Bolt Part Numbers- Size and Finish

[Grant W.]

Re: Bolt Part Numbers- Size and Finish

From this info then all bolts attaching the bumpers should be black phospahate and none should be cad or zinc is that correct? I thought I had read the ones attaching to the bumper side of the brackets should be cad and that corresponds to the different number 9419077 which is the bolt that attaches to the bumper vs the 9419075 which attaches to the frame. Why would they use two different part numbers for the same bolt.
Thanks
Sheldon

Hi Sheldon

In the pic is Black phosphated bolts with the serrated washer. Those attach to the rear bumper brace that attaches to the frame. The bolts and lock washer and nuts are zinc plated.(it maybe for your year the bolts and lock washer and nuts black phosphated.

Head markings could be blank and 3 lines, L , or 3 lines and a square. My 68 had the RBC. Maybe yours could have the same.

Rear bumper bolts that bolt the back rear bumper are zinc with the large A head marking, Washer and I think but not sure lock washer is zinc plated. The bolt that bolts the front side of the rear bumper to the bumper bracket from the frame is Black phosphated and maybe the nut too. My bolt was black phosphated and nut was zinc. (my car is a 68)

All the front end bolts, washer, lock washer and nuts including the RSC bolt that bolts the front bumper brace to the Horn frame is Zinc plated. Your bolts that bolt to the Horn could be Black Phosphated and including the nut. The head marking maybe an L, or just a square, maybe TR and A's. All other bolts should be zinc plated.

Anything else??? Gotta go. Gonna watch the Olympics on TV. I don't have tickets but the company I work for Fresh Point Food service have supplied food products to GM Place. 4 hours of sleep in the last 2 days.
I missed the torch parade as Mr. Steve Nash was running with the torch. Right in front of our house.

Arnold was in town too running with the Torch. Funny thing is he has a house on Okanagan lake where my step mother has a house on the lake. He is 4 miles down the lake only but only can get there by float plane.

Well I hate to brag but a friend of ours got chosen to run the torch. Here I am holding it. I will also have a big smile when I finish my car....Its been 10 years now.

Thanks, grant

[Chuck S.]

Re: Bolt Part Numbers- Size and Finish

...
941075 is the 4 bolts that hold the center bumper brace to the front bolt in cross member. These bolts are fully visable with the hood open...

If 941(9)075 is cad plated, why would they use it to attach black painted center brace to black painted cross member in plain view?...Wouldn't they be trying to "hide" the fasteners in a black background by using black phosphate, rather than accentuate them by using a silver finish on black?

But, then, 941(9)077 is the bolt that attaches the rear bumpers, and that's the one that Edward is claiming is zinc. Maybe aesthetics didn't matter up until 71-72, and then there was an apparent effort to hide the fasteners on the rear bumpers by using zinc on chrome?...

Or, maybe it's not aesthetics at all, but corrosion resistance that was important. So that would mean both part numbers are zinc plated, but some locations apparently also use a black phosphate fastener of the same part number??!

Sheldon...If you can make any sense out of this thread, then use that!

[William H.]

Re: Bolt Part Numbers- Size and Finish

Chuck

This was very interesting. Did you ever come to any final conclusions? I'm trying to make sense of my '68 for front and rear bumper bolt hardware finishes. Thanks for your help. Bill

[Bill L.]

Re: Bolt Part Numbers- Size and Finish

HI Shelden,

I am going through this exercise on my 70 also. Mine is a Texas car and is very well preserved. I could find no rear bumper hardware that appeared to be zinc or CAD plated. Typically I can see remnants of zinc on bolts when removed and not one of the rear bumper bolts showed any zinc remnants. The head marks are all either A or M with one oddball that I suspect may not be original because the flat washer was missing. A bit of the zinc is clearly evident on the tire carrier long bolts so I used them as a starting point to compare for remnants of zinc on other hardware on the rear section.

Same is true for head markings on front bumper. I have not removed the hardware to inspect it closely for finish just yet.

I reviewed my findings with the owner of one of the best corvette shops in the country and he concurred with my thoughts.

Other Hardware is going out to be zinc plated where needed. I was going to try at home but another corvette owner is sending his out and it is going to cost me about $20 for the few pieces I have to do in zinc by working in with his stuff. I will try and phosphate at home thanks to Grant.

Not definitive but hope this helps.

Bill

[Sheldon S.]

Re: Bolt Part Numbers- Size and Finish

I am away from home right now and don't have the info in front of me. What I think I determined was that the bolts that bolted to the bumpers were zinc or cad plated, although the flat washers and lock washers were black phosphate. I don't think it was a visual thing but more on the corrosion aspect. In the AIM the bolt that bolts to the bumper is one part number and the other bolt does not bolt into a chrome plated nut. maybe it was felt that a zinc plated bolt bolting into the nut welded onto the bumper that was chrome plated wound not rust as easily as a black phosphated bolt???? Not sure if I have explained this very well or not. But on my car that is what I did.
Sheldon