Adding performance upgrades to the inline-six is the same as the typical V-8 performance enhancements of increasing airflow through the engine.
While the Mustang has always been revered for its V-8 performance, even today the base six-cylinder engine far outsells the V-8 model. The 200ci inline-six, first offered in the Fairlane as a four-main-bearing base engine, found its way under the hood of the new ’65 Mustang as the base engine (replacing the smaller 170ci inline-six). By that time, the engine block had been recast as a seven-main-bearing unit to dampen crankshaft harmonics, making it one of the strongest inline-six Ford bottom ends ever built. These seven-main-bearing 200ci inline-six engines are smooth-running, easy-to-maintain torque builders that get the lightweight Mustang moving with little fuss. However, today we must deal with 80 mph highway speeds, $4.00 a gallon gas, and long commutes, all of which the small-six isn’t well suited for. Giving the inline-six some oats means easier, safer merging with highway traffic, more power for maintaining those speeds, and simply making the vintage Mustang with inline-six power more fun to drive.
How to Upgrade Performance in Vintage Mustang Six-Cylinder Engines