69 front bumper alignment problems, suggestions please
Thread Starter
Burning Brakes
Joined: Mar 2006
Posts: 915
Likes: 2
From: Lima, OH -- 69 L71 427/435hp
69 front bumper alignment problems, suggestions please
I have a 1/2" gap around the center and 1/4" at the ends and I'm at a loss.
I have adjusted the license plate support far back as it will go, as well as moving the frame extension far back as it will go, and still no luck.
I am using all the original equipment, which is why I don't understand what's going on here.
I do not have the radiator support in yet, but would the brace from the nose to it effect the alignment?
Also, I still am not sure what bolt is supposed to be used in the frame extension and/or if this up/down adjustment makes any difference?
Open hole to rear on frame extension
The only other thing I have thought of, which 'could be' a 'minor' problem, is the fact I used POR-15 on all the parts, which may have a millimeter or two extra thickness affecting the diamater of the holes, 'possibly',...but I don't think it would throw the adjustment off this much.
Any suggestions would be appreciated, this bumper is becoming a real eye sore.
Thanks
I have adjusted the license plate support far back as it will go, as well as moving the frame extension far back as it will go, and still no luck.
I am using all the original equipment, which is why I don't understand what's going on here.
I do not have the radiator support in yet, but would the brace from the nose to it effect the alignment?
Also, I still am not sure what bolt is supposed to be used in the frame extension and/or if this up/down adjustment makes any difference?
Open hole to rear on frame extension
The only other thing I have thought of, which 'could be' a 'minor' problem, is the fact I used POR-15 on all the parts, which may have a millimeter or two extra thickness affecting the diamater of the holes, 'possibly',...but I don't think it would throw the adjustment off this much.
Any suggestions would be appreciated, this bumper is becoming a real eye sore.
Thanks
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
I have the same gap problems on mine also. I think they make shims to correct the gap but I have never done anything about it just yet. Hopefully someone else will come along and give us both some good advice on how to correct these gaps.
Le Mans Master
Joined: Oct 2005
Posts: 9,429
Likes: 44
From: Macon, GA
That is a very common problem with all steel bumper cars. I fought with my front bumper for 3 solid days before I got it right. I had to bend the bumper very carefully to make it fit. I also had to shim the bumper extensions on each end and the center nose brace to make up for the difference. I doubt that the POR-15 has added that much thickness to the metal that it is throwing it off. I hate to say it, but you're just gonna have to dive in there and make it work. Good luck. 
Thread Starter
Burning Brakes
Joined: Mar 2006
Posts: 915
Likes: 2
From: Lima, OH -- 69 L71 427/435hp
That is a very common problem with all steel bumper cars. I fought with my front bumper for 3 solid days before I got it right. I had to bend the bumper very carefully to make it fit. I also had to shim the bumper extensions on each end and the center nose brace to make up for the difference. I doubt that the POR-15 has added that much thickness to the metal that it is throwing it off. I hate to say it, but you're just gonna have to dive in there and make it work. Good luck.
What is the acceptable tolerance for factory gap? In other words, what is it supposed to be?
The bumper did not have shims when I took it off, and if I shimmed the ends out to create a 1/2" gap all the way across to appear 'even', I think that big of a gap will look like crap.
Le Mans Master
Joined: Oct 2005
Posts: 9,429
Likes: 44
From: Macon, GA
So your gap was very close to start with?
What is the acceptable tolerance for factory gap? In other words, what is it supposed to be?
The bumper did not have shims when I took it off, and if I shimmed the ends out to create a 1/2" gap all the way across to appear 'even', I think that big of a gap will look like crap.
What is the acceptable tolerance for factory gap? In other words, what is it supposed to be?
The bumper did not have shims when I took it off, and if I shimmed the ends out to create a 1/2" gap all the way across to appear 'even', I think that big of a gap will look like crap.
It sounds like your bumper is "bent" too much. Meaning the "V" is too tight. Is that what you're saying? If so, you may be able to slowly work it back out without cracking the chrome. Also, the center brace as well as the outer braces are adjustable though you probably already knew that. Do you have any pictures you can post?
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
1ARACE,
The factory spec on the gap was .48 to .52. (UPC 11-13 in the assembly manual)
So, your half inch gap at the center is correct, the ends just need to be shimmed out a quarter of an inch or so.
I had the same problem installing an original bumper back on my 72. I had to carefully bolt the ends in place and then use longer bolts for the center to pull it in to place. Once this was done, I then loosened the bolts on the ends and pulled outward and inserted shims. It was not easy, but it worked.
I don’t think the coating you used would have played any part in how the bumper fits on the car and I don’t believe the center rod is going to make a difference either.
The outer brace used a shim GM p/n 3711834 and they went between the bumper and the fiberglass. There were no shims used in the center. I have a picture of this at this link. The shims are number 15 in the upper left hand corner.
http://willcoxcorvette.com/product_i...ducts_id=24430
Willcox Inc.
The factory spec on the gap was .48 to .52. (UPC 11-13 in the assembly manual)
So, your half inch gap at the center is correct, the ends just need to be shimmed out a quarter of an inch or so.
I had the same problem installing an original bumper back on my 72. I had to carefully bolt the ends in place and then use longer bolts for the center to pull it in to place. Once this was done, I then loosened the bolts on the ends and pulled outward and inserted shims. It was not easy, but it worked.
I don’t think the coating you used would have played any part in how the bumper fits on the car and I don’t believe the center rod is going to make a difference either.
The outer brace used a shim GM p/n 3711834 and they went between the bumper and the fiberglass. There were no shims used in the center. I have a picture of this at this link. The shims are number 15 in the upper left hand corner.
http://willcoxcorvette.com/product_i...ducts_id=24430
Willcox Inc.
Last edited by Willcox Corvette; Jul 17, 2007 at 10:44 PM.
