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I've got a 1937 Sport Coupe. The original engine was replaced in 1947. That engine was removed and a NOS block was purchased from Kanter. All the machine work was done and crank,cam and valve train are assembled. I'm working on the front of the engine and found the water pump that was on the old engine is not the correct water pump. It was cobbled onto the original engine. I'm wondering if the blocks are '38 or newer which seems to be a different water pump.
Can somebody tell me the difference between the two engines so I could get the right pump?

The 1937 120 water pumps are different from the 1938. The '37 has a string-type packing, a packing nut, and plain bushings. The 1938 pumps have ball bearings and a mechanical seal with no packing nut. The two pumps are also different where they attach to the block, and the pump to block gaskets are different. I think the '38 pumps have a larger shaft, too, so the fan and pulley would be different. An NOS block may have had the original engine number stamped on it, but any casting dates should indicate if it is a later block.

Thanks TX. I have finally done some "figuring out".
It's picture time. I've used the water pump back plate to attempt to understand what I'm working with.

The engine I removed was a '38 or newer with a '37 water pump buggered on to it. The 2 arrows point to the difference in mounting. The bolt that went into the bottom hole held the pump in place without going through a hole in the water pump housing.





The block that is going in is a '37 or older block. The plate lines up now but there is an additional hole. Does anybody know what the purpose of the hole is?

I believe that hole lets some water circulate through the head before the thermostat opens. You will see in my attached image, although it is a newer 327 block, the hole matches with one that can be seen at the top of the block that feeds into the head. That is my guess anyway and it should be cleaned out for good circulation.
Hope this helps,
Bob J.

Attach file:

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  water distribution tube-in place.JPG (215.94 KB)

The extra hole is a water bypass. It is intended to allow some water to circulate within the block when the thermostat is closed. A '37 plate and gasket should allow the hole in the plate to line up with a non-threaded hole in the block that is just above the main water inlet in the block where the distribution tube goes. The '38 and newer blocks may have this extra bypass hole located farther above the main inlet hole in the block. The '37 bypass hole is centered about 1/2" above the inlet hole in the block. A '37 pump should line up with it on a '37 block. The shop manual has some service text and pictures on the various pumps used that might be helpful. The service manuals for the '37 and '38 cars are available in the Literature Archive on this site. Be sure you are looking at the right material for your car's year and model.

In the top picture, it appears there is a hole in the block and the back plate straight above the water distribution tube, but that hole appears to be higher than my 1937. In the bottom picture, it looks like the backplate is covering the hole because the hole in the block is lower.

So, I’m thinking you don’t have the correct back plate for the block.

Here is a picture of my block with the pump removed.

Here is another photo of the back of my water pump when I removed it. You can see that the hole in the gasket and backplate are in the same position as the block.




Also, referencing the comment by TxGoat, In some cases the hole doesn’t have anything to do with the coolant flow with a thermostat closed. For example, my car being a 138CD, there was never a thermostat at the block to limit coolant flow. Instead, my car used a thermostat in the radiator to limit air flow that opened the grill louvers. There was no thermostat to limit coolant flow. For the 1937 120 line, the CDs got “upgraded” with the thermostat for the grill louvers.

My '37 engine looks exactly like Don B's. I'm pretty sure all the blocks and water pumps had the bypass hole. I believe a thermostat could be used in a car with or without the thermostatic louvers. The correct thermostat at the water outlet would assure quick, even warm-up, and the thermostatic louvers would further contribute to fast, even warm up and help retain engine heat when the car was parked in cold weather. My car is a 120 C and it does not have the thermostatic louvers. I wish it did have, but finding all the parts needed in good good working condition would be difficult. I think I'd need the entire louver assembly, the thermostatic louver motor and linkage, and the correct radiator.

The copper washers for the bolt heads are important. They function as gaskets to prevent coolant from leaking at the head bolts. Lock washers are not used with the copper washers.

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Yes, there were be a lot of parts, but there is no thermostatic louver motor. The louvers/linkage spring loaded to hold the louvers closed. When, the thermostat reaches temp, it pushes a the linkage to open the louvers. I just recently got mine working and it’s really fun to see it work.

Back to the topic, though. I still looks to me like the backplate is not correct.