70 alarm horn bolt

[Bill L.]

What bolt is used to attach the alarm horn. AIM calls out #180075. A search tells be it is a 5/16-18 x 5/8" bolt but what head type? Indented hex, standard hex? What was the finish of the bolt?

As a side note the date stamped on the horn happens to be stamped directly on top of the 938 pn.

Bill

[Joe L.]

Re: 70 alarm horn bolt

What bolt is used to attach the alarm horn. AIM calls out #180075. A search tells be it is a 5/16-18 x 5/8" bolt but what head type? Indented hex, standard hex? What was the finish of the bolt?

As a side note the date stamped on the horn happens to be stamped directly on top of the 938 pn.

Bill

Bill------


The information I have says it was a GM 280-M grade bolt (i.e. SAE grade 5; 3 radial lines), zinc plated, and trimmed head (i.e. "non-indented" head). As far as manufacturer's ID headmarkings, I have no information.

[Bill L.]

Re: 70 alarm horn bolt

Bill------


The information I have says it was a GM 280-M grade bolt (i.e. SAE grade 5; 3 radial lines), zinc plated, and trimmed head (i.e. "non-indented" head). As far as manufacturer's ID headmarkings, I have no information.

Thanks Joe,

I think I have the right bolt. RSC head mark, 3 radial lines and zinc plated with trimmed head.

Your parts knowledge is nothing short of astounding. Do you have GM illustrated parts manuals?

Bill

[Alan S.]

Re: 70 alarm horn bolt

Hi Bill,
A bolt with that part number is used on 71 cars for the end of the engine grounding cable that is attached to the frame engine mount.
On my car that bolt is as Joe described and has an 'A' head mark and 3 radial lines.
I'd think that there were probably other suppliers and head marks.
Regards,
Alan

[Bill L.]

Re: 70 alarm horn bolt

Hi Bill,
A bolt with that part number is used on 71 cars for the end of the engine grounding cable that is attached to the frame engine mount.
On my car that bolt is as Joe described and has an 'A' head mark and 3 radial lines.
I'd think that there were probably other suppliers and head marks.
Regards,
Alan

70 AIM is the same and the bolt is an A head mark on mine exactly as described Alan. In fact the bolt holding the starter brace and other end of that same ground wire is the same. These bolts match the configuration of the RSC bolt I have in every way other than the head mark. I do have other RSC head mark bolts elsewhere on the car so I am good to go.

Your knowledge is priceless!

Bill

[Joe L.]

Re: 70 alarm horn bolt

Thanks Joe,

. Do you have GM illustrated parts manuals?

Bill

Bill-------


Yes, I have many among other references.

[Bill L.]

Re: 70 alarm horn bolt

Still unresolved. Attached is a pic from a known original horn bolt from a 70 (juliet's) which jibes with another member who has a 70 LT1 they are restoring.

This bolt does not jibe with what is called out in the AIM. Even the head mark is the same on both 70s.

The AIM also calls out a lock washer for under the bolt instead of an external toothed washer.

Love for some additional 70 owners to chime in with thoughts and or pics.

The pic below is from Juliets 70 I obtained from her restoration page.

Bill UA6 Mount.jpeg

[Joe L.]

Re: 70 alarm horn bolt

Still unresolved. Attached is a pic from a known original horn bolt from a 70 (juliet's) which jibes with another member who has a 70 LT1 they are restoring.

This bolt does not jibe with what is called out in the AIM. Even the head mark is the same on both 70s.

The AIM also calls out a lock washer for under the bolt instead of an external toothed washer.

Love for some additional 70 owners to chime in with thoughts and or pics.

The pic below is from Juliets 70 I obtained from her restoration page.

Bill [ATTACH=CONFIG]51451[/ATTACH]

Bill------


I cannot see the bolt in the photo. The photo is too small.

It is possible that for a part like this bolt, the factory substituted some part number other than the one shown in the AIM.

Also, the term "L. Washer" (for lockwasher) does not necessarily mean a split lock washer. As a matter of fact, the GM #138485 specified for this application is a 5/16", zinc plated external tooth lockwasher.