Fan clutch attachment to water pump

[G A.]

The judging manual says cars built after the spring of 1969 used studs, split washers and nuts to attach the clutch to the pump, not bolts. Any of you have an example of this ?? The car I'm working on now was built 10/69.

Dan

[Rich P.]

Re: Fan clutch attachment to water pump

Several years ago I restored a 10-69 built 435 and it had Grade 8 AS headmarking bolts. It was a very original untouched car. I'd like to se some survivors with studs.

Rich

[Joe L.]

Re: Fan clutch attachment to water pump

The judging manual says cars built after the spring of 1969 used studs, split washers and nuts to attach the clutch to the pump, not bolts. Any of you have an example of this ?? The car I'm working on now was built 10/69.

Dan

Dan------


My original owner 1969 small block which was built in mid September, 1969 had studs and nuts.

The AIM also specifies studs and nuts. However, the page was "redrawn and redesigned" as of mid-March, 1969. I expect that 1st design 1969 used bolts. However, I would expect that by June, or so, the studs would have made their way to the assembly line.

I am surprised to hear Rich's report that an October, 1969 car had bolts.

[G A.]

Re: Fan clutch attachment to water pump

This is the most frustrating part of this endeavor.
There exists a book. The book says X=Y. There are GENERALLY examples that SOMETIMES say X DOES NOT equal Y. Certainly I understand that if a judgement is to be made, a benchmark must be set. If one publishes a book why can't the book give a reasonable, documented variance, rather than say "ONLY THIS"???

Another example is on the alternator fan for an L-71. The '68-'69 book says one groove per blade, but you educated, studied gentlemen that I tend to trust say otherwise, and I tend to lean towards the blades NOT being 'one groove per blade'.
As Charlie Brown used to say "AUGH"!!!

PS. Thanks Joe and Rich

Dan

[Terry M.]

Re: Fan clutch attachment to water pump

The judging manual says cars built after the spring of 1969 used studs, split washers and nuts to attach the clutch to the pump, not bolts. Any of you have an example of this ?? The car I'm working on now was built 10/69.

Dan

I don't suppose it matters to your survey Dan, but my 1970 (January 29 on the trim tag) small block has studs, split lock washers and nuts. It also has a dual pattern hub on the never removed from the engine water pump.

[Dick W.]

Re: Fan clutch attachment to water pump

Several years ago I restored a 10-69 built 435 and it had Grade 8 AS headmarking bolts. It was a very original untouched car. I'd like to se some survivors with studs.

Rich

I am not sure that I have seen grade 8 bolts in this application. Grade 5 may, but 8?

[Joe L.]

Re: Fan clutch attachment to water pump

I am not sure that I have seen grade 8 bolts in this application. Grade 5 may, but 8?

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".

[G A.]

Re: Fan clutch attachment to water pump

Could someone give me the finish details on the studs, nuts, and washers?

Dan

[Joe L.]

Re: Fan clutch attachment to water pump

Could someone give me the finish details on the studs, nuts, and washers?

Dan

Dan-----


The studs were definitely black phosphate. I just do not recollect on the nuts and washers. Vaguely, I recall that they MIGHT have been black phosphate, too.

[Terry M.]

Re: Fan clutch attachment to water pump

Could someone give me the finish details on the studs, nuts, and washers?

Dan

It may not matter but on my 1970 they are all silver color, I would assUme zinc -- studs, nuts & washers.

[Joe L.]

Re: Fan clutch attachment to water pump

It may not matter but on my 1970 they are all silver color, I would assUme zinc -- studs, nuts & washers.

Terry-----


Well, 1970 was supposed to use the same studs, nuts and washers as 1969. As I mentioned, I'm not sure about the nuts and washers but I'm certain of the studs. They were GM #3964274 and my originals were definitely black phosphate. I also have several NOS examples of these studs and they're black phosphate, too.

One other thing: these studs, nuts, and washers were GM 300M material (SAE grade 8). During the 60's and 70's most of the 300M fasteners that GM used in PRODUCTION were either black phosphate or "plain" finish.

[Terry M.]

Re: Fan clutch attachment to water pump

Terry-----


Well, 1970 was supposed to use the same studs, nuts and washers as 1969. As I mentioned, I'm not sure about the nuts and washers but I'm certain of the studs. They were GM #3964274 and my originals were definitely black phosphate. I also have several NOS examples of these studs and they're black phosphate, too.

One other thing: these studs, nuts, and washers were GM 300M material (SAE grade 8). During the 60's and 70's most of the 300M fasteners that GM used in PRODUCTION were either black phosphate or "plain" finish.

I agree grade 8 fasteners are usually dark colored due to the heat treatment involved to get them to that strength.

I might have to go look at these things. I remember the studs being a little "strange" in that the threads for the nut are NC, but the threads into the hub are NF.

[Joe L.]

Re: Fan clutch attachment to water pump

I agree grade 8 fasteners are usually dark colored due to the heat treatment involved to get them to that strength.

I might have to go look at these things. I remember the studs being a little "strange" in that the threads for the nut are NC, but the threads into the hub are NF.

Terry------


Yes, these studs were 5/16-18 on the outer end and 5/16-24 on the inner end. They were necessarily 5/16-24 on the inner end because that's what the waterpump hubs were tapped for. However, why they didn't use the same thread on the outer is beyond me.

[Lawrence M.]

Re: Fan clutch attachment to water pump

It may not matter but on my 1970 they are all silver color, I would assUme zinc -- studs, nuts & washers.

These studs, nuts and washers are on a Dec 15th built 1969 L-46. The car has been restored in the past, so I do not know if the nuts and washers are original. I doubt they are. However the last time I had the fan off the patina on the studs looked like they could be original.

Larry

[Terry M.]

Re: Fan clutch attachment to water pump

The judging manual says cars built after the spring of 1969 used studs, split washers and nuts to attach the clutch to the pump, not bolts. Any of you have an example of this ?? The car I'm working on now was built 10/69.

Dan

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.