Ford Flathead Engines. Tony Thacker
Scat introduced brand-new cranks. Previously, everybody searched for 4-inch-stroke Mercury cranks. To determine which crank you have, use the “pinky or pencil” test: If your pinky fits, it’s a Merc; if a pencil fits, it’s a Ford.
Rods: The original factory Ford rods were heat-treated, carbon manganese steel forgings and were as good as it gets. If the ones you have are not bent, twisted, or cracked, they are ideal for a street or mild performance rebuild. If you are building a more high-performance or racing engine, I suggest new H-beam chrome-moly high-tensile forged rods from Scat. Scat also offers different crank pin sizes: 2.000 and 2.138 inches, available with either studs or cap screws.
Block Identification
1933-1936½
The 1933–1936½ block was a 21-stud, identified by three head studs on either side of the triangulated water passages. It also had a cast-in bellhousing.
Water pumps on 1933–1936½ blocks were located at the front of each cylinder head. The upper portion of the front of the block was smooth.
The 1932–1936, blocks had poured, white-metal Babbitt main bearings. The conventional insert bearing option was introduced in October 1935. Both the poured (meaning that the white-metal bearing material was literally poured into the rod and cap) and the conventional insert styles were available through 1936. This is a Babbitt block.
1936½
The late 1936 engines are desirable 21-studders, still with the triangulated water passages and integrated bellhousing, but they are really preferable because of the insert main bearings, which are much easier to replace.
The late engines had insert main bearings and retained the integrated bellhousing. They have no perfect external identification; the easiest way to spot the difference is to look for the insert tang in the main bearing cap. Note the freeze plugs in this pan rail.
1937
The one-year-only 1937 engines were 21-studs with triangulated water passages and an integral bellhousing. New for 1937 was the relocation of the water pump from the head to the block.
The engineers at Ford finally overcame Henry Ford’s intransigence and positioned the pumps where they could work in the block rather than the head, pushing rather than sucking.
1938–1940
The change to 24-stud heads came in 1938, indicated by the triangulated water passages, but now there were only two stud holes, not three. This version still has the cast-in bellhousing, but notice the raised deck for the intake.
The 1940 Mercury engine is very similar to the Ford in that it has 24 studs, a cast-in bellhousing, and a raised intake deck. However, it has a slightly larger bore, affording 239 ci compared to 221 ci, and therefore 95 hp compared to the Ford’s 85.
1946–1948
The 1946–1948 59A 24-stud is identified by the round water passages. The raised deck is gone, because it offered no tangible benefit and complicated the manufacturing process.
Most 59As have “59” embossed on the cast-in bellhousing. However, the heads are often (but not always) embossed “59A” or “59AB.”
1949–1953
This is the desirable 8BA. Note that the water passages at the very rear of the block look like elongated tears. On earlier engines, they were small round holes.
The bellhousing for automotive applications was now a bolt-on stamped-steel unit; trucks had a bolt-on cast-iron bellhousing. This block is desirable because it offers many more transmission options.
The water pump on 1949–1953 blocks is different than that on 1946–1948 engines; it has an extra water passage as indicated. The thermostats were now located in the water necks and bolted to the front of the heads.