Bolt ID & size info please: GM 3779940 and Engine Asm "Production Bolt" on UPC C60-C1

[Scott S.]

I'm trying to identify two of the bolts used to secure the lower front AC Support bracket (C60-C1, Item 9, 3841697) on a 1967 small block.

First, the bolt used for the lower RH position as pictured in the AIM (or lower LH position if sitting in the car) is Item 8, GM 3779940. The bolt is listed under Group 7.874 referencing Gr. 1.073, but no dimensions are given. Does anyone know what the size, head type, Grade, finish and typical headmarks are for this bolt on a '67 SB?

The second bolt is located just above the first one, going into the same AC Support bracket. It is listed only as "Prod. Bolt & Washer". The only information I have been able to find so far on this bolt is for the 1964-66 Chevelle 8-cyl. AC compressor mounting, which appears to be very similar to the Corvette mounting configuration, shows this "Production Bolt" as being 3/8-16 x 2-1/4".

As with the first bolt, can anyone confirm (or correct) the bolt dimensions, and what is the head type, Grade, finish and typical headmarks for this bolt on a 1967 small block?

Thank you,

Scott

[Rich P.]

Re: Bolt ID & size info please: GM 3779940 and Engine Asm "Production Bolt" on UPC C6

Scott,

don't have my notes in front of me but here is what I do know. Those are the 2 bolts that attach the A/C bracket to the water pump. The lower bolt (#8 3779940) 3-1/2" long grade 5 black phosphate. Now here is the interesting part the top bolt can not be the original bolt from that location as the AC bracket is about 3/8" thick. SO it is my understanding that they used the "production bolt" from the lower spot that now has the new 3-1/2" bolt. That bolt is the production lower water pump bolt. So it would be grade 5 black phosphate BUT painted orange from the engine assembly. I forget off hand how long it is I think about 2-5/8" or 2-11/16". Both are 3/8-16.
So an original untouched 67 SB A/C car should have orange on the head of that bolt. I'd be interested to hear feedback on this.

Rich

[Scott S.]

Re: Bolt ID & size info please: GM 3779940 and Engine Asm "Production Bolt" on UPC C6

Rich, thanks very much for the reply. I am doing some more research on this, and will try to post back this evening.