1972 Front Bumper Centre Support Assembly

[Mr. Cricket]

So true.
That’s what kill’s potential restorations. The finished article isn’t worth the cost involved.

Thankfully there are people out there that take their pleasure out of actually doing the restoration just not the finished result. I have a mate Dean that restores high end stuff but as soon as it's finished he can't wait to sell it more often than not at a significant loss

 

[Mr. Cricket]

Having done a bit of research, read all the pictures and documents (many thanks!) and spent half a day on Google I am now fairly sure that the 68/69 front bumper centre brace is different from the '70 onwards equivalent, hence the different part number. The main difference appears to be that the 68/69 part does not have the two holes on either side of the U that are used to mount the centre grille. From the pictures (courtesy of Corvette Pacifica) you can't tell exact dimensions but apart from the grille holes they look the same. Thus the later part can be used on the earlier 68/69 models but the 68/69 part can't be used on the 70-72 models, and why the later part tends to be called the 68-72 centre brace.
Here is the 68/69 ....
View attachment 29395

and here is the 70-72
View attachment 29394

Thus I definitely have the right centre brace because mine has the grille mounting holes. The mystery continues - more research is required.

Let me know if you need any more pics or even measurements

 

[TimP]

Let me know if you need any more pics or even measurements

That would be fantastic if you could - there are two dimensions which would really help me work out where the issue is.

The first is this one: The distance between the bottom of the radiator support and the leading edge of the front cross member that the radiator support sits on (the 'arrow' shaped one) on the centre line of the car. The dimension on mine is exactly 12cm.


The second is the distance from the leading edge of the front crossmember (as before) and the rear edge of the reinforcement bracket that goes across the nose of the car on the centreline of the car. The dimension on mine is just over 29cm.

Hopefully you can take these measurements on a fully built car but if you can't, not to worry.


Many thanks!

 

[Mr. Cricket]

12 & 28 cm checked the 28 three times with a square and a boat level

 

[TimP]

That's terrific - thanks very much for providing these measurements.

The first measurement is the same that suggests my radiator support is in the right place relative to the front crossmember.

The second measurement isn't a million miles out and is within the scope of adjustability, and at just over 1cm is still significantly less than the 3-4cm that the bumper sticks out by. I have deliberately set up my crossmember to be as far back as possible to try and get the bumper to fit properly. If I set up the crossmember to be the same distance from the front reinforcement as yours then the bumper would stick out even more......

So.... if the reinforcement rod that goes from the bottom of the radiator support to the front reinforcement fits ok (which it does) and the overall measurements are approx the same as yours it would seem to suggest that the basic geometry and dimensions at the front of the car are good, leaving the possibility that the centre brace is the wrong length, which doesn't seem at all likely. Or I'm being stupid somewhere along the line. ... which is distinctly possible.

Time for another think.......

 

[TimP]

Sometimes you can have mixed feelings about being right about something....

In my last post I think I suggested I might have been stupid somewhere along the line. Yessiree.

So all measurements looked ok against 'a know good' but still things didn't fit.

What had happened was that the front crossmember that sits under the radiator support was not quite at 90 degrees across the car. The drivers side end was about 3 mm closer to the rear than the centre and the passenger side was about 3mm further from the rear of the car. Thus the two ends of the crossmember were askew but the centre (where I did all the measurements) was in exactly the right place. Compounding this, the radiator was also a bit squiffy on the cross member thus magnifying the error. Once this was realised and straightened out, and the angle that the crossmember tips up at was set correctly then everything started to get a whole lot better. As an added benefit, I even can now get rid of a few shims that were sitting between the cross member and the radiator support.

Having done all this (and a few other things) the rear edge of the bumper now sits about 8mm from the front of the glass fibre. Is that about right?

 

[Mr. Cricket]

Much better Tim and it looks about right. Could be an optical illusion but your bumper seems to be drifting in toward the body. At either end of the bumper where it bolts to the body there should be a thick washer between the body and backside of the bumper which will even that gap up. Off to the garage shortly so will snap a pic of the gap and fixing.

 

[teamzr1]

At least from this photo angle, the point of hood bit off to matching point of bumper
and gap of bumper to hood edge on driver's side

 

[Mr. Cricket]

Washer



'Nose'

 

[TimP]

At least from this photo angle, the point of hood bit off to matching point of bumper
and gap of bumper to hood edge on driver's side

View attachment 29422

Yes - you are probably right - I will check and adjust tomorrow.

Thanks!

Tim

 

[TimP]

Washer

View attachment 29423

'Nose'

View attachment 29424

That's good to know. One of the things I had to do to fit the front bumper was to adjust the profile of the glass fibre where the bumper bolt goes through to ensure that both surfaces were parallel - I had had to rebuild both corners because they were damaged on arrival. I had considered using some sort of rubber washer or shim to make a more compliant join but if a metal washer/standoff was used then that's what I will do. Once they are fitted I will check that the bumper is sitting at the correct level and that the glass fibre and bumper edge are parallel all the way along.

Many thanks for taking these and the previous pictures - they have all been extremely useful.