Names and Numbers
In the performance and racing business, we're used to numbers. Everything is judged by numbers. Horsepower numbers and air flow numbers, top speeds, lap times, elapsed times, and on and on. And then the names seem to come with the numbers, like Hemi and Wedge and smallblock, etc. Then we put the numbers and names together, like 426 Hemi, creating a title or a nickname, and from then on that's what it's called.
Without doing a lot of historical research, it seems like this situation began developing almost as early as the car business itself, and certainly from the time cars became available from more than two manufacturers to choose from. Later, the number of cylinders and engine displacement were the most common uses for names and numbers. Straight 8, V8, "A" engines, "B" engines, 340 cubic inches, or V10.
As the musclecar era was about to begin in 1962 and the horsepower race was in full swing, Chrysler was faced with a problem. We had been building the 413 for several years, but we wanted a name for the new hot rod package. "Let's call it the Maximum Performance Wedge!" Chrysler already had a 413, and it was a wedge, so "Wedge" by itself was not enough. Maximum Performance was fine, but it made the name quite long. So, they introduced the Stage I. In 1963, it became a 426 and the Stage II, and in 1964 it became the Stage III. All were Max Wedges, as its nickname became known with time. In 1978, the next generation of performance "B" engine cylinder heads were introduced-the last pieces machined on the B/RB assembly line in Trenton, Michigan-as the Stage IV. Then, in 1991 the Stage V head family was introduced-P4529993-all five of these heads are cast iron. Then, the Stage VI head-P4529335-was introduced as the raised-port, aluminum head.
Much lesser known were the Stage I and Stage II versions of the 426 Street Hemi. The original '64 Hemi was considered the "race" Hemi. It was also used in 1965 and again in 1968 in the A-Body cars. The Stage I 426 Street Hemis were the '66-'67 models, while the Stage IIs were the '68-'69 models, featuring a larger cam. The original '64 cast iron Hemi head is generally called a "K" head. The aluminum version of this head, introduced in 1965, was called the A990, which was the name for the whole '65 Race Hemi package. In 1966, production went back to the cast iron head, which was used for the Street Hemi engines, this head staying through 1971. This cast iron head can be considered the D1. The next version to go public was around 1970-'71, and was called the D4. It was also cast iron, but was not used in the production cars, only NASCAR. The drag racers used an aluminum head they called the D4A because it was ported to match the D4. A couple years later, a round port version was introduced called the D5, and then the last of the '70s-era Hemi heads were called the D6, which was also made in aluminum. The cast iron Hemi head-P4529898-and the aluminum Hemi head- P4529336-that Mopar makes today are considered D8s. During this same period of time, there were about three, perhaps four, versions of the various blocks, Hemi, and wedge, but they didn't really get official nicknames. Naming the blocks became very important in the smallblock.