Tired of replacing water pumps

[Timothy B.]

My water pump on my 67 small block is starting to leak again out of the weep hole. Just like everyone else, I have been there done that so many times over the years on pre mid 70's cars. My first experience with cars was helping my dad replace water pumps I think! Now, my car is a driver and I would really like to install a water pump that I can count on lasting. I historically get about 4 or 5 years out of a water pump regardless of mileage. My question is this: Has anyone found a good replacement water pump that looks OK once installed that can be expected to last? I understand reading other posts that GM used a smaller diameter shaft up to some point and then fixed the problem by using a larger shaft. Maybe someone has made a retrofit pump with larger shaft that will still fit my fan and pulleys? The p/n of my existing pump is 3782608. Any thoughts?

[Duke W.]

Re: Tired of replacing water pumps

Check the pulley alignment and belt tension.

These standard SAE spec automotive water pump bearings are available in two different sizes and styles. Both 5/8" and 3/4" bearings are available in ball-ball style and ball-roller style where the front roll of balls is replaced by rollers.

I've never had a 5/8" ball-ball type water pump bearing last more than 40-50K miles.

Find a local rebuilder and specifically have them use the 5/8" ball-roller bearing. They are interchangeable with the 5/8" ball-ball style. This should improve mean pump life by at least 50 percent.

Duke

[Joe L.]

Re: Tired of replacing water pumps

My water pump on my 67 small block is starting to leak again out of the weep hole. Just like everyone else, I have been there done that so many times over the years on pre mid 70's cars. My first experience with cars was helping my dad replace water pumps I think! Now, my car is a driver and I would really like to install a water pump that I can count on lasting. I historically get about 4 or 5 years out of a water pump regardless of mileage. My question is this: Has anyone found a good replacement water pump that looks OK once installed that can be expected to last? I understand reading other posts that GM used a smaller diameter shaft up to some point and then fixed the problem by using a larger shaft. Maybe someone has made a retrofit pump with larger shaft that will still fit my fan and pulleys? The p/n of my existing pump is 3782608. Any thoughts?

Timothy----


If you wish to stay with a "correct" waterpump casting configuration (which your 3782608 would be for a 1967 300 hp), you can't do much more than Duke suggests. The '608' waterpump casting will not accept a "jumbo" size bearing (i.e. the size used for all 71+ applications).

You can use an aftermarket aluminum pump like a Weiand or Edelbrock. These are designed with a "jumbo" bearing.

It's also possible to use the 71+ small block Corvette pump castings. However, they need to be modified slightly to work for a pre-71 application and they also have to be fitted with a shaft with a 5/8" pilot and a "dual pattern" hub.

[Mark P.]

Re: Tired of replacing water pumps

You might want to give Bill Mock a call. He is in the Driveline. He guarantees his pumps for life and has a definate opinion on the manufacturer of bearings (i.e. FAG) and impellers he likes to use. He has a good reputation for quality work. The pump for your application would be about $150.

[Timothy B.]

Re: Tired of replacing water pumps

Thanks for the replies. So, based on your experiences, if I were to get my existing pump rebuilt with quality bearings and parts, what is the life I should expect out of the pump? I drive the car about every two weeks around the area, and occasionally longer trips, about 2000 miles per year max probably.

Also, are there any suppliers of modified 71+ pumps as Joe suggests with the larger bearings and dual pattern hubs?

What are the desired casting numbers of the later pumps with larger bearings?

Thanks!

[Joe L.]

Re: Tired of replacing water pumps

Thanks for the replies. So, based on your experiences, if I were to get my existing pump rebuilt with quality bearings and parts, what is the life I should expect out of the pump? I drive the car about every two weeks around the area, and occasionally longer trips, about 2000 miles per year max probably.

Also, are there any suppliers of modified 71+ pumps as Joe suggests with the larger bearings and dual pattern hubs?

What are the desired casting numbers of the later pumps with larger bearings?

Thanks!

Timothy-----


Under your usage conditions I would think that a standard 55-70 style pump would last a lifetime. I don't understand why you have the need to keep replacing them.

I don't know of anyone that advertises making a 71+ style pump work for 55-70 Corvette applications, but some of the rebuilders like Bill Mock could probably do it.

There are only 2 castings for the 71+ style short leg waterpump. GM #3991399 is one and GM #330813 is the other. For a 55-70 Corvette application without external bypass, the 3991399 would have a configuration most similar to the '608' casting. For 55-70 applications with external bypass, the 330813 would appear most like the originally used castings.

[Jack H.]

Re: Tired of replacing water pumps

Let's see...I've logged +60K miles on the rebuilt 3991399 on my '71. And, there are folks in the chapter here who've gotten +30K miles out of their small shaft/small bearing earlier pumps.

Our Denver local water pump rebuilder prides himself on NOT re-using factory original shafts + using top drawer pump bearings. Mayhaps, you've been the victum of less that top draw water pump rebuild cycles...

[Timothy B.]

Re: Tired of replacing water pumps

Well here is a question for the forum: Which is harder on the pumps, time or mileage? My last two pumps each lasted about 4 years but with only probably 8K or less actual mileage on each pump.

[Joe L.]

Re: Tired of replacing water pumps

Well here is a question for the forum: Which is harder on the pumps, time or mileage? My last two pumps each lasted about 4 years but with only probably 8K or less actual mileage on each pump.

Tim-----


I would say that USAGE (i.e. "mileage") is the main factor in pump deterioration. However, regardless, IF the main factor were TIME-in-service, then it's not going to really matter whether you use a 55-70 style pump or a 71-74.