GM #131718 split lock washer; reg or heavy? Zinc or plain or blk phos?

[Gary B.]

According to some previous posts, GM 131718 is a split, lock washer called out in the early C2 AIMs for use with the center bolt for the harmonic balancer. Does anyone know whether that lock washer has regular dimensions, or it is a heavy or high-collar lock washer? Also, it is zinc plated, or plain, or black phosphate?


By way of related background, GM 131718 must be for a 7/16” bolt, since that is the diameter of the balancer center bolt.


I know of two versions that GM had of the regular 7/16” split lock washer. GM 103322 had a plain finish, and GM 120383 was zinc plated; the dimensions of both are: ID=0.45”, OD=0.77”, Th=0.12”.


GM 103328 is the heavy or hi-collar version of the split lock washer for 7/16” bolts. The OD and ID are the same as for the regular 7/16” lock washer, but the heavy version is 0.14” thick.


Which leaves me confused about what GM 131718 could be.


Thanks,


Gary

[Gary B.]

AACDF7CA-15CC-459F-9AAA-0BFF34DE0BA3.jpg

Which begs the question, what split lock washer is commonly seen with the harmonic balancer center bolt during the C2 era?

Gary

[Chris T.]

Re: GM #131718 split lock washer; reg or heavy? Zinc or plain or blk phos?

Gary, Rich Pasqualone has posted many pictures of balancer bolts with external tooth lock washers on CF. Chris
All Products (originalgmhardware.com)

[Gary B.]

[David B.]

Re: GM #131718 split lock washer; reg or heavy? Zinc or plain or blk phos?

131718 is a 7/16 Internal tooth lock washer (not split) .040/.032 thick cad or zinc
138484 is 1/4 External tooth lock washer zinc Check the 66 AIM again, Doubt that can be correct.

[Gary B.]

Re: GM #131718 split lock washer; reg or heavy? Zinc or plain or blk phos?

David,

Sorry, my typo on the # from the ‘66 AIM. It is 138494. My bet is that is still a toothed washer, and not a split lock washer.

Gary

[Joe L.]

Re: GM #131718 split lock washer; reg or heavy? Zinc or plain or blk phos?

David,

Sorry, my typo on the # from the ‘66 AIM. It is 138494. My bet is that is still a toothed washer, and not a split lock washer.

Gary

Gary------


External tooth lock washers were used for virtually all, if not all, harmonic balancer center bolt applications. I know of none that used a split lockwasher.

[Gary B.]

[Joe L.]

Re: GM #131718 split lock washer; reg or heavy? Zinc or plain or blk phos?

Joe,

Maybe when the pulleys or balancers are removed by owners during rebuilds, the toothed washers were sometimes replaced by split lock washer. It was your Nov 2008 posting where you talk about split lock washers, including one on your ‘69, that got me thinking that split lock washers were common. My L79 has a plain or blk phos finish, split lock washer, 0.12” thick (which is the regular thickness, not heavy), but it looks much too nice to be original.

Gary

Gary------

I don't recall the post. However, are you sure I was not referring to the balancer pulley bolts? Those do use split lock washers.

One problem with the external tooth lockwashers in the center bolt application: they are "flimsy" and can "split" due to the torque involved. Then, the torque on the bolt is released.

[Gary B.]

Another curiosity: from 1962-64 , the lockwasher specified for use with the bolt was GM #131718. This is a SPLITLOCKWASHER. From 1965-82, the lockwasher specified was GM #138494. This is an EXTERNAL TOOTH STAR WASHER. However, the AIM's through 1972 depict a splitlockwasher (although this depiction might be an anachronism). Also, my original owner 1969 small block was originally built with a splitlockwasher. Other earlier small blocks that I've observed have used splitlock washers, too, although I couldn't say that all did. But, I think that the GM #131718 was actually used in PRODUCTION for a lot longer than just through 1964.

[Joe L.]

Re: GM #131718 split lock washer; reg or heavy? Zinc or plain or blk phos?

Joe,

This was the last paragraph in your Nov 24, 2008 posting:

”Another curiosity: from 1962-64 , the lockwasher specified for use with the bolt was GM #131718. This is a SPLITLOCKWASHER. From 1965-82, the lockwasher specified was GM #138494. This is an EXTERNAL TOOTH STAR WASHER. However, the AIM's through 1972 depict a splitlockwasher (although this depiction might be an anachronism). Also, my original owner 1969 small block was originally built with a splitlockwasher. Other earlier small blocks that I've observed have used splitlock washers, too, although I couldn't say that all did. But, I think that the GM #131718 was actually used in PRODUCTION for a lot longer than just through 1964.”

Gary

Gary-------


Well, I just don't recall that but, obviously, it's what I wrote. As I sit here now, I just do not remember what type of lockwasher was originally on my 1969. Perhaps, in 2008 I had a better recollection because it was not as "distant a memory". I do know, for sure, that most of the engines I have looked at over the years had the external tooth lockwasher. This would be a very uncommon type of lockwasher for someone to use as a replacement; much more likely that if the original washer was replaced, it would be replaced with a split lockwasher.

I usually have a pretty good memory for things but, I suppose, eventually I forget something or other.

[Bill B.]

Re: GM #131718 split lock washer; reg or heavy? Zinc or plain or blk phos?

Joe,

No need to be apologetic for not remembering something from 13 yrs ago. You are a treasure-trove of detailed information that we, the NCRS Tech Discussion readers, truly appreciate and look forward to every time you post.

Thank you for your vast wealth of information which helps us in our restoration and preservation activity!

Keep up the outstanding work!

[Gary B.]

[Gary B.]

Re: GM #131718 split lock washer; reg or heavy? Zinc or plain or blk phos?