Need help with C2 fuel pump bolt identification

[Rick B.]

Hope everyone is well. Hoping to get some input on C2 fuel pump bolts.

Below is what I have been able to consolidate from the forum, aim, and P&A's, with Part#'s corresponding sizes and applications. It raises a few questions and Could use some help confirming and if I have this correct. As a side note; There seem to be inconsistencies between what has been reported on the forum and what the P&A catalogs list, specifically length. Also with what finishes versus what's stated in the JM's. Hoping I could get some clarity. Thanks in advance.

Small blocks

58-E67 #37518421-1/41-1/8)
Configuration believed to be; Indented Flanged(Washer head) w/ split l. washer.
Question; Whats the typical length 1-1/4 or 1-1/8 and Finish Cad or phos?

67-E72 #37785261-1/2 (part # NOT listed in P&A's)
(Configuration believed to be; Indented NON Flanged w/ split l. washer.
Question; Whats the correct length and Finish Cad or phos?

*NOTE there is a (Revision recorded in 66 AIM replacing #3751842 with #3778526).
BUT #3751842 continues in all P&A's and does NOT appear to have been discontinued. Does this imply it was the service bolt for 67-E72 #3778526 and 8526 was Never available in service? 1-1/8)
Configuration believed to be; Indented Flanged(Washer head) w/ split l. washer. Believed to be phos.

Another question;
In the P&A's small block fuel pump bolts #3751842 and big block fuel pump bolts #3874876 are both1-1/8

I was always under the impression that the Small block bolts are longer than the Big block bolts. Could someone help clarify?


Thanks again and hoping to solve

[Ronald L.]

Re: Need help with C2 fuel pump bolt identification

Rick,
The head marks of the earlier year fuel pump bolts are probably different than what was available in the 70's from GMPD, and definitely different than the repro, and those bolts Sourced to St Louis are going to be different than those sourced to one of the other GM assembly plants!

I'm pretty sure tho... the long ones are big block,
3874876 is the part number cc pr reference so that will be the long one

and short ones - two lengths they are >>> small block,
see pic,

parts in the small bags at upper left are REPROIMG_2746[1].jpg,

Small Block Short - repro zinc,
BB long repro - phos.

Loose bolts REAL originals.

[Rick B.]

Re: Need help with C2 fuel pump bolt identification

Ron, thanks for the response. Anyway for you to provide specific measurements of your Long vs shorts? The Cads vs Phos? By doing so we could align to part#'s in aim and measurements listed from the P&A's.

Certainly the repro houses are going to have there own specific measurements that I would think can be indicated not just by Headmark but by what length they chose to go to market with. As for example Paragon looks to be using 1" RSC's both in Cad and Phos. Which interestingly enough doesn't align to any of the part#s and specs in my post above. So we can rule those out quickly.

[David B.]

Re: Need help with C2 fuel pump bolt identification

P & A part #3751842 - 3/8 - 16 x 1 1/8 is correct

[Ronald L.]

Re: Need help with C2 fuel pump bolt identification

Rick, fyi...No one uses CAD - unless it was brake or safety related back then it was expensive and toxic.

On the repros PR did most of this regardless of the source, they all share parts and TPE has them, but not CC or PR in stock, go figure.

Remember - back in 1980 +/- 5 years the place GM stored nearly all Corvette service parts was Flint. PR was just a few miles away as they got started so what GM had for Service head marks was their starting point, not correct for Mid-years.

Sizing: there are three sizes I ma seeing of originals:

see pic, the big block are the long ones and a "flying F" was the early one, late motors and not Corvette Plant could be the other zinc plated versions I see.

The measurments are the lengths under the flange head - they will not take into account a lock washer as doing so introduces measurement errors.
IMG_2748.jpg

[Rick B.]

Re: Need help with C2 fuel pump bolt identification

Ron, thanks for the reply: Only more confusion and discrepancy.

Think people always been under the impression and the consensus has been Long Zinc =SB (due to the adapter plate) and BB phos short. Is this not what you're seeing?

David, if 3751842 is the 1-1/8 length (which corresponds to SB in the P&A books, then that would be the 3rd bolt in Rons pic. Interesting that bolt appears black phos? BTW The P&A's spec 1-1/8 length for BOTH SB #3751842 and BB #3874876, Ron's 1.13.

SO questions remain. Whats the typical length and finish of the SB and BB fuel pump bolts and what is the corresponding AIM part numbers?

Any help here much appreciated