V6 water pumps getting hard to find

[Troyport]

Here's some pictures of the 3 different pumps. I have no affiliation with this ebayer, but I think it is the cleanest way to see the differences. There's also a really inexpensive one that has the bigger gussets, kinda looks like the medium duty, but it is made out of aluminum and therefore very light duty. Keep in mind I am no expert, I could be totally wrong. Would love any feedback - P.S. - on my previous post, I said the light duty water pump is for "manual power steering". I meant to say "no power steering"

heavy duty.jpg

medium duty.jpg

light duty.jpg

[BobBray]

My '67 351E (no power steering originally) had the iron pump with the short gussets on it before I rebuilt the engine. No idea if it had ever been changed. I replaced it with a NAPA 42099 which is iron with the long gussets like the one in the second picture. The NAPA 40299 appears to be identical to the GMB 1302835. The 1967-68 GMC light duty parts catalog shows part #8875385 as the water pump for all 305 and 351 V-6's.

[Troyport]

Hi Bob, yes, that GMB1302835 does appear to be the correct pump, that is the heavier-duty of the light duty pair. Looks like that is no longer available, at least from what I can see. Summit claims to have it in stock, until you click the box, then there is an estimated delivery date of a few weeks out. I called them, and they could give no definitive answer. If someone knows where to get them, especially for the price of around 60 bucks, I sure would love to know! Or, if someone just put on the lighter-duty pump in place of this one, I would also love to know how it worked out. Since this truck is no longer a farm workhorse, I figure it would be just fine. Heck, could buy 2 for the price of the rebuild kit on ebay if they don't last long. Or again, relocate the power steering pump to just run off the crank. What does everyone else do?

[LEWISMATKIN]

Originally Posted by troyport

here's some pictures of the 3 different pumps. I have no affiliation with this ebayer, but i think it is the cleanest way to see the differences. There's also a really inexpensive one that has the bigger gussets, kinda looks like the medium duty, but it is made out of aluminum and therefore very light duty. Keep in mind i am no expert, i could be totally wrong. Would love any feedback - p.s. - on my previous post, i said the light duty water pump is for "manual power steering". I meant to say "no power steering"

Attachment 10154

Attachment 10155

Attachment 10156

the top pump is for engines with air brakes, the lower is for engines w/o air brakes

[lizziemeister'sV6]

Correct me if I'm wrong - but I'm pretty sure 1955 - 1963 Pontiac V8's share the same water pump as the GMC V6 lighter-duty engines.

[BobBray]

The Pontiac pump looks similar but does not interchange.

[lizziemeister'sV6]

Thanks Bob - had an old timer tell me that when he inspected my 65 Suburban - said GMC used Pontiac V8's in the late 1950's and they carried on the use of the same waterpump when the V6 was developed.

[LEWISMATKIN]

The pontiac pump had a different impeller---all aftermarket replacement new pumps use the gmc impeller in both applications. I have had both and the gmc pump will install on the early '63 pontiac timing cover.

[lizziemeister'sV6]

Originally Posted by LEWISMATKIN

The pontiac pump had a different impeller---all aftermarket replacement new pumps use the gmc impeller in both applications. I have had both and the gmc pump will install on the early '63 pontiac timing cover.

If I'm understanding it right - a NOS Pontiac pump will not work on a GMC because of the impeller clearance - but an aftermarket pump will fit either the Pontiac and GMC - so the housings are the same. Is the Pontiac impeller deeper, larger around or what. So the old guy was correct in a way.

[LEWISMATKIN]

the pontiac impeller has somewhat taller blades, they are shorter in length, and are turned the opposite direction than the GMC pump. the pontiac impeller also has 3 large holes that surround the hub of the impeller.