1965 Chevelle SS396 Z16: 201 Built, And A Common 396 Engine Misunderstanding Finally Resolved

Automotively speaking–as well as in many other arenas–I’m a “Jack of all trades, master of none” sort of guy. After about the fifth or sixth Chevy engine L-code variation, I start to get a bit glassy-eyed. But I’m always eager to fill in the details, especially when they correct one of my mistakes. As usual, it was a commenter (Terry Boyce) who pointed out that I had made a commonly repeated mistake about the the 1965 Chevy 396 engines the other day. Time to set the record straight, and we’ll use the legendary 1965 Chevelle SS396 Z16 as the vehicle to do it in.

A brief recap: the new Mark IV “porcupine” 396 CID engine arrived in the early months of 1965, and was available as a production option in the Corvette and full-sized Chevrolets, in L78 425 hp form. That meant aggressive solid-lifter cam, big valves, rectangular ports, 11.0:1 compression, and all the other best goodies available at the time. All of 2157 Corvettes and 1838 full-sized Chevys were built with L78s under the hood (any Caprices?).

But Chevy also wanted in on the mid-sized action, where the Pontiac GTO had created a whole new genre. Their response was the mid-year 1965 Z16 SS396, of which only 201 were built. They were never advertised, although they got plenty of publicity otherwise. Dan Blocker (“Hoss” in Bonanza) was one of its big fans. Why Chevy didn’t put the SS396 into production in 1965 is a good question, and I’m surely not the first to ask. It was a wickedly fast machine, and those that got their hands on one were highly enthusiastic.

The ’65 Z16 was a much better car than the actual production ’66-up SS396. It was built on the reinforced convertible frame, and had unique chassis components including the biggest brakes from the full-sized Chevy line. The ’66 SS396’s chassis was mostly unchanged from the mild regular V8/SS coupes, and was decidedly not renowned for its handling or brakes. It was built to a price, to undercut the GTO.

Under the hood is the source of the 396 confusion. The Z16’s engine was rated at 375 hp, and since the legendary solid-lifter L78 375 hp 396 became available on SS396s as of mid-year 1966, and was also the top engine on Camaros and Novas during the 1967-1969 heydays, I — as well as probably a few others–mistakenly assumed that the Z16’s 375hp engine was also an L78. Not so!

It was actually an L37, made only for those 201 Z16s (as far as I know). The difference? The L37 had a hydraulic lifter cam, somewhat less aggressive in its lift and duration too. Someone correct me if I’m wrong (again), but it appears that the only difference between the 375 hp L37 and the 360 hp L34 was that the former had 11.0:1 compression and the latter had the a more civilized 10.25:1 CR. Which makes me wonder if the they had the same heads? Did the L37 have the rectangular port heads, and the L34 the oval-port heads? Or did both of them have oval-port heads? Chevy “L” experts; where are you in our moment of need?

One of the most distinctive features of the ’65 Z16 was the rear-end treatment, which was different from the cooking SS models. The black trim was unique, and those tail lights are from a 300 Series Chevelle.  Don’t even ask what these cars sell for nowadays.

A couple of remaining questions and factoids on the early Mark IV engine. If the hydraulic cam L37 Z16 engine “made” 375 hp, then why was the solid lifter L78 engine also rated at 375 hp, when it was essentially the same engine as the 425 hp version in the Corvette and big Chevys. Well, the 425 hp rating was undoubtedly closer to the truth, although the Chevelle versions did use a slightly different exhaust manifold to fit in its engine bay.

And if the L78 396 made 425 hp, how come the essentially identical but larger displacement 1966 L72 427 was rated also at 425 hp? According to some sources, Chevrolet fully intended to give the L72 a 450 hp rating, which it undoubtedly actually made with its extra 30 cubic inches, but then got cold feet as the insurance industry was beginning to raise the issue of big hp numbers in a big way. Realistically, the insurance industry was the primary source of all the hp rating “gaming” that went on for the next several years, like the 430 hp L88. With its 12.5:1 CR and other race-ready parts, it undoubtedly made closer to 500 hp.