Water Pump Question

[Mike M.]

The water pump on my newly purchased '65 Coupe (327/300, PG) has a water pump with a provision for a by-pass. If it is correct should there be no by pass provision? I plan to eventually pull the motor/trans and detail this pretty original car. Thanks.

[Terry D.]

Re: Water Pump Question

Mike
What does the Judging Manual say? If you plan on that kind of work you will need to buy the manual for your car.
Terry

[James W.]

Re: Water Pump Question

The water pump on my newly purchased '65 Coupe (327/300, PG) has a water pump with a provision for a by-pass. If it is correct should there be no by pass provision? I plan to eventually pull the motor/trans and detail this pretty original car. Thanks.

Mike,

The base L75 300 hp engine uses water pump casting number 3782608 without a bypass.

Best Regards,

James West

[Mike M.]

Re: Water Pump Question

Thanks. I have ordered the Tech Manual plus Perf and Judging manuals (and a shop manual.) Just don't have them yet.
Mike

[Wes S.]

Re: Water Pump Question

If its a very original car you might want to pull motor if you think you might bowtie the car.

[Mike M.]

Re: Water Pump Question

If its a very original car you might want to pull motor if you think you might bowtie the car.

I am not very knowledgeable about the termonology such as 'bowtie'. Is that for original cars? On such a car, would you not pull the engine? I am the third owner of this particular car. However, I know that the engine was rebuilt about 5-7 years ago so it has already been out of the car once. Other than that it is pretty original (down to the orig headlights.)

[Duke W.]

Re: Water Pump Question

The external bypass was only used on SHP/FI engines. The water pump has an internal bypass and the heater core circuit also acts as a bypass.

Without any form of bypass there would be no coolant flow when the thermostat is closed.

I'm not certain, but the top pad on the coolant pump may not have been drilled for a fitting on 250/300 HP engine. Or if it was, it had a plug.

Duke

[Mike M.]

Re: Water Pump Question

The external bypass was only used on SHP/FI engines. The water pump has an internal bypass and the heater core circuit also acts as a bypass.

Without any form of bypass there would be no coolant flow when the thermostat is closed.

I'm not certain, but the top pad on the coolant pump may not have been drilled for a fitting on 250/300 HP engine. Or if it was, it had a plug.

Duke

The water pump on the engine has a by-pass provision (a threaded hole) on the top but it has a plug in it. I am not sure where the part # is on the pump. The pump is likely to have been changed on this 81K mile car which is now 45+ years old. Thanks.
Mike

[Dick W.]

Re: Water Pump Question

If its a very original car you might want to pull motor if you think you might bowtie the car.

I believe Wes meant you might not want to pull the motor if it is BowTie quality.

[Rick A.]

Re: Water Pump Question

Dickie,

OP mentioned motor had already been pulled once before, so..............

[Philip A.]

Re: Water Pump Question

Mike
There should be no bypass provision. The boss on top of the water pump should be solid and not drilled and tapped for a fitting or plug. Fortunately, this is not a Corvette only part and you should be able to find a correct one.

[Joe L.]

Re: Water Pump Question

The water pump on my newly purchased '65 Coupe (327/300, PG) has a water pump with a provision for a by-pass. If it is correct should there be no by pass provision? I plan to eventually pull the motor/trans and detail this pretty original car. Thanks.

Mike-----


As others have mentioned, your application originally used a waterpump with no upper bypass (i.e. external bypass). There is a small boss on the top of a correct waterpump but it is nowhere near large enough to accommodate a drilled and tapped fitting.

The reason that you car probably has a pump with a plugged bypass fitting is that for MANY, MANY years all GM and aftermarket SERVICE waterpumps had the the external bypass provisions. So, if one purchased a new waterpump, one got one with the external bypass (and a pipe plug to plug it with if not needed). Over time, the core stock of automotive rebuilders became heavy with these external bypass type pumps. So, even if one bought a rebuilt pump, the chances are it would be an external bypass type.