1968 saw the return of the "Special High Performance" L-72, 425 horsepower, fire-breathing 427 as the top of the line engine for the full-sized lineup. It was not available on a full-sized Chevrolet in 1967, and Chevrolet did not go out of its way to announce its availability in 1968 either. Available on all the full-sized Chevrolets, the L-72 wasn't listed in the Chevrolet sales brochure as an optional engine. An 11 to 1 compression ratio, solid lifters and cam, forged pistons and crankshaft, and an aluminum intake complimented by a huge Holley carburetor made for a very serious street engine that was better suited for the strip. 568 of these powerhouses found their way into the big Chevys, but it's anyone's guess as to how many of those were SS427 Impalas. Chevrolet did not keep that strict of records, but it's a good bet that the majority probably went into Biscaynes for strip duty. The L-72 equipped SS427 option cost $542.45.
Included with the SS427 were what Chevrolet described as "chrome on rocker arm covers, air cleaner and oil filler." A correct L-72 is pictured in the photo to the far left, featuring the same open-element style air cleaner that the other high-horsepower, solid lifter Chevrolet engines received.
Also shown above and in the center is another 1968 L-72 that features an over the counter dealer installed fresh air induction system that is similar to, but not the same as, the type used on Camaros that year. This is the only example of this setup I have ever seen. The SS427 that this engine is installed in can be seen in more detail in the 1968 Photo Gallery.
The additional options section of the 1968 Chevrolet dealers order form shows the L-72 listed twice, once in conjunction with the Z-24 Impala SS427 option. This can be seen by clicking on the thumbnail above and to the right.
THE 1968 L-72 AS INSTALLED IN THE IMPALA SS427