Although Chrysler made a lot of really good engines over the years, two come to mind as legendary: the 426 Hemi and the Slant Six. While the Hemi and its variations are the engines still to beat at drag races, the Slant Six is best known for its indestructibility because of its ability to commonly run over a half a million miles without a rebuild.

For some who think that replacing the Slant Six engine with a V8 one of the best performance upgrades for an A-body, this is not true. In fact, the Slant Six is a performance engine with a proud racing heritage. The following is an excerpt from the Slant Six Racing Manual of the Direct Connection Engine Performance Book:

The Slant Six engine was introduced in 1960 in two versions -- 101 hp, 170 cu. in. and a 145 hp, 225 cu. in. From this modest beginning, the Slant Six built its reputation for performance and reliability. The 148 hp, 170 cu. in. Hyper-Pak introduced in the 1960 Valiant was the next step and the one that was to prove the new engine worthy of any performance challenge.
In 1960 with the introduction of the new compact cars by all the American automobile manufacturers, NASCAR sanctioned a special race exclusively for the little 6 cylinder powered compact cars. The race was held in Daytona and had seven Slant-Six Valiants entered. When the race ended, not only had all seven Hyper-Paks finished proving their reliability and durability, but they won the first seven places! This type of performance speaks for itself.

Anthony Young wrote about that race in his book Mighty Mopars 1960-1974:

"When NASCAR decided to run a compact road race in conjunction with the 1960 Daytona 500," recalled Dick Maxwell, "all the factories got involved. We built a fleet of seven Hyper Pak Valiants with 148-hp 170 ci sixes having a single four-barrel with ram manifold. It was a Plymouth runaway. We finished first through seventh. Our cars were so fast, NASCAR never did that race again."

While replacing the Slant Six with a 318 or 360 is fairly common, it is not cheap. There are several changes that must be made over and above the cost of the new engine, transmission, and possibly axle. With gasoline prices the way they are today, a performance upgrade of the Slant Six can add significantly to its power while maintaining or enhancing its already excellent fuel efficiency. For those who like driving through twisty mountain roads, the Slant Six powered cars also handle better than V8s due to their superior weight distribution.