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CATEGORIES (articles) > Engines > Pontiac > Pontiac straight 8

Pontiac straight 8


Pontiac straight-8 engine
Also called: Silver Streak
Manufacturer: General Motors
Production: 1935 to 1954
Predecessor: 251  in³ flathead V8
Successor: 287  in³ OHV V8
A straight-8 in a 1950 Pontiac Streamliner

The straight-8 was an eight-cylinder, in-line automobile engine that was used in production Pontiacs from 1935 to 1954. Introduced in 1933, 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 It was superseded by Pontiac's new V8, the 287 OHC, in 1955.

History

The straight-8 was dubbed the Silver-Streak 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. Powered by the "eight", a Pontiac was widely regarded as a likable and highly reliable automobile, with enough power under the hood to get the job done in affordable luxury. It was a quiet, smooth running engine that served the needs of the American consumer adequately.

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 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).

Specifications

Compression on the "eight" was at 6.5 - 1 ratio up to 1952, then 6.8-1, and 7.7-1 ratio to '54, with an engine idle speed of a remarkably low 450 rpm with standard transmission and 375 rpm (while in drive) for the automatic. 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.

Below are specifications as per the model year and displacement.

1935-1937 - 223 in³

Year Model name (number) Displacement  in³ ( L) Output bhp (kW) @ RPM Torque ft·lbf (Nm) @ RPM Carburetor series (bbl)
1936 Silver Streak 223 (3.6) 85.00 (62.56) @ 3520 160.00 (216.96 ) @ 1600 Carter W1 (1)

1938-1949 - 249 in³

Year Model name (number) Displacement  in³ ( L) Output bhp (kW) @ RPM Torque ft·lbf (Nm) @ RPM Carburetor series (bbl)
1940 Deluxe 248.9 (4.1) 100.00 (73.6) @ 3700 175.00 (237.3) @ 1600.00 Carter WA-1, WD-0 (2)
1942 Streamliner 248.9 (4.1) 103.00 (75.8) @ 3700 NA (NA) @ 2000 Carter WD-0 (2)
1946 Torpedo (27LA78) 248.9 (4.1) 107.00 (78.74) @ 3700 190.00 (257.64) @ 2000 Carter WCD 548 (2)
1947 Streamliner (8 MB) 248.9 (4.1) 107.00 (78.74) @ 3700 190.00 (257.64) @ 2000 Carter WCD 630 (2)
1948 Silver Streak Wagon 248.9 (4.1) 108.00 (79.5) @ 3700 NA (NA) @ 2000 Carter WCD 630 (2)
1948 Torpedo (8PA) 248.9 (4.1) 107.00 (78.74) @ 3700 190.00 (257.64) @ 2000 Carter WCD 652 (2)
1949 Chieftain (8R) 248.9 (4.1) 106.00 (78.00) @ 3800 190.00 (257.64) @ 2200 Carter WCD 719/720(2)

1950-1954 - 268 in³

Year Model name (number) Displacement  in³ ( L) Output bhp (kW) @ RPM Torque ft·lbf (Nm) @ RPM Carburetor series (bbl)
1950 Streamliner (8T) 268 (4.4) 108.00 (79.48) @ 3600 208.00 (282.04) @ 1800 Carter WCD 719/720 (2) m (6.5-1 compression)
1951 Chieftain (8U) with Hydromatic trans 268 (4.4) 116.00 @ 3600 220.00 @ 2000 Carter WCD 719/720 (2) (6.5-1 compression)
1953 Parisienne (SO 1759) 268 (4.4) 122.00 (89.79) @ 3600 227 @ 2200 Carter WCD 2283 (2) (7.7-1 compression)
1954 Chieftain (8U) 268 (4.4) 127.00 @ 3800 234.00 @ 2200 Carter WCD 719/720? (2) (7.7-1 compression)

"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 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.

Year Model name (number) Displacement  in³ ( L) Output bhp (kW) @ RPM Torque ft·lbf (Nm) @ RPM Carburetor series (bbl)
1954 (SO 2026) 268 (4.4) 230.00 (169.28) @ 3700 NA (NA) @ 2000.00 Carter YH 2206 (1) x 4

Footnotes

  1. ^ 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.
  2. ^ Motor Trend Magazine, February 1965, available online
  3. ^ Second Chance Garage A web based, statistical database for mid-century Pontiacs
  4. ^ Pontiac carburetors - applications and repair kits
  5. ^ Concept Carz Valuable online, statistical database for most classic cars
  6. ^ Concept Carz
  7. ^ Second Chance Garage
  8. ^ Second Chance Garage
  9. ^ Concept Carz
  10. ^ Second Chance Garage
  11. ^ Second Chance Garage
  12. ^ Second Chance Garage
  13. ^ Second Chance Garage
  14. ^ The Parisienne was a one of a kind concept car introduced at the 1953 Motorama. It had a unique straight-8 of higher performance.
  15. ^ Second Chance Garage
  16. ^ "300 bhp, as estimated by Special owner and concept collector/restorer Joseph Bortz, in a filmed interview viewable at Motor Trend Magazine, available online.
  17. ^ "Why the Straight-8?, explained in the same interview above.
  18. ^ Concept Carz
  19. ^ Chevrolet carburetors




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