I am a new memeber to corvette forum but have been in this site reading and learning from you all for a couple of years now, Thanks. I have a mix match C3 that I have been working on for the past Two years. this car sat in my dads drive way on blocks for 18 years and due to his health he only could bore us kids with his plans and dreams for this car. I decided to make his dream come true. its been a long, exspensive, but rewarding project for me and letting my dad know were I am at with this project keeps me motivated. I have replaced everything on this car, and am working on getting it repainted. I have stripped the car down to the fiberglas, and have removed averything from its body, 2 steps forward 1 step back. I think I should of done this part First. I am about to start spaying the 2k primer that I have purchased from a local body shop. I have many questions going foward but I will start with, is it ok to prime the Urathane bumpers the fiberglas body, the head light metal and the aluminium grills with the same type of primmer?

 

Others can chime on this however the flexible pieces need the flexible additive added to the primer for those parts. Have fun!

 

If you are using a quality polyurethane paint system, there really shouldn't be any need to add a flex agent with todays paints.

Its a good idea to first seal the fiberglass/SMC with epoxy before you shoot your 2K. It would help if you specified what primer and paint you are using.

 

the primer I have bought is MAXX FILL 2K High Build Urethane Primer Surfacer w/ Activator I am not sure of the paint brand yet but i will be getting it from the same local body shop so it should be compatable. I was not aware of the Epoxy and the body shop didn't try to sell me any. what does the epoxy do for me?

 

It's a 5 Star product, they certainly do not define "properly prepared fiberglass surfaces" very well, and you need to use their etching primer on metal parts prior to applying this surfacer. I'd call their tech line and tell them what you are shooting, SMC and or fiberglass?

http://www.autobodybrands.com/primers/5453.htm

 

You did not mention year, but since you have urethane bumpers, you have an SMC body. The Maxx Fill 2k primer is not recommended for SMC according to the 5 Star tech sheet. The 5 Star XTreme Original Primer #5885 is recommended for SMC. Unless you call the tech line and they say Maxx Fill is okay for SMC, I would not use what they gave you. A standard 2k primer like these will work over your body, but epoxy offers some advantages, although at a higher cost.
Epoxy is arguably a more durable foundation for the first paint to go over the bare glass/smc after major repairs with mat and resin have been completed. Epoxy has more advantages over steel, but it does offer better adhesion and moisture resistance over either surface. If you need to use body filler, it can be applied over the epoxy primer. You can apply a compatible 2k primer over epoxy for block sanding.
Production work in a body shop does not call for epoxy due to cost, it's more of a high end or restoration product but the masses will agree on it's use for restoration work and durability.
Your bumpers should be checked to see how brittle they are before you spend the money on refinish materials only to have the bumpers crack once you start driving the car. Check on the bottom and bend a small piece. If the plastic flexes you are probably okay for a while, if the piece breaks off, you'll need new bumpers. If you plan to keep the car, you want the bumpers to last as laest as long as the paint job. It will be harder to replace them after your car is painted.
If you do paint them, and the surface is paintable, there are primers specific for use on urethane bumpers such as Transtar Waterborne Flexible Primer. Base coats generally don't require flex agent, but some urethane clears cure very hard and could crack. PPG Concept for instance can be used with flex agent or 1/2 the hardener can be used. If you paint the bumpers off the car, you will need flex agent in the clear for assembly.
Iron out your primer choice so you know which paint line to go with and make sure you use products that are compatible with your surfaces and with each other.

 

If you download the Tech Manual, it has all of their tech sheets and info on all of their products, it 50 pages.

 

Thanks Al, and a nice write up for the OP.

 

Thank you sir. I'm not questioning your response on additives but I always thought the clear remained somewhat flexible also until I needed a mixing cup one day and found one with cured Concept 2002 Clear in it. I removed a chunk from the bottom and it was so hard it took pliers to break it and the thin skin on the edges just broke away. It would work until the bumper was flexed, then I'm sure it would crack. Other clears might be different. No, I did not reuse the mixing cup.

 

I agree, they are all different. I have my bumpers in SPI Universal clear and they still seem pretty flexible. SPI said I didn't need any flex additive, and so far so good. I know a few guys who shoot PPG products, and they skip the flex additive as well. I don't know enough about PPG clear to make any judgements though.

BTW Al, Happy New Years.

 

thanks guys, as for the year of the C3 its a very much mix match, its title as a 1976, but its a convertable, the front clip is of a 1980, an the rear bumper cover is a 1980, the intire interior including dash is of a 1978 with a 140 mile hour speedometer which I was told was unique. The frame has the exhast hole wich pertains to a certian range of years but i cant remember. over all the car appears to be a 1980 convertable.