The Chevrolet “W” 348 (and 409) Engine – First Of A Long Line Of Big-Block Chevy V8s

(first posted 6/7/2012)     We tend to think of the legendary Chevy small-block engine as near-immortal, having been built for forty-eight years, from 1955 through 2003 (The LS is a clean-sheet new engine). But its big brother, the big-block Chevy V8, was built for fifty-one years, from 1958 through 2009. Yes, it got a new cylinder head with the Mark IV version in 1965, but the block was a redesign, and one can swap crankshafts (with some minor adjustments). There was a good reason for that new cylinder head; the “W” version’s was a bit of an oddball.

(from a hi-po 409)

The Chevrolet 348 cubic inch V8 engine that arrived in 1958 was an anomaly. One would expect that a larger block version of the legendary small-block Chevy that had first appeared five years earlier would largely resemble that highly successful design, especially in its well-breathing cylinder heads. But no; the first big block Chevy arrived with a rather radically different design altogether: a 16° angle on the top of the cylinder block, and perfectly flat heads; a “combustion chamber in cylinder” design. That only lasted until 1965, but the big block went on to be built for just over fifty years.

The idea behind the novel head was to maximize brake mean effective pressure (BMEP) at relatively low engine speeds, resulting in a very fat torque curve. And it was essentially the same basic idea as used by Ford for the MEL engine, which also appeared in 1958. Both of these designs were indeed known more for their torque than their top end, although with the later hi-performance big-valve/port heads, the 409 acquitted itself on the drag strip and at NASCAR very well indeed. Unlike the MEL, the Chevy valves were staggered, which allowed much more favorable porting than the tortured MEL head. Maybe port was not a preferred drink in the Ford family.

Clearly, the “W” engine was designed for duty in Chevy’s bigger trucks as well as its rapidly-growing cars. The 327 inch version of the small-block was still several years away, so the 348 was the alternative to the high-winding hi-po versions of the 283.

If one was looking for serious scoot in 1958, the horsepower difference between the 290 hp 283 and 315 hp 348 wasn’t all that great. But obviously, their torque curves were. The 283 was happiest behind a four-speed stick, the 348 made the most of their usual role behind a Powerglide (or the ill-fated Turboglide).  The not inconsiderable difference in their weight narrowed the gap even further. Which of course explains why the W engine grew to 409 inches in 1961, one year before the 327 small-block arrived. Trying to keep one step ahead of an ever-growing mouse.

image source: rick_oleson’s photostream

There was a very small run of some fifty 427 inch “W” engines, the super-stock Z-11, and intended for the drag strip. The bodies had aluminum parts, and there were dual Carter AFBs hiding under that cowl-induction intake. (Under) rated at a modest 430 hp, these ’63 Chevys could hit some 135 mph in the traps. The truck motor turns into a genuine hemi-challenger.

The Mark IV had totally new heads, although their “porcupine” staggered valves did owe much to the not-dissimilar arrangement on the “W” engine. The last production version, the Vortec 8100, was installed only in larger trucks, bringing the whole big-block family back to its origins. We rented a Class C motorhome in 2005 with a Vortec 8100, and its performance was impressive indeed. And the sound that came through the van-cab engine cover as it hammered up the mountains was suitable music to accompany the scenery. Never mind its thirst.