C3 Exhaust Pipe Clamps: 1978-79

[Tom R.]

Bowtie judging presents optimum opportunities to see and learn OEM configurations...especially chassis given use of lifts. After much study of low-mileage Bowtie candidates I've seen two clamp types used to secure pipe intersections for both L48 and L82 applications. L82s used a 2 1/2" rear Y-pipe while L48s called out a 2" rear Y-pipe; all other exhaust system parts were nearly the same...catalytic converter and mufflers...well, the rear muffler pipes were configured to fit the rear Y-pipe size.

The forward applications for both L48 and L82, from the catalytic converter to the header pipes use a pipe extension and a flattened U-bolt open-style clamp with flange nuts. A K was debossed at the arch of the flattened U-bolt (see photo). These same clamps were used with the 2 1/2" L82 rear Y-pipe to muffler connection while L48 rear Y-pipes used a round 2" U-bolt clamp. The 2" U-bolt clamp, also an open-style (see photo), was used for either an L48 or L82 to secure the muffler tip to the muffler hanger. It appears that the 2" clamp also used flange nuts. (see photo)

My questions are

1. Apparently early C3s also used a flattened U-bolt with the K mark but were of a guillotine style. What's the K represent?
2. Are both these nut P/Ns flange nuts (from the 78 AIM)? 1361640 and 1359887
3. I take it the 2" U-bolt is a common part and the P/N tells me its been around awhile. Did the 2 1/2" U-bolt find early use? 412292 (2") vs. 3949198 (2 1/2")

I did do a search and found several threads discussing C2 and early C3 exhaust pipe clamps. This discussion will hopefully add to the C3 exhaust pipe clamp discussion.

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[David B.]

Re: C3 Exhaust Pipe Clamps: 1978-79

Tom, Not sure you if you are aware: 412292 is an Oldsmobile designed part number. 1361640 & 1359887 are original Buick design parts and 3949198 is Chevrolet design listed in Grp.3.708.

[Terry M.]

Re: C3 Exhaust Pipe Clamps: 1978-79

Tom
I believed (just a SWAG) that the "K" referrs to the clamp manufacturer.

[Tom R.]

Re: C3 Exhaust Pipe Clamps: 1978-79

Tom, Not sure you if you are aware: 412292 is an Oldsmobile designed part number. 1361640 & 1359887 are original Buick design parts and 3949198 is Chevrolet design listed in Grp.3.708.

All of which are called out in the 1978 AIM...I'm sure by the mid-1970s, the assembly divisions were not beyond sharing parts. In fact, General Motors had completed its takeover and management of the plants and, more than likely, demanded it.

[Tom R.]

Re: C3 Exhaust Pipe Clamps: 1978-79

Tom
I believed (just a SWAG) that the "K" refers to the clamp manufacturer.

And represents...?

[David B.]

Re: C3 Exhaust Pipe Clamps: 1978-79

All of which are called out in the 1978 AIM...I'm sure by the mid-1970s, the assembly divisions were not beyond sharing parts. In fact, General Motors had completed its takeover and management of the plants and, more than likely, demanded it.

Not exactly, All GM Divisions were always encouraged to utilize Standard Engineering parts whenever possible to eliminate duplication and keep costs down. A Division was free to engineer a part and assign it's own part number if it was not available through Standard Engineering. Any Division could ask another Division for permission to use that part (it was always granted) if applicable for their use. The part number would remain as assigned by the originating Division. This info may not be relevant for your research but I found informative.

[Terry M.]

Re: C3 Exhaust Pipe Clamps: 1978-79

And represents...?

No clue Tom. I was just spitballing there

[Joe L.]

Re: C3 Exhaust Pipe Clamps: 1978-79

Bowtie judging presents optimum opportunities to see and learn OEM configurations...especially chassis given use of lifts. After much study of low-mileage Bowtie candidates I've seen two clamp types used to secure pipe intersections for both L48 and L82 applications. L82s used a 2 1/2" rear Y-pipe while L48s called out a 2" rear Y-pipe; all other exhaust system parts were nearly the same...catalytic converter and mufflers...well, the rear muffler pipes were configured to fit the rear Y-pipe size.

The forward applications for both L48 and L82, from the catalytic converter to the header pipes use a pipe extension and a flattened U-bolt open-style clamp with flange nuts. A K was debossed at the arch of the flattened U-bolt (see photo). These same clamps were used with the 2 1/2" L82 rear Y-pipe to muffler connection while L48 rear Y-pipes used a round 2" U-bolt clamp. The 2" U-bolt clamp, also an open-style (see photo), was used for either an L48 or L82 to secure the muffler tip to the muffler hanger. It appears that the 2" clamp also used flange nuts. (see photo)

My questions are

1. Apparently early C3s also used a flattened U-bolt with the K mark but were of a guillotine style. What's the K represent?
2. Are both these nut P/Ns flange nuts (from the 78 AIM)? 1361640 and 1359887
3. I take it the 2" U-bolt is a common part and the P/N tells me its been around awhile. Did the 2 1/2" U-bolt find early use? 412292 (2") vs. 3949198 (2 1/2")

I did do a search and found several threads discussing C2 and early C3 exhaust pipe clamps. This discussion will hopefully add to the C3 exhaust pipe clamp discussion.

[ATTACH=CONFIG]112408[/ATTACH]
[ATTACH=CONFIG]112407[/ATTACH]

Tom------


I really cannot add too much to this discussion. However, I'll offer this:

I can find no record of the GM #1361640 nut ever being available in SERVICE. At least, I cannot find that it was ever cataloged in SERVICE for a Chevrolet application.

The GM #1359887 nut was once available in SERVICE. It was a 5/16-18 flanged nut. It was discontinued and replaced by GM #9440046 which remains available. I have several NOS examples of the 1359887 but it's too difficult for me to access them for photos.

I can find no record of the GM #412292 u-bolt.

The GM #3949198 u-bolt was used for 2-1/2" exhaust systems beginning in 1968. It was discontinued from SERVICE without supersession in October, 1992.

Like Terry, I fully expect that the "K" embossment on the u-bolt represents a manufacturer's identification. However, I do not know what company it identifies. Most likely, a company most have never heard of. I also expect that there was more than one manufacturer that supplied this part to GM.

[Tom R.]

Re: C3 Exhaust Pipe Clamps: 1978-79

Thx Joe...this is helpful

[Tom R.]

Re: C3 Exhaust Pipe Clamps: 1978-79

Not exactly, All GM Divisions were always encouraged to utilize Standard Engineering parts whenever possible to eliminate duplication and keep costs down. A Division was free to engineer a part and assign it's own part number if it was not available through Standard Engineering. Any Division could ask another Division for permission to use that part (it was always granted) if applicable for their use. The part number would remain as assigned by the originating Division. This info may not be relevant for your research but I found informative.

David
This has the makings of a great tech article for the Restorer...despite its three-year submission to print timeframe and its just not the parts used as called out from the AIM but, as you note, the parts sharing among Divisions. This application also shows that while parts were used in 1978, the part design dates back into the 1960s. It's interesting that the 412292 U-bolt seems to lose its historical origins when viewed from the Chevrolet Cataloging process.