346 Flathead

346 Flathead

Brief History

The Cadillac 346 Flathead V8 was the durable monobloc V-8 that would go on to help win the war. The 346 Cadillac flathead was the power plant of choice for  the U.S. Army’s M-5 and M-24 tanks. The engine was backed by a  Hydra-Matic, which was an exclusive Cadillac option new for 1941, which also saw action during World War II. Cadillac engineer Harry Barr would later recall that the transmission was very serviceable right from the start, and the improvements resulting from four years of military service would make the postwar versions even better.

In the mid to late 1930′s Cadillac also built a 322 flathead V8 which is very similar to the Cadillac 346. The difference between them was the 346 bore size is 1/8 inch larger. Both engines were designed by John F Gordon, he would later go on and become the COO of General Motors from 1958 to 1965. At the time, the Cadillac flathead possessed some of the finer mechanical accomplishments for an engine. It used pressed-in piston rings (which became an industry standard). The engine also allowed for hydraulic valve adjustment which was state of the art at the time.

Dry Lakes and Hot Rods


There isn’t much information about the Cadillac 346 during the pre-war days. I’m guessing the engine was rather new and did not show up in the local wrecking yards for some speed thirsty guy to find and the odds of a fancy new Cadillac being sold off for parts to private parties was probably rare. That being said I have seen several old photographs with dry lake style cars running the Cadillac 346. Keith Landrigan had a 1932 Ford Roadster that ran a 346. I believe the car is on the cover of the 2nd or 3rd Hot Rod Magazine. His roadster ran a recorded run of 115.83.

Photo by Howard Gribble

Photo by Howard Gribble