Pontiac Straight-8 engine
From Wikipedia, the free encyclopedia
| Pontiac straight-8 engine | |
|---|---|
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| Manufacturer | General Motors |
| Also called | Silver Streak |
| Production | 1933 to 1954 |
| Predecessor | 251 in³ flathead V8 |
| Successor | 287 in³ OHV V8 |
The 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 most inexpensive eight-cylinder engine to build by an American automotive manufacturer. During its 19 year run, displacement of the "eight" increased twice as platforms grew. It was superseded by Pontiac's new V8, the 287 OHV, in 1955.
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[edit] History
The straight-8 was dubbed the Silver-Streak[1] at Pontiac Division, but unlike its "flashy" name, it was anything but. During its 19 year run, which included America's three year campaign in the war overseas, and right up until it being replaced by the "vee", it was considered acceptable under Pontiac's somewhat conservative management[2]. 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, OHV V8s from sister divisions Cadillac, Buick and Oldsomobile, as well as new OHV V8s from Ford Motor Company and Chrysler Corporation, made the "Silver Streak" all but obsolete in power and reliability. 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 GM's own divisions' products as well. As with all "straight 8" engines, the "Silver Streak 8" was beset with crankshaft harmonic vibration problems that would cause crankshaft breakage or excessive main journal wear. Adding to the problem was the propensity for the block to "sag" over time, making crankshaft journals off center, exacerbating the already weak crankshaft's propensity to break at the main journals. An accessory sold by Pontiac dealers in the late '40s and into the '50s was a bolt on brace, the purpose of which was to try to reinforce the overly long block. Rare was the "Silver Streak 8" that made it to 80,000 miles or so without either a crankshaft failure or a rebuilding. Further hamstringing the "Silver Streak" was the aged, but cheap to produce, flathead configuration. The V8 configuration of the "Strato-Flite" 287 cu. in. 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.
[edit] 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.
[edit] Applications
During its 19 year 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).
[edit] Specifications
Compression on the "eight" started at 5.7 - 1 initially,[3] 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.[4] With an engine idle speed of a remarkably low 450 rpm with standard transmission and 375 rpm (while in drive) for the automatic.[5]. 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. This added somewhat to its durability over the bare-bones Chevrolet "Blue Flame" 6, but its long crankshaft and unreinforced cylinder block led to crankshaft related problems.
Below are specifications as per the model year and displacement.
[edit] 1933-1935 - 223 in³
| Year | Model name (number) | Displacement in³ ( L) | Output bhp (kW) @ RPM | Torque ft·lbf (Nm) @ RPM | Carburetor series (bbl) | |
| 1933 | Eight | 223.4 (3.7) | 77.00 (56.67) @3600[3] | N/A @ N/A | Carter W-1 (1) | |
| 1934 | Eight | 223.4 (3.7) | N/A @ N/A | N/A @ N/A | Carter W-1 (1) | |
| 1935 | Eight | 223.4 (3.7) | 84.00 (61.82) @3800 | 153.00 (207.47) @1600 | Carter W-1 (1) | [4] |
[edit] 1936 - 232 in³
| Year | Model name (number) | Displacement in³ ( L) | Output bhp (kW) @ RPM | Torque ft·lbf (Nm) @ RPM | Carburetor series (bbl) | |
| 1936 | Eight | 232.3 (3.8) | 87.00 {64.03) @3800 | 161.00 ( 218.32) @1600 | Carter W-1(1) | [4] |
[edit] 1937-1949 - 249 in³
| Year | Model name (number) | Displacement in³ ( L) | Output bhp (kW) @ RPM | Torque ft·lbf (Nm) @ RPM | Carburetor series (bbl) | |
| 1937 | Eight | 248.9 (4.1) | 100.00 (73.6) @ 3800 | 172.00 (233.23) @ 1600 | Carter W-1 (1) | [4] |
| 1938 | Eight | 248.9 (4.1) | 100.00 (73.6) @ 3700 | 172.00 (233.23) @ 1600 | Carter W-1 (1) | [4] |
| 1939 | De Luxe 8 | 248.9 (4.1) | 100.00 (73.6) @ 3700 | 172.00 (233.23) @ 1600 | Carter WA-1 (1) | [4] |
| 1940 | Deluxe[6] | 248.9 (4.1) | 100.00 (73.6) @ 3700 | 175.00 (237.3) @ 1600.00 | Carter WA-1, WD-0 (2) | |
| 1941 | Custom & Torpedo Streamliner 8 | 248.9 (4.1) | 103.00 (75.8) @ 3500 | 190.00 (257.64) @ 2200 | Carter WD-O (2) | [4] |
| 1942 | Streamliner[7] | 248.9 (4.1) | 103.00 (75.8) @ 3700 | NA (NA) @ 2000 | Carter WD-0 (2) | |
| 1946 | Torpedo (27LA78)[8] | 248.9 (4.1) | 107.00 (78.74) @ 3700 | 190.00 (257.64) @ 2000 | Carter WCD 548 (2) | |
| 1947 | Streamliner (8 MB)[9] | 248.9 (4.1) | 107.00 (78.74) @ 3700 | 190.00 (257.64) @ 2000 | Carter WCD 630 (2) | |
| 1948 | Silver Streak Wagon[10] | 248.9 (4.1) | 108.00 (79.5) @ 3700 | NA (NA) @ 2000 | Carter WCD 630 (2) | |
| 1948 | Torpedo (8PA)[11] | 248.9 (4.1) | 107.00 (78.74) @ 3700 | 190.00 (257.64) @ 2000 | Carter WCD 652 (2) | |
| 1949 | Chieftain (8R)[12] | 248.9 (4.1) | 106.00 (78.00) @ 3800 | 190.00 (257.64) @ 2200 | Carter WCD 719/720(2) |
[edit] 1950-1954 - 268 in³
| Year | Model name (number) | Displacement in³ ( L) | Output bhp (kW) @ RPM | Torque ft·lbf (Nm) @ RPM | Carburetor series (bbl) | |
| 1950 | Silver Streak 8 (50-27) | 268.2 (4.4) | 108 (79.48) @ 3600 | 208 (282.04) @ 1800 | Carter WCD 719/720 (2) | [4] |
| 1951 | Silver Streak 8 (51-27) | 268.2 (4.4) | 116 (85.37) @ 3600 | 220 (298.32) @ 2000 | Carter WCD 719/720 (2) | [4] |
| 1952 | Silver Streak 8 W/Syncromesh (52-27) | 268.2 (4.4) | 118 (86.85) @ 3600 | 222 (301.03) @ 2200 | Carter WCD 719/720 (2) (6.8-1 compression) | [4] |
| 1952 | Silver Streak 8 W/Hydra-Matic (52-27) | 268.2 (4.4) | 122 (89.79) @ 3600 | 222 (301.03) @ 2200 | Carter WCD 719/720 (2) (7.7-1 compression) | [4] |
| 1953 | Chieftan 8 W/Syncromesh (53-27) | 268.2 (4.4) | 118.00 (86.85) @ 3600 | 222 (301.03) @ 2200 | Carter WCD 2010S (2) (6.8-1 compression) | [4] |
| 1953 | Chieftan 8 W/Hydra-Matic (53-27) | 268.2 (4.4) | 122.00 (89.79) @ 3600 | 222 (301.03) @ 2200 | Carter WCD 2010S (2) (7.7-1 compression) | [4] |
| 1954 | Chieftan 8 W/Syncromesh (54-27) | 268.2 (4.4) | 122 (89.79) @ 3800 | 222 (301.03) @ 2200 | Carter WCD? (2) (6.8-1 compression) | [13] |
| 1954 | Chieftan 8 W/Hydramatic (54-27) | 268.2 (4.4) | 127 (93.47) @ 3800 | 234 (317.30) @ 2200 | Carter WCD? (2) (7.7-1 compression) | [13] |
[edit] "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 230 bhp, though some[14] estimated it at over 300 bhp. 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.[15]
| Year | Model name (number) | Displacement in³ ( L) | Output bhp (kW) @ RPM | Torque ft·lbf (Nm) @ RPM | Carburetor series (bbl) |
| 1954 | (SO 2026) [16] | 268 (4.4) | 230.00 (169.28) @ 3700 | NA (NA) @ 2000.00 | Carter YH 2206[17] (1) x 4 |
[edit] Footnotes
- ^ Silver-Streak: The name taken from a body detail peculiar 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.
- ^ Motor Trend Magazine, February 1965, available online
- ^ a b Pontiac sales brochure, Pontiac Motor Division, 1933.
- ^ a b c d e f g h i j k l m Motor's Auto Repair Manual,Sixteenth Edition, Motor.,1953.
- ^ Second Chance Garage A web based, statistical database for mid-century Pontiacs
- ^ Concept Carz Valuable online, statistical database for most classic cars
- ^ Concept Carz
- ^ Second Chance Garage
- ^ Second Chance Garage
- ^ Concept Carz
- ^ Second Chance Garage
- ^ Second Chance Garage
- ^ a b Motor's Auto Repair Manual, Motor.,1963
- ^ "300 bhp, as estimated by Special owner and concept collector/restorer Joseph Bortz, in a filmed interview viewable at Motor Trend Magazine, available online.
- ^ "Why the Straight-8?, explained in the same interview above.
- ^ Concept Carz
- ^ Chevrolet carburetors
