Fan clutch attachment to water pump

[Ronald L.]

Re: Fan clutch attachment to water pump

Terry,
There are some here that have the Gm engineering standard book, that would tell us the grade. You are right, you don't put a G3 lock washer on a bolt-nut combo in the G8 range, the lock washer would fail.

[Joe L.]

Re: Fan clutch attachment to water pump

Larry Ms post should work for you, Dan.

I am still trying to deal with the grade 8 specification. I know grade 8 nuts when I see them and these ain't them, and I am real puzzled about the grade 8 stud. If you had a coffee can full of these and some others how would you tell the grade 8 studs or nuts from the grade anything else? The grade 8 nuts I have seen have little dots on the top part of them -- the side that does not go against the lock washer has 6 dots for grade 8. I know there are grade 8 flat washers (the plating tells the grade), but I am not sure about split lock washers though. The whole fastener system has to work as a unit, otherwise it is only as strong as its weakest part.

Terry-----


These could very well be the original nuts and lockwashers. My memory is really foggy on the finish of the nuts and washers. They could very well have been zinc plated.

There's no way I know of to tell a grade 8 stud from any other grade by looking at it. The only way I know of is to know the GM part number and the specs for that part number. The only way to know the part number is to have them in a GM package with that part number on it.

In the aftermarket, Dorman identifies its studs by material grade. So, if you get a Dorman stud of a particular part number, you'll know what grade it is.

The marking you describe for grade 8 nuts has been in use for the past 25 years, or so. However, prior to that time, nut were not usually identified as to grade.

There is such a thing as grade 8 lockwashers. My fastener bins are full of such lockwashers in every common size. There are also grade 8 FLAT washers. I'm fully stocked on those, too.

[Terry M.]

Re: Fan clutch attachment to water pump

Terry-----


These could very well be the original nuts and lockwashers. My memory is really foggy on the finish of the nuts and washers. They could very well have been zinc plated.

[Domenic T.]

Re: Fan clutch attachment to water pump

Dick-----


The GM #186634 bolts used for fan clutch-to-water pump attachment for 1968 (and, most likely, also used for early 1969) were GM 300M material spec (SAE grade 8). They were 5/16-24 X 1".

Joe,

Was that also true for 1967?

DOM

[Joe L.]

Re: Fan clutch attachment to water pump

Joe,

Was that also true for 1967?

DOM

Dom-----


Same bolts for 1967.

[Domenic T.]

Re: Fan clutch attachment to water pump

Dom-----


Same bolts for 1967.

Joe,

Thanks.

DOM