63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

**Joe L.** · September 5, 2020, 02:34 PM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Dave-------

There are VERY few 1/2" bolts used on Corvettes. As far as C2 and C3 are concerned, the only ones I can think of are the manual transmission-to-bellhousing, harmonic balancer center bolt, and a few C3 bumper-related bolts. The ones you picture are obviously not the transmission or balancer bolts. The C3 bumper bolts I am aware of are 1-1/2" and all thread. So, it's possible that's where these bolts originated. Of course, it's also possible they are off some non-Corvette passenger car.

**David L.** · September 6, 2020, 11:11 AM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Joe,
My 1970 Corvette AIM (UPC 14, Sheet A2) lists 2 different 1/2"-13 bolts, 9419101 and 3926435. After researching on the web GM # 9419101 is 1/2"-13 X 1 3/4" and GM # 3926435 is 1/2"-13 X 1". You are probably right about the 1/2"-13 X 1 3/8" bolts having a non-Corvette application. I have no idea where I got them. I should have bagged and tagged them years ago which is my normal MO.
Dave

**Mike B.** · September 7, 2020, 08:47 AM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Hi Dave,

Sorry, I can't help you place your two 1/2"-13 X 1 3/8" bolts. They're beauties. You and Joe have mentioned the transmission to bellhousing and harmonic balancer bolts but there's another 1/2" inch bolt that I know of for '66-'74 air conditioned 427/454 Corvettes. Its the compressor pivot adjustment bolt that passes through the slotted stamped steel flat bracket then bolts into the front cast iron bracket mounted to the right head's front face. This single bolt is rather hard to find. Lots of repros out there but originals are a trick.

I've flagged this 1/2"-13 X 1 1/2" grade 5 zinc bolt on this old '66 AIM page. It's part number is #180177. Check these dimensions in GM Engineering Standards sheet B-1.128. I'm including a closeup shot that my buddy Ric up in Canada sent me of his '66 AC L36 convertible's original bolt. My original was tossed by Bubbuh long ago. Thanks to Ric I know of a period correct head mark to hunt for. Mike

AIM UPC C60 Sheet C3 Bolt #180177.jpg Ric's #3887166 Adjusting Bolt & Washer (5).jpg

**David L.** · September 7, 2020, 02:14 PM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Mike,
I have found the following on the web:
180173, 1/2"-13 X 1"
180175, 1/2"-13 X 1 1/4"
180177, 1/2"-13 X 1 1/2"
My 1963 and 1966 Chevrolet Parts Catalogs (Oct. 1962 and Oct. 1965) list only the following 1/2"-13 bolts with part numbers starting with "180" in Gr. 8.900:
180172, 1/2"-13 X 7/8"
180183, 1/2"-13 X 2 1/4"
180190, 1/2"-13 X 3"
180191, 1/2"-13 X 3 3/4" (1 1/4" thd. length)((280-M)
My friend LOGIC tells me that my 1/2"-13 X 1 3/8" bolt with "WB" on the head could be GM # 180176. It was probably a production line bolt and never sold over the counter as a 1/2"-13 X 1 1/2" bolt could be used as a replacement.
I could not find anything on the web about GM bolt # 180176.
Thanks for your comments. They were quite helpful, hopefully steering me down the right path.
Dave

**Domenic T.** · September 7, 2020, 02:21 PM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Dave,
what about trans to bell housing, otherwise I would guess bumper.

Dom

**David L.** · September 7, 2020, 02:24 PM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Dom,
I have four original 1/2"-13 X 1 3/4" bolts with "TR" on the bolt head that are manual transmission to bell housing bolts.
Dave

**Joe L.** · September 7, 2020, 04:16 PM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Originally posted by David Liukkonen (3775)

While looking for various parts in my collection I came across two ORIGINAL 1/2"-13 X 1 3/8" bolts with full length threads, "WB" markings, and heavy duty 1/2" lock washers. At first I thought that they were M.T. to bellhousing bolts but after studying them further I realized that the M.T. to bellhousing bolts are 1 3/4" in length. The Standard Parts section in my 1966 and 1969 Chevrolet parts catalogs list a 1/2"-13 X 1 3/8" bolt as GM # 3852924 in Gr. 8.900 and Gr. 4.105. My May 1966 Chevrolet Truck parts catalog lists GM # 3852924 in Gr. 4.105 as a clutch housing bolt (5 required) for 63-65 Ser. 60 trucks. I have never worked on one of these trucks.
I would appreciate any comments.
Dave

Dave------

Are these bolts zinc plated? I can't really tell if they are zinc plated or natural steel well cleaned with a wire wheel. Bolts of GM #180xxx were zinc plated.

GM #180176 was once available in SERVICE. It was discontinued in July, 1974. I don't have specs on it but I also think it's almost certainly a 1/2-13 X 1-3/8" bolt, zinc plated, and of GM 280-M material grade. There was at least one other bolt of those dimensions available in SERVICE. It was GM #9425710. However, it was phosphate finished and of GM 300-M material grade.

**Joe L.** · September 7, 2020, 04:23 PM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Originally posted by Mike Browning (24893)

Hi Dave,

Sorry, I can't help you place your two 1/2"-13 X 1 3/8" bolts. They're beauties. You and Joe have mentioned the transmission to bellhousing and harmonic balancer bolts but there's another 1/2" inch bolt that I know of for '66-'74 air conditioned 427/454 Corvettes. Its the compressor pivot adjustment bolt that passes through the slotted stamped steel flat bracket then bolts into the front cast iron bracket mounted to the right head's front face. This single bolt is rather hard to find. Lots of repros out there but originals are a trick.

I've flagged this 1/2"-13 X 1 1/2" grade 5 zinc bolt on this old '66 AIM page. It's part number is #180177. Check these dimensions in GM Engineering Standards sheet B-1.128. I'm including a closeup shot that my buddy Ric up in Canada sent me of his '66 AC L36 convertible's original bolt. My original was tossed by Bubbuh long ago. Thanks to Ric I know of a period correct head mark to hunt for. Mike

[ATTACH=CONFIG]100977[/ATTACH][ATTACH=CONFIG]100978[/ATTACH]

Mike------

I really don't see what's so unique about this bolt aside from, perhaps, the manufacturer's headmarking which could have varied anyway. Otherwise, a bolt of this configuration and finish could be obtained in most good hardware stores.

It's also possible that the bolt you picture has a chromate (gold) overplate. If so, it's likely not an original bolt. While common now, chromate overplate was rarely used on original fasteners of the period.

**Mike B.** · September 7, 2020, 05:30 PM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Hi Dave,

Since the part number for the '66 transmission to bellhousing bolt hasn't been mentioned yet I figured I'd include it now. It's part number is 100161. It's shown in this old '66 AIM base transmission page. Nothing listed under M20/21 pages. It's dimensions are 1/2"-13 X 1 3/4 Grade 2 plain steel. Check out GM Engineering Standards page B-1.122. I'm assuming this part number was used throughout '63-'67?

The four small font "TR" bolts that you've shown are excellent original examples. I've got some of those in my 100161 collection. I've also rounded up some real nice "WB" and "A" headmarked versions. I've snipped your bolt image headmarks and show them here again as examples of bolt 100161. Your mystery "WB" bolts have the exact same "dished" head style that my 100161 "WB" versions have. Sorry, no shots of the "A" headmark version with me.

Nice "TR" bolts Dave.
Mike

'66 AIM Transmission to Bellhousing Bolts.jpg David's TR Transmission Mount Bolt.JPG David's WB Mystery Bolt.jpg

**David L.** · September 7, 2020, 07:53 PM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Originally posted by Joe Lucia (12484)

Dave------

Are these bolts zinc plated? I can't really tell if they are zinc plated or natural steel well cleaned with a wire wheel. Bolts of GM #180xxx were zinc plated.

GM #180176 was once available in SERVICE. It was discontinued in July, 1974. I don't have specs on it but I also think it's almost certainly a 1/2-13 X 1-3/8" bolt, zinc plated, and of GM 280-M material grade. There was at least one other bolt of those dimensions available in SERVICE. It was GM #9425710. However, it was phosphate finished and of GM 300-M material grade.

Joe,
Since the bolts had surface rust on them I cleaned then off with my wire wheel. At present there does not seem to be any plating left on them.
My GM Parts History shows that GM # 180176 was discontinued in Dec. 1974 in the Group No. "OPEL".

BTW, I once owned a yellow 1970 Opel GT back in 1978-1979........."A Poor Man's Corvette". I sold it in 1979 to a someone in Manchester, NH. A few years later I saw the exact same car in a salvage yard in Greenfield, MA with a large "V" dent in the front bumper (telephone pole collision, I assume). I bought my 1966 Corvette convertible in 1979.

On the web I also found that GM # 180176 was replaced by GM # 9419099 (1/2"-13 X 1 1/4" full thread) which was replaced by GM # 9425082 (1/2"-13 X 1 1/4", 300M).
Dave

**Joe L.** · September 7, 2020, 10:20 PM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Originally posted by David Liukkonen (3775)

Joe,
Since the bolts had surface rust on them I cleaned then off with my wire wheel. At present there does not seem to be any plating left on them.
My GM Parts History shows that GM # 180176 was discontinued in Dec. 1974 in the Group No. "OPEL".

BTW, I once owned a yellow 1970 Opel GT back in 1978-1979........."A Poor Man's Corvette". I sold it in 1979 to a someone in Manchester, NH. A few years later I saw the exact same car in a salvage yard in Greenfield, MA with a large "V" dent in the front bumper (telephone pole collision, I assume). I bought my 1966 Corvette convertible in 1979.

On the web I also found that GM # 180176 was replaced by GM # 9419099 (1/2"-13 X 1 1/4" full thread) which was replaced by GM # 9425082 (1/2"-13 X 1 1/4", 300M).
Dave

Dave------

Yes, I also found the Opel reference for the 180176. However, I think the Opel Division had a part numbering system different than the regular GM system. Thus, there were two 180176's. In the Opel system, the 180176 was not a bolt.

I could not find a direct line of supersession between the 180176 and the 9419099. However, the 9419099 was superseded by the 9425082 in December, 1976. Both were 1/2-13 X 1-1/4". So, I would more expect that these superseded the 180175 which had the same dimensions although I cannot confirm that supersession. The 9425710 was a 1/2-13 X 1-3/8".

**David L.** · September 8, 2020, 08:38 AM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Originally posted by Joe Lucia (12484)

Dave------

Yes, I also found the Opel reference for the 180176. However, I think the Opel Division had a part numbering system different than the regular GM system. Thus, there were two 180176's. In the Opel system, the 180176 was not a bolt.

I could not find a direct line of supersession between the 180176 and the 9419099. However, the 9419099 was superseded by the 9425082 in December, 1976. Both were 1/2-13 X 1-1/4". So, I would more expect that these superseded the 180175 which had the same dimensions although I cannot confirm that supersession. The 9425710 was a 1/2-13 X 1-3/8".

Joe,
From my GM Part Number Replacements and Supersessions Manual (Jan. 1967 to Oct. 1980).
Old No. 180176........Use 9419099
Dave

**Mike B.** · October 7, 2020, 04:55 AM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Dave,

Have you seen this current thread about transmission to bellhousing bolts that's currently on the TDB? I just realized that we now have the answer to your bolt info request from last month. Your 1/2"-13 X 1 3/8" WB bolts were used on '64-'65 lower transmission to bellhousing bolts. Lower left or both lowers? Just confirmed the specs of GM bolt #106342 in the GM Engineering Standards page B-1.122.

You've probably solved this already but if not, here ya go. Mike

Grant MacDonald Bolt Thread.jpg

**David L.** · October 7, 2020, 09:04 AM

Re: 63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

Originally posted by Mike Browning (24893)

Dave,

Have you seen this current thread about transmission to bellhousing bolts that's currently on the TDB? I just realized that we now have the answer to your bolt info request from last month. Your 1/2"-13 X 1 3/8" WB bolts were used on '64-'65 lower transmission to bellhousing bolts. Lower left or both lowers? Just confirmed the specs of GM bolt #106342 in the GM Engineering Standards page B-1.122.

You've probably solved this already but if not, here ya go. Mike

[ATTACH=CONFIG]101592[/ATTACH]

Mike,
I had not solved this issue. I thought that the 2 bolts might be transmission to bell housing bolts but the length did not make sense to me because they were 3/8" shorter than my other transmission to bellhousing bolts. I do have a set of for 1/2"-13 X 1 3/4" bolts with "TR" markings as well as a set of four 1/2"-13 X 1 3/4" bolts with "WB" markings.
The 106342 bolts are also listed in my 1963 Corvette Assembly Manual (Sect. 7, Sheet B2.00).
Thanks for not giving up and solving this issue.
Dave

63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

63-67 Corvette 1/2"-13 X 1 3/8" WB Bolt Question

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