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

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 It was superseded by Pontiac's new V8, the 287 OHC, in 1955.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