Legends, Urban, and Others
Regarding Shop Manual, May 2014. I remember in the early 1960s I repeated the urban legend that the W motor was designed as a truck engine, but it ain't so. I did a lot of exhaustive research for "special-interest autos" in the late 1970s for an original article (the first in a collector-car magazine) on the 1958 Impala. Using one, an article in the SAE Journal; two, another article in the GM Engineering Journal, and interviews with various GM engineers that in fact the W was designed for use and introduction simultaneously in Chevrolet cars and trucks. In other words, if the W was a "truck motor," so was the SBC 265.
As the references state, Chevy engineers under Ed Cole did not feel, at that time, that the SBC could be enlarged beyond 300 inches safely, as the larger, heavier 1958s would require, and a larger block was called for; thus the original "BBC" was developed as a supplement. When you think about it, had they thought that the "mouse" would eventually grow to 400 cubes, they would not have expended the R&D money and time on another engine. As an aside, note that cousin GMC Truck Division never used the W, preferring the Buick and Pontiac V-8s instead! I drove a truck professionally for some years, and I agree that the 265-incher didn't have the torque it required to move a big commercial, though it was fitted in 1955 and 1956! The big, long-stroke six was much better; trucks don't need rpm (sic). I like legendary stuff as much as the next guy when bench racing, but the W simply was not originally designed for trucks, per se.
The 348 was definitely not the engine of choice for hot rods; during the production life of the W I recall only one lone rod repowered with the engine in Hot Rod. Despite the later winning ways of the 409 in S/S (and the Beach Boy's ballad) it wasn't much of a design. Always good for a quote, Smokey Yunick, when I specifically ask him what kind of a racing engine the W was, said, "It was a junk engine!" He also hated that the Impala frame was weak, and body design placed the harmonic balancer ahead of the spindle center line; he ran his famous 1957 another season.
I never really was a fan of the Impala line, nor the W; I also drove and raced my 1955 Delray with power-pack 265/stick and 4.11 rear, and beat some Ws. I wrote my tech recap on the W for Late Great Chevys magazine in 1979, and will send you a copy.
Wick Humble, Via the Internet
Thanks for your letter. And you are completely correct, the 348 was developed because Chevrolet needed an engine with a larger displacement for a number of applications, cars as well as trucks. I should have made that clear but the engine's origin wasn't the point I was trying to make. However, our sources still insist the original intent of the bigger, heavier engine was indeed for trucks, but when it was determined the cars that would be introduced in 1958 needed help with their heft, they got the new engine as well.
The way it was explained to us, Chevrolet wanted a powerplant that would meet their future needs so they began working on several new configurations which, during testing, were identified as engines W, X, and Y. The X and Y engines were larger displacement versions of the 265, but the torque numbers fell short of expectations. The W engine used a new block and heads and was larger and 110 pounds heavier, but it made the numbers desired. Ultimately the W design was chosen, the letter designation stuck.
While we agree neither the 348 or 409 were the hot rodder's overwhelming engine of choice, we think you're underestimating their popularity. During the late 1950s and 1960s lots of hot rodders who couldn't afford to hop up the engine in their car opted to hit the junkyard in search of a stock, larger-displacement engine as a way to increase performance. Chryslers, Cads, Buicks, Olds, and 348 and 409 Chevys were plucked from wrecks on a regular basis. With all due respect to Yunick's assessment, we would consider the 348 and especially the 409 a success in their day and find they still have a following among those wanting a vintage V-8 under the hood of their hot rod.
As for GMC trucks using Pontiacs instead of the W motors, one of the factors influencing that was marketing. All Chevrolet products were sold exclusively at Chevrolet dealerships, while GMC trucks were sold at Buick and Cadillac dealers so those franchises could have trucks as well as cars. Since GMC and Chevrolet were competitors in the truck market, GM had to make distinctions between the two and one way to do that was with the available engines. GMC called the Pontiac 287ci V-8 the GMC 288, the Pontiac 316 was the GMC 316. Pontiac 347 and the 370 with a reduced bore for 336 inches was also used. Interestingly in Canada GMC trucks used small-block Chevys.
While GMC did use Pontiac engines, the use of Buick engines also seems to be an urban myth. (GMC did have a 401 but it was a V-6. Having the same displacement as the Buick may have caused the confusion.) If you have any information to the contrary we'd love to have it to answer that question once and for all.