48 coupe- trying to understand head gaskets

[Bolts]

I am sure this has been discussed 1000 times, but I didn't find the answer in my searches.
Here's my question:
Listed in parts catalogs for a 59AB engine, I see head gaskets with big round water holes and some with triangular or trapazoidal shaped holes. I get that the web between the trapazoidal holes is thinner, but why are they made this way and will the two types interchange in a stock engine?
Thanks

[Bolts]

I have heard about differences in water ports in aluminum heads or water hole differences in iron heads of different years, but my question is about the use of the different gasket designs on a stock 59AB engine with 59A-B heads. Are both designs usable?

[scooder]

The trapizoid hole type are often for the 3 1/16" bore.
Martin.

[Bolts]

For the 1946-48 years Ford engineers determined that smaller water holes in the gasket were to be used for some reason. I'm wondering what the reason was?

If increased horsepower (higher compression) was the reason, that might answer my question, but I am wondering why the water holes were reduced in the 1946-1948 gaskets. The design with the big trapazoidal cutouts as shown on the Van Pelt page for the 24 stud, 3 3/16 bore engine up to 1942 were replaced by the round hole version with much smaller holes for the water to flow through in certain places on the block (head).

Does anyone know if the change in design had to do with reducing temperature variation over the head surface area and the restricted flow designed to reduce stress on the castings?

[Bruce Lancaster]

The round hole ones are right for '46-48, AND the Ford overhaul manual for '37-48 calls for prewar 24 stud engines to have a couple of center holes in heads redrilled and then the round hole gaskets installed. Presumably the purpose was to shift flow around for more even cooling...I've never laid out all the stuff together to compare what the change does exactly, though I trip over all the necessary parts daily. It probably involve forcing more water aft before it exits up through the middle...new gasket coincided with a slight change in valve angle, supposedly done to allow better water jacketing around valves.
At any rate, the details are in the Ford engine overhaul pamphlet, available through all the parts places. There are I think three editions, 1936--46-47-48. Many of the pictures involve what seems to be a wartime 239, probably Canadian, with full flow setup!
So simple answer is 59's get the round holes, earlier engines get some drilling and then the round hole gaskets. Note the front and back markings, as one feature is some slightly larger holes in rear half,

[Bolts]

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Thanks a lot Bruce. Glad you chimed in.
I got thinking that with the water pumps in front and the water exit in the center of the heads there might be some areas of the block and in the heads where the flow of coolant was different than originally thought or understood by the designers. Add to that the lack of maintenance most cars receive over their lives and some debris in the radiator and some rust and viola, heat distortion and cracked castings or blown head gaskets or both.
I've been running my engine (not driving the car) without thermostats and got to thinking that too much flow out of the heads might result in some parts of the block getting less circulation, rather than more, as I was hoping for by running without the restrictions caused by the thermostats.

[Bruce Lancaster]

The gaskets always have the final say on flow as a part that can be tuned easily by the engineers, and some holes in the blocks are sized for issues like shaking the sand out of the castings and such rather than for control of the water.