1967 Bolt head ID and application

[Richard M.]

Re: 1967 Bolt head ID and application

I agree that any of those "triangle" bolts should be replaced with graded bolts. Since 3847758 original bolts have 3 lines, they are likely Grade 5 (GM 280-M). So those hood hinge bolts should be replaced to match original design specs as well as any others found on the car.

Curiously, I've been searching for that 3847758 SCREW ASM in all of the GM parts books I have access to (online). It does not show up in any Corvette P&A catalogs as listed for 1963 to 1967 Corvette, or as well as any other GM car or truck.

Is it possible that the 3847758 was never available in service?

I did find a Supersession listing dated Sept 1979, that replaces the 3847758 part with:

180078 Screw (5/16"-18, 7/8" Long)
138485 Washer (External Tooth 5/16")

Rich

[Garry B.]

Re: 1967 Bolt head ID and application

I have no idea Rich.

[Joe L.]

Re: 1967 Bolt head ID and application

I agree that any of those "triangle" bolts should be replaced with graded bolts. Since 3847758 original bolts have 3 lines, they are likely Grade 5 (GM 280-M). So those hood hinge bolts should be replaced to match original design specs as well as any others found on the car.

Curiously, I've been searching for that 3847758 SCREW ASM in all of the GM parts books I have access to (online). It does not show up in any Corvette P&A catalogs as listed for 1963 to 1967 Corvette, or as well as any other GM car or truck.

Is it possible that the 3847758 was never available in service?

I did find a Supersession listing dated Sept 1979, that replaces the 3847758 part with:

180078 Screw (5/16"-18, 7/8" Long)
138485 Washer (External Tooth 5/16")

Rich

Richard------


It's a small point but the 3847758 was actually a GM 275-M spec bolt. Note that it has 3 radial but the lines are not spaced 120 degrees apart. They are spaced 90 degrees apart. This designates a GM 275-M fastener.

I cannot find that the GM #3847758 was ever available from GM in SERVICE. However, I do find a GM reference that specifies to use the bolt and washer you mention to replace the 3847758. While 3847758 is a Chevrolet part number, it is possible that this fastener was once available in SERVICE but only from non-automotive GM parts channels (e.g. Frigidaire, EMD, etc.).

[Richard M.]

Re: 1967 Bolt head ID and application

Richard------


It's a small point but the 3847758 was actually a GM 275-M spec bolt. Note that it has 3 radial but the lines are not spaced 120 degrees apart. They are spaced 90 degrees apart. This designates a GM 275-M fastener.

I cannot find that the GM #3847758 was ever available from GM in SERVICE. However, I do find a GM reference that specifies to use the bolt and washer you mention to replace the 3847758. While 3847758 is a Chevrolet part number, it is possible that this fastener was once available in SERVICE but only from non-automotive GM parts channels (e.g. Frigidaire, EMD, etc.).

Thanks Joe,

I missed the GM-275-M reference. I didn't realize the orientation of the 3 lines made a difference. Good to know. And thanks for clarifying it's non-availability for service.

FYI I did see the 3847758 usage in several other online AIMs for the 1979 Corvette, 1964 Corvair, 1969 Camaro and 1982 Trucks.

One last thing.... I couldn't find any Grade classification for the replacement bolt, 180078. In most Standard Hardware listings I see, it usually references bolts as being GM-280-M, unless specified otherwise. The page I link referenced has no such statement.

Do you have any Grade data for the 180078?

Rich

[Joe L.]

Re: 1967 Bolt head ID and application

Thanks Joe,

I missed the GM-275-M reference. I didn't realize the orientation of the 3 lines made a difference. Good to know. And thanks for clarifying it's non-availability for service.

FYI I did see the 3847758 usage in several other online AIMs for the 1979 Corvette, 1964 Corvair, 1969 Camaro and 1982 Trucks.

One last thing.... I couldn't find any Grade classification for the replacement bolt, 180078. In most Standard Hardware listings I see, it usually references bolts as being GM-280-M, unless specified otherwise. The page I link referenced has no such statement.

Do you have any Grade data for the 180078?

Rich

Rich-----


GM #180078 = GM 280-M

[Gary B.]

Re: 1967 Bolt head ID and application



David, The part# is 3847758 SCREW ASM (AIM UPC 11-13 Sheet B6)

They're similar to what was used to attach the seat tracks to the floor, 3847757(AIM UPC 1 Seats Sheet J5), also SCREW ASM, likely a different length. IIRC both are 5/16" Course thread.




Garry, Those hinge attach bolts you show are not the typical integrated bolt and washer like in Leif's and Owen's photos. Not saying they're not original, just not typical.

I did some searching and the Triangle symbol is the manufacturers mark, Infasco in Canada.

See page 12 of the pdf below(can't upload....too big)

https://www.electronicfasteners.com/wp-content/uploads/2014/09/northamericanmfgidentificationmarkings.pdf

Rich

Rich,

Could that bolt headmark PDF document from electronicfasteners.com be included among the restoration documents accessed thru the stickies? Or maybe it’s already there and I can’t find it.

Gary

[Richard M.]

Gary, Unfortunately, the filesize exceeds our 2.86 MB upload limit. It's 4.58Mb.

Rich

[Gary B.]

Rich,

Could the file be split in two, say A-L and M-Z. Or whatever gets each half to be under 2.88 MB?

Gary

[Richard M.]

That's a good idea but I'm not a Acrobat licensed user. Maybe a volunteer could help.

I sent a note to a pdf expert.

Rich

[Richard M.]

It appears our upload limit is increased. However, it may be a bug. This now works. It's 4.58Mb. The limit used to be 2.86Mb.

I'll have to check in with the Administrators. It may be a oversight(bug).

northamericanmfgidentificationmarkings (1).pdf

[Gary B.]

Rich,

The 2.86 Mb limit seems really outdated. Almost every digital photo someone sends to me these days is double that size.

Gary

[Richard M.]

Rich,

The 2.86 Mb limit seems really outdated. Almost every digital photo someone sends to me these days is double that size.

Gary

Gary, I agree, but it's a issue of server space that we have to pay for.... which is a lot.

Rich

[Gary B.]

Ah, I understand. Sort of like cable TV or streaming services. You pay forever and the price never goes down.

Gary

[Owen L.]

I have full-on Acrobat and saved the file as "Optimized" which output a 2.4MB file - (didn't see any quality difference compared to the 4.8MB file). Might help anyone without the download speed or storage space.

[Richard M.]

Owen, Thanks. I also got a opt version yesterday and will put that in the Sticky later.

Rich