How many times haven't you seen an ad such as this;

FOR SALE: 1968 Impala SS427, buckets, 4 speed, 12 bolt posi, low mileage, rebuilt Chevy 350.............

Without the correct engine installed, an SS427 Impala is of little more value than a basic Impala, yet you see it all the time; people who want an astronomical price for a vehicle that doesn't have the original engine. Undoubtedly THE most important feature of any Impala SS427 is, of course, the engine. What follows is a summary of the 427 engines available in 1968.

 

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

Type
Cubic Inches
Horsepower
Block #
Main
Engine Suffix Code
V-8
427
425
3916321(early)*
4 Bolt
ID
V-8
427
425
3935439(late)
4 Bolt
ID

*Denotes that this block was used only until January of 1968.

 

First introduced in 1966, the L-36 continued to be a full-sized mainstay in 1968. It was the primary engine available for all the big Chevrolets, and was the featured engine in the SS427 option. It was changed only slightly from 1967 and continued to crank out a very respectable 385 horsepower. The L-36 was installed in 4,081 of the full-sized cars in 1968 and was referred to in the dealers brochure as "Chevrolet's top power in 1968". Notice the positioning of the snorkel on the the '68 L-36 engines pictured above, how it points straight down to the passenger side wheel opening. This particular arrangement caused a lot of negative feedback from customers, as it led to a lot of airborne dirt and grime being sucked into the air cleaner assembly. These complaints eventually led to the 1969 engines having their air cleaner assemblies reworked so the snorkel would point towards the battery, an area of the engine compartment supposedly less vulnerable to picking up airborne contaminants.

Some of the minor changes incorporated into the 1968 L-36 included the use of a spin-on oil filter for the very first time and the use of exhaust heat riser ducting. This ducting was routed from the passenger side exhaust manifold and into the snorkel of the air cleaner. This can be seen on the engine to the left, which also shows the correct style of air cleaner lid for an automatic transmission car. The engine to the right shows the correct style for the 4-speed cars. The only visible difference between the two is the "Auto-Thermac" heat riser on the auto transmission car.

1968 L-36 AS INSTALLED IN THE IMPALA SS427

Type
Cubic Inches
Horsepower
Block #
Main
Engine Suffix Code
V-8
427
385
3916321 (early)*
2 Bolt
Auto Trans-IJ Manual Trans-IE
V-8
427
385
3935439(late)
2 Bolt

Auto Trans-IS Manual Trans-IH

*Denotes that this block was used only until January of 1968

All information provided through the exhaustive research of Mr. Alan L. Colvin in his book "Chevrolet by The Numbers: 1965-69".