Finish for bolt GM 9416253

[Gary B.]

I’ve searched the TDB archives and Google and found no information about bolt GM #9416253, which is used in ‘66 and ‘67 to attach the shifter mount to the crossmember (item #3 in AIM image). The repro bolt I bought is bright zinc, but nearly all of the repro nuts, bolts, and washers for the shifter and transmission mounts are incorrect bright zinc, I’m suspicious about the bright zinc for the repro if 9416253. Does anyone have direct knowledge about the finish for the GM bolt?

While I’m focused on that area of my restoration, can I also get confirmation that bolts GM 9419073 (item 5 in AIM image) and 454933 (item 9 in AIM image) are both black phosphate? That’s what I read in the archives. Those two bolts came as bright zinc in the repro kits I purchased.

Thanks,

Gary
5A4D013E-E460-4E77-A4DE-B5372BAFC057.jpg

[Page C.]

Re: Finish for bolt GM 9416253

Hi Gary
The GM Engineering Standards indicate the 9416253 as a 3/8 x 16T x 1 1/8 with a cadmium finish and is a grade 8. The 9419073 was a 7/16 x 14T x 1 with a phosphate finish and is a grade 5. The 454933 was a 7/16 x 14T x 1 1/8 in length with a plain finish and a grade 8

[Gary B.]

Re: Finish for bolt GM 9416253

Page,

That’s great information. Thanks

i think the GM spec’ed plain finish for 494933 vs black phosphate reported by some people is due to the fact that a plain finish can look quite dark gray, almost black, easily mistaken for black phosphate, as Joe Lucia showed us a few weeks ago in a posting he did that was all about fastener finishes. Another example of a very dark, plain finish is lock washers in the series 1033xx, for example, the 103328 hi-collar lock washer that is used at many locations on 66 and 67 Corvettes. And lick washer 103321, of which I have an NOS example, which I believed was black phosphate until I was informed that the GM finish was given as plain.

Gary

PS I have to say this forum is fantastic, because of the people who take the time to help each other.

[David B.]

Re: Finish for bolt GM 9416253



I would be cautious with this conclusion!

[Gary B.]

Re: Finish for bolt GM 9416253

David,

Cautious about the conclusions for the finishes given? Or for the people? Or both?

Gary

[Ronald L.]

Re: Finish for bolt GM 9416253

The GM specifications are the standard and undisputable.

Page - can I have the book you're looking at when you tire of it? I left mine on my desk back in the fastener engineering HQ in 1984...

Gary - regarding dark finishes, if a bolt is grade 8 - you will not find it phos treated, hydrogen embrittlement type issues. As well, you won't want any Boron steel bolts as they don't survive salt climates. Usually a grade 8 bolt, once hardened, oil quenched and stress relieve annealed is going to have some level of resistance to oxidation. Again, unless it was a Special Fastener, the GM Standards Book is the gold standard for what went on these parts.

[Gary B.]

Re: Finish for bolt GM 9416253

Ron,

So, I guess I need to be cautious of the people...

Gary

[Page C.]

Re: Finish for bolt GM 9416253

The GM Engineering Standards list 13 different plated and coated finishes for externally threaded fasteners: They also list the finish for a Plain Finish as followers:
Hexagon Bolts: Plain finish steel bolts shall be clean (free from dirt, rust and die or drawing compounds) and unless otherwise specified by user, coated with a light oil film.

[David B.]

Re: Finish for bolt GM 9416253

David,

Cautious about the conclusions for the finishes given? Or for the people? Or both?

Gary

Last couple of comments re: Standards are well stated. Keep judgement of people out of the equation.

[Joe L.]

Re: Finish for bolt GM 9416253

The GM Engineering Standards list 13 different plated and coated finishes for externally threaded fasteners: They also list the finish for a Plain Finish as followers:
Hexagon Bolts: Plain finish steel bolts shall be clean (free from dirt, rust and die or drawing compounds) and unless otherwise specified by user, coated with a light oil film.

Page------


The fasteners I pictured in a previous thread were known NOS examples of GM part numbered fasteners which GM specified as having a plain finish. None of them even remotely appeared like oiled raw steel. There's no judgement call or opinion involved here, at all.