1972 Front Bumper Centre Support Assembly

[TimP]

Does anybody know if the bumper centre support assembly (see picture below) is different for the 1968/69 models and for the 1970-72 models? I have a feeling they might be as they have different part numbers - (203107 for the '68/'69 and 3963129 for the '70-'72) but that doesn't always work.

This might solve a problem I am having at the moment as when I try and fit the front bumper it sits proud of the front of the body by about an inch and quarter. the chassis extensions, cross member and rad support all seem to be exactly where they should be. I have checked against some stock photos. Even the rod that goes from the lower middle of the radiator support to the front tip reinforcement fits well suggesting that the basic alignment is good, but there is still a massive gap.

Any help much appreciated!

 

[Mr. Cricket]

Been a while since I had mine out but from memory that looks different to my '71. I'll see if I can get a pic

 

[teamzr1]

I cannot recall the exact year but early 1970s the feds here required front bumpers must handle more of a crash load so
so Corvettes had to make structure changes for that mandate
Others here would know better than I

 

[Mr. Cricket]

Not easy to get pics of but seeing it was pretty darn dirty back there I took the number plate bracket off and ctr grille out so I can clean up.

I'd say they look different

 

[teamzr1]

Attached below I got from GM engineering as PDFs
the design specs for 1969 and 1972
You may have to read them closely and see if the specs helps
Each is about 160 pages

 

[TimP]

Not easy to get pics of but seeing it was pretty darn dirty back there I took the number plate bracket off and ctr grille out so I can clean up.

I'd say they look different

View attachment 29381

View attachment 29382

Many, many thanks for taking the trouble to take these pictures - they are extremely useful. I would agree this looks different from the one I have. I will compare these closely and see where they differ, there might be some dimensions that I can derive from the other components that would give me a clue as to what I need to do.
Once again, many thanks - appreciated.

 

[TimP]

Attached below I got from GM engineering as PDFs
the design specs for 1969 and 1972
You may have to read them closely and see if the specs helps
Each is about 160 pages

These are terrific - thanks for posting them here. Lot's of good stuff in these - fantastic and really useful! Many thanks.

 

[TimP]

I thought this might be a problem that I introduced in the rebuild but looking at the photograph of the car on delivery, there's clearly a big gap on the (fairly well perforated) bumper when it arrived.

 

[Mr. Cricket]

I thought this might be a problem that I introduced in the rebuild but looking at the photograph of the car on delivery, there's clearly a big gap on the (fairly well perforated) bumper when it arrived.
View attachment 29385

Yeah that aint right Tim. How big was that bird that crapped on the garage roof

 

[teamzr1]

These are terrific - thanks for posting them here. Lot's of good stuff in these - fantastic and really useful! Many thanks.

Your Welcome Tim

Closely go through as the pages as lots of that year C3s design detail in those PDFs

 

[Nassau65]

I thought this might be a problem that I introduced in the rebuild but looking at the photograph of the car on delivery, there's clearly a big gap on the (fairly well perforated) bumper when it arrived.
View attachment 29385

Never seen a chrome bumper vette look like that on the front, something is definitely not right there.

 

[teamzr1]

Sure looks like that front ass ended a vehicle and right trim around light broke and crown of bummer bent downward ?

 

[TimP]

Yeah that aint right Tim. How big was that bird that crapped on the garage roof

Seagulls! Probably a youngster judging by the size of it, if it had been an adult there would just have been a large hole.

 

[TimP]

Never seen a chrome bumper vette look like that on the front, something is definitely not right there.

The reason it looked like this was that almost the entire reinforcing structures for the glass fibre front end had corroded away. There was no front cross member (the arrow shaped one at the front) just two stubs where it bolted on to the chassis extensions, the reinforcing bracket that bonds to the underside of the front clip to support the headlight pods had almost completely disappeared (which is why they have almost fallen through) and the whole front end wobbled alarmingly when the car moved. it's one of the reasons why there is a gap between the leading edge of the hood and the rest of the bodywork - there wasn't anything to support the very front of the car. I was very lucky that the glass fibre didn't completely crack up in transit when the car crossed the Atlantic.

It's all fixed now though. The mystery of the bumper centre brace is the last piece of the puzzle.



and the centre brace, sitting much too far forward....

 

[Nassau65]

You’ve certainly done a marvellous job, I’m sure your sort it out.

 

[TimP]

Sure looks like that front ass ended a vehicle and right trim around light broke and crown of bummer bent downward ?

View attachment 29386

I'm pretty sure that the front end hadn't suffered any impact damage just severe corrosion. The rear was damaged before it left Los Angeles as the original pictures show the rear passenger side bumper at a strange angle. I subsequently found cracks in the bodywork just beneath the luggage rack on the same side when I came to strip the paint in that area - so it clearly had a bump there at some point.

 

[TimP]

You’ve certainly done a marvellous job, I’m sure your sort it out.

Many thanks. It's getting there. Road legal by July this year.

 

[Mr. Cricket]

Fantastic job. If you'd paid to have the work done it'd be £100k and worth 40 to 50k

 

[Nassau65]

Fantastic job. If you'd paid to have the work done it'd be £100k and worth 40 to 50k

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

 

[TimP]

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 ....


and here is the 70-72


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