding that runs the width of the car. There is an inch wide by inch and a half deep gap left that I need to fill. My question is how do I fill this gap so that it doesn’t lift, shrink, or alter in any way when it is done. These cars are made of a material called SMC apparently and need special techniques to complete. I am considering just buying new fenders and bumpers made of fiberglass without the beltline and to just fill that gap on those with fiberglass. I am hellbent on doing this project no matter how much time, money, and labor it costs me. I can include pictures in an updated post and I can even send in pics of the fender i sanded into. For anybody who knows what to do or has worked with C4 corvettes and can help, thanks in advance!
Although I am just an amateur, there are some amazingly talented people on this forum that have all the knowledge you could ever need!
After a quick google search, SMC looks to stand for Sheet Moulding Compound and is a thermo plastic hardener made using vinyl or polyester resin. This should make it easier than normal plastics to bond to???
Easier? If it was glass I wouldn’t be asking! I know the SMC parts are flexible, not rigid like regular fiberglass. I also don’t know if all the panels are made like this or if it’s just the bumpers and fenders because I can’t get behind the body pieces (yet) and see if they are more rigid or not. My guess is that the main pieces of the body are just fiberglass. I sanded down a ways into the fenders which are warped anyways, and there seems to be a plastic like material under the paint and gel coat. It’s almost like PVC. Hopefully someone in this forum is knowledgable and knows how I can permanently fill the beltline gap all the way around too. It’s somewhat deep, so that’s also a concern.
Vinyl ester resin can be bought with flex additive, the stuff I use has 10% flexion and can be bent considerably without damage. search the forum, there is info regarding what types of resin will bind to certian plastics. You will need to find out what type of plastic it is…
DURABOND 40/40
Drill some small holes into it to produce “rivets” and tape up the area away from the belt line and fill it.
Its gonna probably cost you a bit of money and Id be carefull about how you did it but it works.
I use that stuff on abs motorcycle body work to shave and fill holes in it. Like shaving and smoothing the turn signal pockets.
Should be easy enough and Ive never had it crack back out on me.
Ok. Any specifics on how to go about this? Consider me as someone who knows nothing at all. Your opinions, advice, and experience are all I have to go on. Where can I purchase Durabond 40/40? Should I lay a layer of fiberglass mat over the top of the filler you suggested?
You can get durabond at most any automotive paint supplier. Youll want to try to get yourself something bigger than the double tubes if you have a lot of area to fill or cover.
I dont know what your body is like but youre saying it is plastic (similiar to pvc or the like) with a composite covering.
If I had pics it would be easier but basicaly Ive filled up to 1/2 thick holes. Id probably try to make a reinforcement for it to help insure the long runs wouldnt have problems but Im seriously doubting youll have any problems at all.
So without pics or specifics…here is how Id speculate doing it.
Grind up the area with 36 grit so you have good biting areas. Rub down with denatured alcohol and compressed air to get ALL DIRT AND CONTAMINANTS OUT.
Mix the durabond up and paddle into the area and in about 5-10 minutes its rock hard. Sand down CAREFULLY and fill with glaze coat of bondo and youre done.
This stuff is like JB WELD but its meant for abs and other flexible car parts ie bumbers and stuff from the oem. A lot of shops are not great with ABS and wont send the bumpers to guys like me who have plastic welders…so they started using this.
I use it for filler. It sticks well and havent had a problem so far and Ive been using it for 7-8 years now.
There are two or three versions…I stay with semi rigid. Your mileage may vary.
Try ebay for cheaper prices and different sizes of it.
That was a great reply! Thanks! However I still have doubts as to what the body is made of. I’m guessing it is fiberglass because it is more rigid looking then the bumpers and fenders (which i ground into and found the “PVC” looking material which I am guessing is SMC. The only way I will no for sure what the body panels are made of is to ground into them. I will be uploaing pictures of everything soon. I may even upload the photo of how I want to get the car to look when I’m done. Give me a day or so. I am up to my neck in work, but I may have a short day tomorrow so I can grind into the body and upload the pics. Thank you!
Every Corvette ever made has fiberglass body panels.
Not trying to split hairs…
But there are a few exceptions.
Reynolds skinned a few C3’s in aluminum to try and sway GM to use their product instead of fiberglass.
Also, the hood of the new 'Vettes are made of carbon fiber, not fiberglass.
C5 and C6 have carbon hoods.
yup,
I have pics of the aluminum molds for the c6 hoods and they are pretty amazing. they were made a couple hours away from me by a company called marcc
well if its fiberglass or carbon the durabond is overkill…Just fill it with epoxy and call it a day.
okay. you say to fill the beltline with epoxy. can you recommend an epoxy to use that will not fall out of the beltline gap? the body is fiberglass, and i guess i will have to buy new front and rear bumpers made of fiberglass to make things easier and get the look i want. do i need to sand down to the fiberglass to get the epoxy to hold or just the gelcoat? also, what do i put over the epoxy once it is hardened and sanded to blend it into the rest of the body? thanks again!
Once you have the area cleaned and dry…use DYNAWELD by Dynatron #662.Its a semi-liquid paste mixed 1/1 by volumn,very easy. Sandable etc. About 20$ per 2tube pack.
Use clear packing tape as you go the length to back it up …it won’t perm stick to the epoxy.
Its adhesive and flex properties will do the job just fine.If you were to mix some milled glass fibers into it before troweling on…it would help in a few ways.Drying time will vary from a few hours to eight.
Sounds like you’ll need 8-11 packs.??
Cheers,Vinny
I would sand, drill some little holes, wipe with acetone, get and mix up fiberglass filled Bondo, tape off the lower line, apply and shurform the Bondo in the B stage. Repeat until slightly over the finish size and let it fully cure over night and then get to sanding to finish.
I wouldnt use the bondo to fill it Werk, bondo loves to shrink and crack on ya.
Ive shaved so many door handles its retarded and these days if I can I avoid it. It was always cracking back out.
Plastic door skins get durabond and steel doors get that lead/tin mix from eastwood.
I think he’s referring to short strand Dynahair made by Bondo brand ?In the green can. Its Polyester resin mixed with short chopped glass stands.
Vinny
The reason the reg. Bondo may crack or have problems it that when you apply it to steel, heat and cold they contract and expand at different rates.
Bondo is mostly PER (read the label) and FG is Glass and PER too…
Hey illshinkickz, I see you made it over here to ask about your C4 Vette body… cool. Most of these guys are very helpful here and Werksberg really knows his stuff. Not saying all the other people don’t. 
remember… i sent ya over here from autobody101.com forum