1970 Corvette bumper washers

[Gerald A.]

The judging manual says the front bumper bolts are black oxide but not mention the washers. The AIM manual shows a flat and lock washer. Anybody who can tell me the finish on the washers would be appreciated.

[Gary B.]

Re: 1970 Corvette bumper washers

Gerald,

What are the part numbers in the '70 AIM for the washers? I'm guessing the lock washer is 103328. If so, you'll find some debate in the archives about the finish. I've looked for many months for an NOS example of 103328 lock washer and not found any. However, other lock washers with the same 103xxx GM part number prefix are dark gray, either from heat treatment or from a black phosphate treatment. I have therefore concluded that 103328 is the same dark gray, at least they were when new, some 40+ years ago. Which means the lock washers were not silver cad nor zinc.

Also, I believe there is consensus that the bumper bolts and the nuts for the early C3s are black phosphate. I suspect the "oxide" term in the black oxide phrase in the TIM&JG is not accurate, but nevertheless the black modifier accurately communicates the point that they were not silver cad/zinc.

Gary

[Bill L.]

Re: 1970 Corvette bumper washers

Gerald,

What are the part numbers in the '70 AIM for the washers? I'm guessing the lock washer is 103328. If so, you'll find some debate in the archives about the finish. I've looked for many months for an NOS example of 103328 lock washer and not found any. However, other lock washers with the same 103xxx GM part number prefix are dark gray, either from heat treatment or from a black phosphate treatment. I have therefore concluded that 103328 is the same dark gray, at least they were when new, some 40+ years ago. Which means the lock washers were not silver cad nor zinc.

Also, I believe there is consensus that the bumper bolts and the nuts for the early C3s are black phosphate. I suspect the "oxide" term in the black oxide phrase in the TIM&JG is not accurate, but nevertheless the black modifier accurately communicates the point that they were not silver cad/zinc.

Gary

Gary,

I concur with your findings. Even the thin flat washers appear to be plain steel or phosphate as well. The hardware that is phosphated or parkerized weathers in a very distinct manner when rust is not too prevalent as is the case on my 70 from Texas. If zinc was used I typically see it on the unexposed side of the hardware and none was evident on any of the bumper hardware.

Bill


Bill

[Alan S.]

Re: 1970 Corvette bumper washers

Hi,
When speaking of the "bumper bolts" finish, can we clarify if we're talking about the bolts from the brackets to the frame or the brackets to the bumpers?
Regards,
Alan