My 80 needed bumper, so I ordered flex fiberglass bumpers. I installed them last September and molded in the front one with regular fiberglass resin. The same resin I have used on all my vettes with pout any problems. Well I decided to mold the rear one on this spring before I painted the car. Wel for this job after reading about resin on the forum I decided to use the correct resin for the SMC panels. As I was finishing up the body work I noticed a crack on the drivers side front bumper. After sanding awhile I just ripped up the fiberglass. Not the resins fault but mine. I didn't rough up the surface enough. Well on that side I used the correct SMC resin. Then I finished up all the body work and painted the car.
Well I started to buff it out and noticed ghost lines on the rear bumper. Well what it turned out was shrinkage in the body work. I argued against it in another thread but that is what it was. I apologize to the members that I argued with. Then I buffed out the front bumper and got a ghost line or shrinkage on the side of the front bumper that I had to do over with the SMC resin. I left the car sit all summer in the New York heat and I guess it has finished shrinking. I got some of the shrink lines out by wet sanding, but there are a few spots where you can still see it.
But I noticed that thought all of the problems the side of the front bumper that I used the regular resin on was perfect. Why do you think that is. Well any way I have to redo the rear bumper and the side of the front bumper that has the SMC resin on.
I have always used regular resin on the vettes I have owned and never had a problem. I think I will stick to it.