Pontiac straight-8 engine
The Pontiac straight-8 engine is an inline eight-cylinder automobile engine produced by Pontiac 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 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 It was superseded by Pontiac's new V8, the 287, in 1955.
| Pontiac straight-8 engine | |
|---|---|
 | |
| Overview | |
| Manufacturer | General Motors |
| Also called | Silver Streak |
| Production | 1933–1954 |
| Layout | |
| Configuration | Naturally aspirated Straight-8 cylinder |
| Displacement |
|
| Block material | Cast iron |
| Head material | Cast iron |
| Valvetrain | Flathead |
| Compression ratio | 5.7:1, 6.8:1, 7.7:1 |
| Combustion | |
| Fuel system | Carter Carburetor |
| Fuel type | Gasoline |
| Oil system | Full pressure |
| Cooling system | Water-cooled |
| Output | |
| Power output | 77–252 bhp (57–188 kW) |
| Torque output | 153–234 lb⋅ft (207–317 N⋅m) |
| Chronology | |
| Predecessor | 251 cu in (4.1 L) flathead I8 |
| Successor | 287 cu in (4.7 L) OHV V8 |
History
The straight-8 was dubbed the Silver-Streak[1] at Pontiac Division. Powered by the "eight", a Pontiac was promoted as a likable automobile, with 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. Interesting to note that the Strato Streak V-8 was ready to go in 1953, but was held back by the protesting Buick and Olds divisions. Evidence of this is in the details of the chassis/steering of 1953 and 1954 Pontiac's which were designed for the V-8. The V8 configuration of the "Strato-Streak" 287-cubic-inch (4.7 L) 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 (fall of 1956), under the guidance of Bunkie Knudsen Pontiac was determined to change its image into a performance car to boost sales, this led Knudsen to look for further talent, including Pete Estes as chief engineer (taken from Olds division) and John DeLorean as director of advanced engineering, a former Packard and Chrysler engineer. 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.
Market
Designed and priced for conservative lower middle class buyers, the Pontiacs filled a slot between the popular Chevrolet and the higher priced Oldsmobiles and Buicks.
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 (one- or two-barrel) downdraft carburetor.
Advantages
Of all cylinder layouts without balance shaft a straight eight design has very low inherent vibration, while the side-valve layout contains the moving parts of the valve train within the cast-iron block, enabling it to be very quiet compared to an overhead valve configuration (as in the contemporary Buick engines). Combined with a substantial exhaust manifold and effective intake and exhaust muffling this can lead to a very quiet vehicle, both internally and externally. At the time of its use a quiet engine was thought to be a mark of quality in an automobile. Bores need be of small diameter to keep the engine length down and so strokes must be long to obtain larger displacements - such configurations (called "undersquare") exhibit good low-rpm torque and are capable of slow idle speeds, enhancing both drivability and quietness. While Chrysler vehicles had similar engines they were not targeted for the lower middle price range enabled by General Motors' manufacturing expertise and volumes of the time.
Disadvantages
As with other iron block straight configurations the engine is considerably heavier than an equivalent V configuration, requiring more materials for the crank and crankcase and so increasing overall vehicle weight in even greater proportion. The long crankshaft tends to exhibit torsional vibration modes under high power, while side-valve flathead engines inhibit smooth intake and exhaust gas flow, limiting power. None of these disadvantages were disabling until the "horsepower race" initiated in the early 1950s ensured the dominance of the overhead valve V8.
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,[2] and was increased to 6.2:1 ratio in 1934.[3] In 1940 it was increased again to 6.5:1. From 1952 to 1954 two compression ratios were specified, 6.8:1 with syncromesh (manual) transmission, and 7.7:1 ratio with Hydramatic automatic transmission.[4] The engine had a remarkably low idle speed of a 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 and full bearing inserts, unlike its Chevrolet cousin.
Below are specifications as per the model year and displacement, with output shown as horsepower (kilowatts).
| Year | Model name (number) | Displacement | Power output | Torque | Carburetor series (bbl) | |
| 1933 | Eight | 223.4 cu in (3.7 L) | 77 hp (57 kW) @ 3600 rpm[2] | N/A | Carter W-1 (1) | |
| 1934 | 84 hp (63 kW) @ 3600 rpm | 153 lb⋅ft (207 N⋅m) @ 1600 rpm[3] | Carter W-1 (1) Model 283-S[3] | |||
| 1935 | 84 hp (63 kW) @ 3800 rpm | Carter W-1 (1) | [4] | |||
| 1936 | 232.3 cu in (3.8 L) | 87 hp (65 kW) @ 3800 rpm | 161 lb⋅ft (218 N⋅m) @ 1600 rpm | [4] | ||
| 1937 | 248.9 cu in (4.1 L) | 100 hp (75 kW) @ 3800 rpm | 172 lb⋅ft (233 N⋅m) @ 1600 rpm | [4] | ||
| 1938 | 100 hp (75 kW) @ 3700 rpm | [4] | ||||
| 1939 | De Luxe 8 | [4] | ||||
| 1940 | Deluxe[6] | 175 lb⋅ft (237 N⋅m) @ 1600 rpm | Carter WA-1, WD-0 (2) | |||
| 1941 | Custom & Torpedo Streamliner 8 | 103 hp (77 kW) @ 3500 rpm | 190 lb⋅ft (258 N⋅m) @ 2200 rpm | Carter WD-O (2) | [4] | |
| 1942 | Streamliner[7] | 103 hp (77 kW) @ 3700 rpm | NA @ 2000 | Carter WD-0 (2) | ||
| 1946 | Torpedo (27LA78)[8] | 107 hp (80 kW) @ 3700 rpm | 190 lb⋅ft (258 N⋅m) @ 2000 rpm | Carter WCD 548 (2) | ||
| 1947 | Streamliner (8 MB)[9] | Carter WCD 630 (2) | ||||
| 1948 | Streamliner Wagon (28)[10] | 108 hp (81 kW) @ 3700 rpm | NA @ 2000 | |||
| Torpedo (8PA)[11] | 107 hp (80 kW) @ 3700 rpm | 190 lb⋅ft (258 N⋅m) @ 2000 rpm | Carter WCD 652 (2) | |||
| 1949 | Chieftain (8R)[12] | 106 hp (79 kW) @ 3800 rpm | 190 lb⋅ft (258 N⋅m) @ 2200 rpm | Carter WCD 719/720 (2) | ||
| 1950 | Silver Streak 8 (50-27) | 268.2 cu in (4.4 L) | 108 hp (81 kW) @ 3600 rpm | 208 lb⋅ft (282 N⋅m) @ 1800 rpm | [4] | |
| 1951 | Silver Streak 8 (51-27) | 116 hp (87 kW) @ 3600 rpm | 220 lb⋅ft (298 N⋅m) @ 2000 rpm | [4] | ||
| 1952 | Silver Streak 8 W/Syncromesh (52-27) | 252 hp (188 kW) (modified) @ 3600 rpm | 222 lb⋅ft (301 N⋅m) @ 2200 rpm | Carter WCD 719/720 (2) (6.8:1 compression) | [4] | |
| Silver Streak 8 W/Hydra-Matic (52-27) | 122 hp (91 kW) @ 3600 rpm | 222 lb⋅ft (301 N⋅m) @ 2200 rpm | Carter WCD 719/720 (2) (7.7:1 compression) | [4] | ||
| 1953 | Chieftain 8 W/Syncromesh (53-27) | 118 hp (88 kW) @ 3600 rpm | Carter WCD 2010S (2) (6.8:1 compression) | [4] | ||
| Chieftain 8 W/Hydra-Matic (53-27) | 122 hp (91 kW) @ 3600 rpm | Carter WCD 2010S (2) (7.7:1 compression) | [4] | |||
| 1954 | Chieftain 8 W/Syncromesh (54-27) | 122 hp (91 kW) @ 3800 rpm | Carter WCD? (2) (6.8:1 compression) | [13] | ||
| Chieftain 8 W/Hydramatic (54-27) | 127 hp (95 kW) @ 3800 rpm | 234 lb⋅ft (317 N⋅m) @ 2200 rpm | Carter WCD 2122S (2) (7.7:1 compression) | [13] | ||
"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 high output 268-cubic-inch (4.4 L) 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, modified with a high-lift cam and fitted with four Carter YH side-draft one-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 (172 kW), though some estimated it at over 300 bhp (224 kW).[14] Like the Special, only two 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-eight be used to keep the V8 a secret from consumers for one more year until its debut the following year.[15]
| Year | Model name (number) | Displacement | Power Output | Torque | Carburetor series (bbl) |
| 1954 | (SO 2026) [16] | 268 cu in (4.4 L) | 230 hp (172 kW) @ 3700 rpm | NA @ 2000 rpm | Carter YH 2206[17] (1) x 4 |
Footnotes
- 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.
- Pontiac sales brochure, Pontiac Motor Division, 1933.
- Pontiac Shop Manual 1934 Models General Motors of Canada
- 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
- "1942 Pontiac Streamliner (Series 26, Series 28, KB Line, Six, Eight) - conceptcarz.com". Retrieved 23 March 2017.
- "1946 Pontiac 249 Inline 8 Engine Specs". Retrieved 23 March 2017.
- "1947 Pontiac 249 Inline 8 Engine Specs". Retrieved 23 March 2017.
- "1948 Pontiac Silver Streak (Torpedo, Series 25 (Six), Series 27 (Eight)) - conceptcarz.com". Retrieved 23 March 2017.
- "1948 Pontiac 249 Inline 8 Engine Specs". Retrieved 23 March 2017.
- "1949 Pontiac 249 Inline 8 Engine Specs". Retrieved 23 March 2017.
- Motor's Auto Repair Manual, Motor.,1963
- Such as Special owner and concept collector/restorer Joseph Bortz, in a filmed interview viewable at Motor Trend Magazine, available online Archived 2006-06-17 at the Wayback Machine.
- "Why the Straight-8?, explained in the same interview above.
- "1954 Pontiac Bonneville Special Motorama - conceptcarz.com". Retrieved 23 March 2017.
- "THE CARBURETOR SHOP / Chevrolet 1912 - 1959". Retrieved 23 March 2017.