Pontiac Straight-8 engine

Infobox Automobile engine


name=Pontiac straight-8 engine
aka="Silver Streak"
production=1933–1954
manufacturer=General Motors
type=8 cylinder flathead
predecessor=Auto CID|251 flathead V8
successor=Auto CID|287 OHV V8The straight-8 was an eight-cylinder, in-line automobile engine that was used in production Pontiacs from 1933 to 1954. Introduced in the fall of 1932 for the 1933 models, it was Pontiac's most powerful engine at the time and was the least expensive eight-cylinder engine built by an American automotive manufacturer. During its 21 year run, displacement of the "eight" increased twice as platforms grew. It was superseded by Pontiac's new V8, the 287, in 1955.

History

The straight-8 was dubbed the "Silver-Streak" ["Silver-Streak": The name taken from a body detail peculiar to Pontiacs manufactured from 1935 to 1956, called a "silver-streak", which is a five-banded, chromed metal band that ran down the middle of the hood and trunk. Born in the Art Deco style of the mid thirties, it was meant as a visual cue to help distinguish Pontiacs from their competitors, and create the illusion of speed.] at Pontiac Division, but unlike its "flashy" name, it was anything but. During its 21 year run, which included America's three year campaign in the war overseas, and right up until it being replaced by the V8, it was considered acceptable under Pontiac's somewhat conservative management [Motor Trend Magazine, February 1965, available [http://www.pontiacserver.com/mtchiefs1.html online] ] . Powered by the "eight", a Pontiac was promoted as a likable automobile, with just enough power under the hood to get the job done in affordable luxury.

However, by the early 1950s, overhead valve V8s from sister divisions Cadillac, Buick and Oldsmobile, as well as new overhead valve V8s from Ford Motor Company and Chrysler Corporation, made the "Silver Streak" all but obsolete in power, It was a quiet, smooth running engine that served the needs of the 1930s and '40s American consumer adequately for power, if not reliability or economy, but by 1954, the engine was decidedly eclipsed not only by competing auto makers, but by General Motors' own divisions' products as well. Further hamstringing the "Silver Streak" was the aged, but cheap to produce, flathead configuration. The V8 configuration of the "Strato-Flite" 287 cubic inch engine that replaced it in 1955 did away with all the crankshaft and L-head related problems, replacing the Depression era "cheap 8" with a truly modern, durable but yet affordable design perfectly matched to Pontiac's target market. A few years later, under former Packard and Chrysler engineer John DeLorean, Pontiac became known as a performance division based upon the durable, well performing V8s that came later, all of them based upon the original 287 of 1955.

Design

The "eight" was a typical American built engine for its time, a side valve L-head, or "flathead", with a chain-driven cam. It was naturally aspirated through a "Carter" "W" series, single or dual-venturi carburetor in downdraft configuration.

Applications

During its run, the "eight" came in all Pontiacs, which included the "Special" and "Deluxe" (1936-40), "Torpedo" (1940-48) and "Streamliner" (1942-52), as well as the first six years of the "Chieftain" (1949-58) and the debut year for the "Star Chief" (1954-66).

Specifications

Compression on the "eight" started at 5.7 - 1 initially,Pontiac sales brochure, Pontiac Motor Division, 1933.] and was increased to 6.2 - 1 ratio in 1935. In 1940 it was increased again to 6.5 - 1. From 1952 to 1954 two compression ratios were specifed, 6.8-1 with syncromesh (manual) transmission, and 7.7-1 ratio with Hydra-Matic (automatic) transmission.Motor's Auto Repair Manual,Sixteenth Edition, Motor.,1953.] The engine had a remarkably low idle speed of a 450 rpm with standard transmission and 375 rpm (while in drive) for the automatic [ [http://www.secondchancegarage.com/public/608.cfm Second Chance Garage] A web based, statistical database for mid-century Pontiacs] ; a modern engine is usually tuned to a minimum 600-700 rpm. The electrical system was a 6 volt primary with a negative ground, and a conventional mechanical ignition, with the firing-order 1-6-2-5-8-3-7-4.The Pontiac engines employed a full pressure oiling system, unlike its cousin the Chevrolet.

Below are specifications as per the model year and displacement.

1933-1935 - Auto CID|223

1950-1954 - Auto CID|268

"Special"-8

At the General Motors Motorama for 1954, Pontiac debuted its all new "Bonneville Special", a concept car envisioned by head designer Harley J. Earl. The concept was equipped with the "Special"-8, a bored out, high output 268 in³ engine that was painted bright red and detailed in chrome. This was a unique configuration for the "eight", installed in the only two "Specials" ever made. Similar in appearance only, this was a high compression variant that was modified with a high-lift cam and aspirated naturally through four Carter YH side-draft, single barrel carburetors, the same used in the 1953 Corvette, under open-mesh breathers. Total output was the highest ever for the "eight", rated at convert|230|bhp|abbr=on, though some ["300 bhp, as estimated by "Special" owner and concept collector/restorer Joseph Bortz, in a filmed interview viewable at Motor Trend Magazine, available [http://www.motortrend.com/multimedia/mtvideo/c12_0605_bortz_classic_videos/ online] .] estimated it at over convert|300|bhp|abbr=on. Like the "Special", only two of these remarkable variants were ever made.

Note: Pontiac’s new V8 was being considered for use in the "Special" but was instead held back by GM marketing. They directed that the straight-8 be used, to keep the "vee" a secret from consumers for one more year until its debut the following year. ["Why the Straight-8?, explained in the same interview above.]

Footnotes

ee also

* Pontiac Straight-6 engine
* Pontiac V8 engine
* List of GM engines