Hey guys, I've recently found a used 1978 front and rear stock bumper cover for a very cheap price. I have cleaned and preped everything on the car and I am all ready to install on my '75. Now, I just dry fit the bumper cover, and i know it will need some massaging into place, but it feels like it is going to have no shot at lining up to the body lines.

Any tips you guys have as to which blots to start with as I work it into place, or other pointers to get it lined up as closely as possible.

 

I, too, put some new bumpers on my '75 recently. I used a set of flex fiberglass units. They still need final fitment, but I was able to get them close to where they need to be. I'll definitely need to do some filler in a couple spots.

I'm sure others with more experience will give advice. For me, I got the center lined up on the front first. Then worked outwards. The sides are where the massaging will have to happen.

I don't know if it's an issue when fitting stock urethane, but for me, I had problems getting the lip at the top of the front bumper over the lip of the metal bumper support. There wasn't enough give in the glass bumper to get it up over that lip and into position. I was going to end up breaking something, so I got out my grinder and took most of the lip off the metal bumper support. About 1/4". Repainted it, then fit the bumper cover and it slid right into position.

The rear bumper lined up decent on it's own.

 

IF you want the body lines all to match perfectly, like they should, you might as well just face the fact that major bodywork is likely. Maybe you will get lucky. I chose to use Truflex because my painter pushed it as the best choice, but if I could do it again, I would buy straight fiberglass, and possibly build it up on the inside to increase thickness. Problem with Truflex, and maybe even straight fiberglass bumpers, is they are too thin. Result is that even if you get all the body lines to match up, the overall bumper still will have waves and distortion simply because they are too thin. Bottom line for me is that the front and rear bumpers should be as thick, and look as straight as the rest of the car, and after expending lots of my dollars to my painter to get body lines to be perfect, they still have more waves and distortions than the rest of the car. Its better than rubber, but not as good as the rest of the car.

I recommend buying pure fiberglass bumpers, and if they are not as thick as the rest of the car, add layers of glass on the inside to make them so....THEN, plan on lots of sanding, possibly cutting and adjusting, bondo, etc to make them the way GM should have made them from day one. I certainly cannot look at original rubber bumpers and fathom how GM was okay with that, or how any guy buying a brand new Corvette in 1977 could accept it......but, thanks to our US Government and their silly 5 mph crash protection laws, that was the outcome and your only choice. It certainly would not pass in a car show.

 

The best thing I can tell you is to buy a new set of the front and rear retainer strips. If you're trying to reuse a set of used retainers, they're probably missing a few studs, and likely bent in a few spots. Urethane bumpers need the retainers, to insure that even pressure is applied all the way around the bumper's mounting surface.

The cheaper "T" bolts that Corvette vendors sell, will work fine with the fiberglass bumpers, but not with original urethane bumpers.

If the bumpers you bought have been sitting around off of a car, for any amount of time, they've probably lost their shape some too. Once they get out of shape, especially if they've been laying flat somewhere, or had something laying on top of them, they are very hard to get back to they're original form.

When these cars were new, the urethane bumpers looked good. They fit well, and didn't have any waviness to them.

40 years have passed since these cars, and their bumpers, were new. In spite of what most owners of these cars want to believe, very few of these old cars have virgin un-hit bodies. Most old Corvettes have had some kind of body work done to them, even if it was only sanding during a repaint, that can effect the fit of bumpers.

To properly perform the job it was designed to do, the urethane bumper covers, needed to be soft and flexible. By nature, any soft material is going to sag, if it doesn't have some kind of support under it. Unfortunately, to fully support the underside of the bumper cover, would likely have hindered it's ability to function as a flexible cover.

Today's flexible bumper covers are much better, but they've benefited from 45 years of development. When the Corvette first came out in 73, with it's flexible urethane front bumper cover, it was brand new technology. When the 73 Corvette came out with it's urethane bumper cover, and the 73 Pontiac Grand Am and 73 Chevelle Laguna came out with similar covers, it was considered quite revolutionary.

 

I'm going to reuse the old mounting brackets, only 1 stud bent on me during removal so i grinded it off and drilled it out. The rest are fairly straight. The brackets have all been sanded and painted with 395a and look like new so i have no concerns re using them.

The bumper covers i purchased were off of a parted out 78. They retained the correct shape and appear very good. My issue is on the width. Stretching and pulling them to line up close with my lower rear fender seemed challenging last night at midnight. I have my father in law coming tonight to help me fit it into place. I suppose I will start at the top center and work our way out. Would it be of any benefit to attach in the taillight cups to line those up and then work our way out from there?

Would a low power heat gun help with ply ability without damage to the cover?

As I have stated in my build post, these classic car tasks are all new to me so I'm being very cautious and trying my best to do things 100% correct with no damage to orginal parts.

Thank you all for the help so far.

 

Rear bumper is fully installed. I'll uldate here incase soneone searches for this in the future. Basically the cover dry fit around 1 inch to small on each side. I started at the top and worked my way out tightening the brackets just hand tight. I had a couple spots on the top where i needed to use a floor jack and a thin piece of oak to gently lift the bracket to a flush level before fully tightening.

The top looks great but the sides stil are a bit off. My next step will be to let the car sit in the sun for a day to get some more flex into the bumper cover. I will then loosen and tweek for the last 1/4 to 1/8 of an inch gap on the sides.

I'm really impressed that it conformed as well as it did. Thsts fir the hello snd hopefully someone in the future can use this thread.

Up next is the front bumper cover.