1938 Only 24 stud
Things get interesting again in 1938 since Ford returns to producing different engine types side-by-side in the same model year. As mentioned in the previous section, Ford continued 21 stud motor production through the 1938 model year, but Ford also started production of 24 stud motors for use in the 1938 model year. These one year only partial production motors are unusual. They are identical to the late 21 stud motors except that the stud at the bottom of the cylinder bore has been replaced with two studs on either side of the cylinder bore. The crankshafts, rods, bearings, cooling passages in the decks, and everything except the number of fasteners holding the heads down is the same as the late 21 stud motors. These 24 stud motor occasionally confuse people who incorrectly expect the crankshaft and bearings to be like all other 24 stud motors starting the next year. The reason for the change in stud count becomes apparent in 1939. If you happen across one of these motors don’t expect to build a performance engine with it, the cylinders don’t take large over-bores and the later crankshafts take a whole lot of work to drop in. If you happen to have read the article of the work taken to make a 255 cubic inch late 21 stud motor for the Great American Race in the 1990s, just apply all that same effort to the first 24 stud motors.
These series engines got the 81 identification since they started in 193
8 and displaced 22
1 cubic inches.
Features of the 1938 only 24 stud
- 24 studs retaining the cylinder heads
- Water pumps in the block
- The water drains are angled
- Passes the pencil test
- Core plugs in the oil pan rails
- Crankcase ventilation
- Insert main bearings 2.399” diameter retained by studs
Here is a picture of a 1938 24 stud motor. The cylinder heads are one year only, featuring a cast in part number on the face of the heads. The battery cable is not supposed to attach to the middle head stud.
Here is a picture of the “pencil test” being performed on a 1938 24 stud. The pencil is resting on the front of the block just behind the timing cover. If you can do that your engine passes the “pencil test”; make sure you are not resting the pencil on the timing cover itself. You can also see the short crankshaft common to small insert main bearing crankshafts and blocks.
