[Terry Burtz, Calif]

Cylinder and exhaust port #4 run hotter than the other cylinders and exhaust ports. I believe this is due to reduced cooling water flow in this area.

The original Model A cylinder block castings (A-6015) have a large elongated hole between cylinders 2 and 3 that are open to the water jacket. This hole is the result of a core print that was used to support the water jacket core during the pouring of the casting.

When I look at the Parts Index on the MAFFI site, I see that the head (A-6050) and cylinder head gasket (A-6051) both changed during production to have an A suffix.

I'm thinking that early heads (A-6050 without a suffix) did not have the large elongated hole between cylinders 2 and 3.

I'm also thinking that later heads (A-6050-A) had the large elongated hole.

When the large elongated hole is present in the head and cylinder head gasket, cool water entering the cylinder block can take a shortcut through the elongated hole, and the flow around cylinder and exhaust port #4 will be reduced.

My thoughts are that cylinder and exhaust port #4 will run cooler if the large elongated hole is not a through passage.

Perhaps the change was made to prevent water pump cavitation without considering what would happen to water flow around cylinder and exhaust port #4.

It would be interesting to see the difference in temperature if the same engine were run with heads with and without the elongated hole and have the temperature measured with an infrared thermometer.

Please comment, and if anyone has access to the archives, that would be additional information.