Water pump housing: Casting 2780987, p/n 2780988

[a6t9vette]

Looking for a water pump housing Casting number 2780987, p/n 2780988, with 5/8" thread for both heater hose lines. It seems like all the after market ones have one 1/2" and one 5/8", which doesnt match the heater core. If anyone has one laying around in the garage please and would be intrested in selling please let me know.

Thanks,
Bob

 

[Big John]

I think the threaded holes are the same on all of them. The hose nipples are different sizes.

 

[a6t9vette]

Per a reference I found it looks like the changed the casting in 70, and then back to the 69 and earlier design in 71

http://books.google.com/books?id=0LYGoE ... q=&f=false

Im not sure what is up with mine, the the nipple and threaded hole are visably different, the top hole its hard to tell with 40 years of corrosion but after cleaning up with a wire brush I dont think the smaller nipple would ever even come out. Since my heater core has both the same size ports this makes putting the small hose on a large heater core nipple a pain, never mind I think it looks funny with two differnt hose sizes. I'll try to take a pic later to show everyone what im talking about.

 

[Big John]

OK, I stand corrected. The holes in the water pump are different sizes. One is 1/4" NPT (for the 1/2") and the other is 3/8" NPT (for the 5/8"). The early housings are tapped for 3/8" NPT pipe thread.

If you can't find one, a few minutes with a drill press and a pipe tap would take care of your issue.

 

[a6t9vette]

Yea I guess i was referenceing the hose size instead of the pipe thread. I measured the two nipples on my pump housing and referenced those to sits for pipe spec, and I came out with one a 1/4" pipe and the other at 3/8. Whats strange is based on the casting number I should have both 3/8, it doesnt look like an adaper of any sort was used either. Who knows what kind of shade tree job might have been done since 69....