1970-1972 hood support bolt headmark

[Chuck S.]

Re: 1970-1972 hood support bolt headmark

I would bet my lower two were either no plating or gray based on their condition...

Sorry, I omitted the finish thinking everyone was comfortable with those three being phosphate. Whatever the finish on top one, the other two should be the same (as Patrick pointed out)...same AIM item number (9), same part number (3846202), removed from the same bin, at the same time.

Dave, just for grins, have you ever removed the top hood support screw to see what the finish the rectangular washer has under the hood ledge screw? My logical mind finds it hard to believe that engineers would place a piece of natural steel and a natural fastener in essentially a "trough" to catch rain, wash, or melt off water. Not only would it obviously rust like a house afire, but it was also right in the face of anyone raising the hood...it wouldn't take long before a natural washer and screw looked really tacky.

Conversely, I don't believe those washers were zinc plated in 70; possibly later, but I've never seen that washer zinc bright in any 70-72, but I've never looked real close either. Terry's example clearly appears to have been either natural, or in my opinion, gray phosphate. Your example also shows to have much better corrosion resistance than natural steel; I think it would be premature to say it's natural...if it's natural, it must be one of those steel alloys that rusts to a protective patina of iron oxide (not really ; but it is well preserved like something gave it a headstart on the corrosion).

[Edward J.]

Re: 1970-1972 hood support bolt headmark

Chuck, I have the original plating on that square washer on my 72 coupe, it is zinc plated and fender bolt and 2 lower bolts are blk. phosphate.

[Terry M.]

Re: 1970-1972 hood support bolt headmark

Sorry, I omitted the finish thinking everyone was comfortable with those three being phosphate. Whatever the finish on top one, the other two should be the same (as Patrick pointed out)...same AIM item number (9), same part number (3846202), removed from the same bin, at the same time.
.

I expect to see a car in Florida (a 1972) that shoould solve the plating issue -- if one is willing to believe that 1972 finish is representative of a wider application. I might even be able to get some headmarks from it.

See now wasn't that clever that I didn't bound that with any years.

[Chuck S.]

Re: 1970-1972 hood support bolt headmark

...See now wasn't that clever that I didn't bound that with any years.

Remarkably astute of you...but then you've been doing this a looooonnnng time.

[Terry M.]

Re: 1970-1972 hood support bolt headmark

Yea, and I have F'ed up a lot of times too.

[Edward J.]

Re: 1970-1972 hood support bolt headmark

Patrick, is your 72 rectangle washer on the fender zinc plated? your cars is about the same time frame as mine.

[Patrick H.]

Re: 1970-1972 hood support bolt headmark

Patrick, is your 72 retangle washer on the fender zinc plated? your cars is about the same time frame as mine.

Based on my pictures I would say yes. I am not by the car, and don't think I will be in the immediate future.

Patrick

[Dave S.]

Re: 1970-1972 hood support bolt headmark

Sorry, I omitted the finish thinking everyone was comfortable with those three being phosphate. Whatever the finish on top one, the other two should be the same (as Patrick pointed out)...same AIM item number (9), same part number (3846202), removed from the same bin, at the same time.

Dave, just for grins, have you ever removed the top hood support screw to see what the finish the rectangular washer has under the hood ledge screw? My logical mind finds it hard to believe that engineers would place a piece of natural steel and a natural fastener in essentially a "trough" to catch rain, wash, or melt off water. Not only would it obviously rust like a house afire, but it was also right in the face of anyone raising the hood...it wouldn't take long before a natural washer and screw looked really tacky.
Conversely, I don't believe those washers were zinc plated in 70; possibly later, but I've never seen that washer zinc bright in any 70-72, but I've never looked real close either. Terry's example clearly appears to have been either natural, or in my opinion, gray phosphate. Your example also shows to have much better corrosion resistance than natural steel; I think it would be premature to say it's natural...if it's natural, it must be one of those steel alloys that rusts to a protective patina of iron oxide (not really ; but it is well preserved like something gave it a headstart on the corrosion).

Chuck,
Upon further review and a slight dis-assembly the bolt-washer and reinforcement plate look to be gray phosphate. Sorry for the earlier incorrect conclusion.
This car is a well kept original and even in spite of that the phosphate did not stand up very well. As you look at the upper plated bolts you can see how little moisture this car has taken. They are zinc or cad for sure.

[Dave S.]

Re: 1970-1972 hood support bolt headmark

Based on my pictures I would say yes. I am not by the car, and don't think I will be in the immediate future.

Patrick

Here are a couple of photos of 71 #21467. The fender reinforcement, bolt and pressed on washer are gray phosphate. Square washer is definately not plated. Notice the lack of a headmark and grade 5 slashes on the bolt. The plated bolts at the top are something resembling an EB headmark but are grade 5.
It may be that 72's used the plated square washer.
It's obvious from all these photos that gray phosphate was not very effective in stopping rust.

[Chuck S.]

Re: 1970-1972 hood support bolt headmark

Chuck,
Upon further review and a slight dis-assembly the bolt-washer and reinforcement plate look to be gray phosphate...

Dave, thanks for taking the time and extra effort to confirm the actual finish on a car that can be trusted to be original.

Your reinforcement plate is actually quite well preserved; in my opinion, plain natural steel, if exposed to water once, would probably be in worse condition after all these years. Something had to retard the corrosion for a few years...Since it has just a patina of rust, phosphate is the only coating that makes sense. If the same part was zinc or cad plated, as 72s could have been, I would expect the reinforcement plate to be virtually untouched; it would be a matte gray much like the hood support itself.

[D S.]

Re: 1970-1972 hood support bolt headmark

My 1970 has all anchor headmarks as far as I can see. As I re-read through all of the posts here I see more proof that the line workers used whatever screws and bolts that was at their disposal and all that mattered was getting the vehicles finished.
Does anyone know the size and thread of the screws or bolts?

[Terry M.]

Re: 1970-1972 hood support bolt headmark

My 1970 has all anchor headmarks as far as I can see. As I re-read through all of the posts here I see more proof that the line workers used whatever screws and bolts that was at their disposal and all that mattered was getting the vehicles finished.

[/i]Just what I told you back on the 12th[i]

Does anyone know the size and thread of the screws or bolts?

Take yours out and measure them. That is what I would have to do.

[D S.]

Re: 1970-1972 hood support bolt headmark

Take yours out and measure them. That is what I would have to do.

I'm going to have to remove the one in the gutter anyway. All this lead to the discovery that the rectangular "washer" or backplate is MIA.

[Chuck S.]

Re: 1970-1972 hood support bolt headmark

...As I re-read through all of the posts here I see more proof that the line workers used whatever screws and bolts that was at their disposal and all that mattered was getting the vehicles finished...Does anyone know the size and thread of the screws or bolts?

Mmmmm...Well that thought conveys the vision of line workers scrambling around to find something, anything, that would fit, and that definitely was NOT the case from my observations.

At the station where the hood support, release cable etc were installed there were bins with the assigned parts and fasteners to be used. They had people that did nothing but restock those bins with the proper fasteners and parts by part number. I have considered what would happen, aside from a severe a**chewing, if a bin were allowed to go completely empty, and perhaps cudda' mighta' observed where a substitution was made, but in general, I would say substitution seldom happened. That's not to say that the people using the fasteners or restocking bins cared about what headmarks were so long as they were the right GM part number.

Sizes: The top two zinc plated machine screws are 1/4" NC X 5/8" long, with integral cut lock washer (mine apparently had two different Anchor headmarks; haven't investigated to see the difference). The three phosphate self tapping machine screws on the fender are 5/16" NC X 7/8" long, pointed ends, with integral flat washers.

[D S.]

Re: 1970-1972 hood support bolt headmark

Thanks for the size and information, Chuck. My choice of words to describe the assembly line process was not accurate. Specifically, given all of the different headmarks as evidenced in print and photos here does support that more than one manufacturer supplied correct parts and that they were even mixed on the same vehicle. Either one station did one function with a set of like screws and then another station performed a separate task on the same thing with another set of screws or one station had mixture of correct screws with different headmarks to perform the whole task.