I bought a model A which had been started as a hot rod project back in September. I have been finishing it since then and recently got it drivable and have been continuing to work on it. I noticed yesterday that it was getting hot after driving a couple of miles. I started looking for possible causes and I noticed something quite odd. This is a 59A motor but the water pumps on it are for the 8BA and have an additional water passage at the top of the pump. Since there is no corresponding port on the 59A block, these ports have been plugged with a brass pipe plug and filed flat, I am wondering if this could be the cause of my overheating issue. Thank you for your patience, this is my first flattie and I have a lot to learn.
That's not the cause of your heating issues. Been using that style water pumps on many 59A flatheads for a long time never any issues. Overheating flathead could be caused by a number of things especially if the water passages inside the block in the area of the two rear cylinders on each side are filled with crud. Its one typical issue for an old block the crud builds up over time even if its a new build if that area of the block water passages have not been cleaned correctly issues can developed. Ronnieroadster.
Flush everything. Engine, radiator. Likely crud mucking up the works as Ronnie said. Fixed my overheating issue.
I can attest to the fact that even after getting my short block (59A) back from the machinist there was still quite a bit of crud in the block. They didn’t have a fancy steam or other type of cleaner. I had asked them about that before they started work, but he was one of few a machinists left that knew flatheads. About a year after they finished my engine, the shop closed it’s door.
Another potential issue is having too little spark advance. Some of the stock distributors don't have enough mechanical advance. If the "crud cleaning" process doesn't resolve the issue - you might send your distributor out and have it gone through. You can contact Mike at ThirdGen Auto . . . he can get you sorted out.
Be aware that the original pumps were oiled by little passages that run down from the pressure relief valve at the front of the valve chamber. I don't know if that would cause any problems using 8BA pumps. 8BA pumps use sealed bearings. If I was doing it, I would have the radiator tanked and rodded out, first thing. I have repeatedly posted what that rust in the block can do to a radiator and how to fix it.
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