67 versus 63/64 waterpump - what's the difference

[Donald H.]

My 1967 L79 has a water pump with casting 3839175 with the bypass. I know the correct water pump is casting 3859326. What is the differences in these two pumps?

I got the 67 a week or so back and am flushing the coolant system, radiator and block. Looks like about 20 years worth of rusty crud coming out. I just wondering if I should change the pump while I have stuff off and the system drained. No plans to have this car judged.

Thanks,

Don

[Leif A.]

Re: 67 versus 63/64 waterpump - what's the difference

I would absolutely change out both the water pump and thermostat while you' flushing the system. Truth be told, if it is a gunky as rusty as you say, you may want to have the radiator boiled and checked for integrity. Sure better than having a "run hot" issue 100 miles from home. Also, don't forget to put fresh belts on while you're at it. Nothing like a little bit of preventative maintenance...especially going into the warmer months.

[Joe L.]

Re: 67 versus 63/64 waterpump - what's the difference

My 1967 L79 has a water pump with casting 3839175 with the bypass. I know the correct water pump is casting 3859326. What is the differences in these two pumps?

I got the 67 a week or so back and am flushing the coolant system, radiator and block. Looks like about 20 years worth of rusty crud coming out. I just wondering if I should change the pump while I have stuff off and the system drained. No plans to have this car judged.

Thanks,

Don

Don-------


The differences between the 3839175 casting and the 3859326 casting are extremely minor. In fact, the biggest external difference is the casting number alone.

From a performance standpoint there is absolutely no difference between the two pumps. In fact, for many years GM supplied SERVICE waterpump assemblies using both castings under the same part number.

Notwithstanding the above, if the pump is old, replacing it is a good idea. These 5/8" shaft waterpumps are usually good for only about 50,000 miles maximum.

[Donald H.]

Re: 67 versus 63/64 waterpump - what's the difference

Thanks all, I've ordered a freshly rebuilt pump.

[Stan E.]

Re: 67 versus 63/64 waterpump - what's the difference

No date on 63-4, check your rebuilt.

[Duke W.]

Re: 67 versus 63/64 waterpump - what's the difference

Don-------



Notwithstanding the above, if the pump is old, replacing it is a good idea. These 5/8" shaft waterpumps are usually good for only about 50,000 miles maximum.

Pump bearing life can be extended at least 50 percent by replacing the SAE 5/8" ball/ball bearing with a SAE 5/8" ball/roller bearing. These SAE standard bearings are interchangeable, but the ball/roller has rollers in the front position instead of balls and it will handle higher loads and speeds longer than the standard double row ball bearing.

SAE 3/4" bearings are also available in ball/ball and ball/roller.

IMO it doesn't make sense to ever rebuild a pump with anything less than a ball/roller bearing. The price difference is noise level compared to the time and expense of a water pump replacement. I don't think most pump vendors use the ball/roller, but it's something you should insist on.

Duke

[John D.]

Re: 67 versus 63/64 waterpump - what's the difference

Not sure I'd want to boil out an aluminum radiator. My 67 has the original sept 66 radiator in it that appears to be held together by the crud and salt deposits. I have a dewitts to put in when the weather gets better..