Water pump studs to fan assembly 1969

[Roger G.]

I removed the fan assembly to get the radiator and shroud out ... Which came out easily . However I had a couple of the studs back out of the water pump hub during removal of the fan and clutch. What's the best way to reseat these? Is loctite needed to keep the from backing out next time? Thanks

[Joe L.]

Re: Water pump studs to fan assembly 1969

I removed the fan assembly to get the radiator and shroud out ... Which came out easily . However I had a couple of the studs back out of the water pump hub during removal of the fan and clutch. What's the best way to reseat these? Is loctite needed to keep the from backing out next time? Thanks

roger--------


I don't really know what you mean by "re-seat". There's no need to do very much with these studs. Simply screw them into the hub. However, you do have to be sure that you have the correct studs. If the fine threaded end (i.e. that threads into the hub) is too long, it will strike the waterpump casting.

If you wish, you can use Locktite on the threads to help secure the studs and prevent their rotation in the hub but it's not necessary.


ADDENDUM:

One other thing that I recalled that may be the basis for your question. The original GM studs used for the application, GM #3964274, were a VERY poor choice for this application. This stud, which is 15/16" in total length, has a short 5/16-16 end and a long 5/16-24 end. This is just the opposite of what is needed. With this configuration, when the stud is turned down until it stops on the un-threaded shank, the fine thread end will extend too far beyond the rear of the hub and, most importantly, there will then be insufficient length on the coarse thread end to accommodate the thickness of the fan clutch hub, the lockwasher, and nut. So, one has to thread the stud into the waterpump hub only so far as it does not protrude beyond the rear of the hub. Of course, when this is done, it's difficult to maintain it in this position when the clutch is installed and the nuts are turned down. In that sense, your suggestion of using Locktite on the fine threads will be very helpful. However, I think the best plan is to obtain studs which are more suitable for the application (i.e. make a better choice of stud configuration than GM did once-upon-a-time).

A better stud will be about 1" in total length, have a fine threaded end of about 1/4", an un-threaded shank of about 1/4" and a coarse threaded end of about 1/2". The stud must be SAE grade 8. The nut and lockwasher need to be grade 8, too. And, believe me, no judge will ever know the difference (as long as you use phosphate-finished studs which most grade 8 studs will be).

[Roger G.]

Re: Water pump studs to fan assembly 1969

roger--------


I don't really know what you mean by "re-seat". There's no need to do very much with these studs. Simply screw them into the hub. However, you do have to be sure that you have the correct studs. If the fine threaded end (i.e. that threads into the hub) is too long, it will strike the waterpump casting.

If you wish, you can use Locktite on the threads to help secure the studs and prevent their rotation in the hub but it's not necessary.


ADDENDUM:

One other thing that I recalled that may be the basis for your question. The original GM studs used for the application, GM #3964274, were a VERY poor choice for this application. This stud, which is 15/16" in total length, has a short 5/16-16 end and a long 5/16-24 end. This is just the opposite of what is needed. With this configuration, when the stud is turned down until it stops on the un-threaded shank, the fine thread end will extend too far beyond the rear of the hub and, most importantly, there will then be insufficient length on the coarse thread end to accommodate the thickness of the fan clutch hub, the lockwasher, and nut. So, one has to thread the stud into the waterpump hub only so far as it does not protrude beyond the rear of the hub. Of course, when this is done, it's difficult to maintain it in this position when the clutch is installed and the nuts are turned down. In that sense, your suggestion of using Locktite on the fine threads will be very helpful. However, I think the best plan is to obtain studs which are more suitable for the application (i.e. make a better choice of stud configuration than GM did once-upon-a-time).

A better stud will be about 1" in total length, have a fine threaded end of about 1/4", an un-threaded shank of about 1/4" and a coarse threaded end of about 1/2". The stud must be SAE grade 8. The nut and lockwasher need to be grade 8, too. And, believe me, no judge will ever know the difference (as long as you use phosphate-finished studs which most grade 8 studs will be).

Thanks so much Joe, that is the exactly problem I have, and why the studs backed out so easily when the nuts were removed. I'll head down to the local parts house