1955-1982 Pontiac V-8s - Part 4 - Over-Drive Magazine

Pontiac Large Crankshaft Journal (3.25″) V8s

Pontiac V8 engines are broken into two categories, small main journal and large main journal engines. All Pontiac engines have the same deck height except for the 1969 303 Trans Am engine and the short-lived 301 and 265 V8s of the early 80s. The early 287-370 engines used smaller main journals, with the first two utilizing 2.5″ mains and the 347 and 370 using 2.623″ mains. The 301 and 265 reverted to the original 287’s 2.5″ mains. All 389 and 400 inch engines used “small” main journals which were 3.00″. The large main journal engines are listed here:

- 421 CID 1961-1966
- 428 CID 1967-1969
- 455 CID 1970-1976

Engines are listed in the order of introduction.

421 CID V8 (1961-1966)

Introduced in 1961 as a dealer installed Super Duty option (to bonafide racers), the 421 cu. in. V8 was the 389 design bored to 4.09375″ and stroked to 4.00″ for 421.2 cu. in. Its primary difference was larger, 3.25″ main journals and 4-bolt 2-4 main journal caps. Unlike previous displacement increases of Pontiac V8 engine, it did not replace the 389. The Super Duty versions were extensively used in NASCAR stock car racing and drag racing competition.

The 421 also marked the end of the option for a forged steel crankshaft, which was replaced by an “Armasteel” cast nodular iron crankshaft. This became the standard crankshaft of the entire Pontiac V-8 line until ’67. “Armasteel” was no more than a fancy name for a hardened cast iron unit. In 1967, with advent of the 428, Pontiac went to the common “Nodular Cast Iron” name for this crankshaft, which they used until 1975.

The blocks were cast with the provision for 4-bolt mains at positions 2-4 and all large journal engines have this provision, though many “HO” versions are not fitted with 4-bolt caps.

1961

In 1961 the 421 was only offered with dual four barrel carburetors, and was rated @ 373 HP with the two-4-barrel combination.

1961 Pontiac 421 CID Engine Specifications
Click the tabs for specific engine information

1961 421 CID 373-405 HP

Optional Dealer Installed “Super Duty” V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 11.0:1. Horsepower: (early) 373 @ 5400 RPM (late) 405 @ 5600 RPM. Torque: 430 @ 4400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 283°, Exhaust 293°, Overlap 60°, Lift 0.411″. Carburetors: two 4-barrel Carter AFB carburetors (front) 3435, (rear) 3433. Low-restriction dual exhausts and dual-breaker ignition.

1962

The 421 Super Duty V8 became factory installed in 1962. It was still primarily a professional racer’s unit with a 2 4-barrel Super Duty engine rated at 405 HP (racer’s engine) and a “standard” 421, still equipped with 2 4-barrels, rated at a paltry 320 HP.

1962 Pontiac 421 CID Engine Specifications
Click the tabs for specific engine information

Catalina, Star Chief, Bonneville & Grand Prix 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 320 @ 4800 RPM. Torque: 455 @ 4400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 283°, Exhaust 293°, Overlap 60°, Lift 0.411″. Carburetor: 4-barrel Rochester Model 3300S.

Optional “421 Super Duty” V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 11.0:1. Horsepower: 405 @ 5600 RPM. Torque: 430 @ 4400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 283°, Exhaust 293°, Overlap 60°, Lift 0.411″. Carburetors: two 4-barrel Carter AFB carburetors Model (front) 3433 (rear) 3435. Low-restriction dual exhausts and dual-breaker ignition.

1963

In 1963 a street version became available from the factory with a four barrel or Tri-Power carburetion. These engines were called “HO” for High Output” and did not receive the 4-bolt main caps of the Super Duty. It was offered as a 4-barrel or 3 2-barrel engine. The pedestrian 4-barrel was rated at 320 HP and was installed in the big cars as a step up from the 389, the HO 4-barrel was rated at 353 HP and the 3 2-barrel HO version was rated at 370 HP.

The Super Duty engine came in three flavors: 4-barrel rated at 390 HP and the 2 4-barrel engine which was either 405 or 410 HP depending on the camshaft. All 389 SD engines were dropped.

1963 Pontiac 421 CID Engine Specifications
Click the tabs for specific engine information

Catalina, Star Chief, Bonneville & Grand Prix HO 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 353 @ 5000 RPM. Torque: 455 @ 3400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 292°, Exhaust 302°, Overlap 65°, Lift 0.400″. Carburetor: 4-barrel Rochester Model 3574S (synchromesh), 3545S (automatic).

Catalina, Star Chief, Bonneville & Grand Prix HO 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 353 @ 5000 RPM. Torque: 455 @ 3400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 292°, Exhaust 302°, Overlap 65°, Lift 0.400″. Carburetors: three 2-barrel Rochester carburetors: (front) 7013078 (center Syncromesh) 7023161 (center Hydra-matic) 7023162, (rear) 7013079.

Super Duty 421 CID V-8 option in Catalina two-door only: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 11.00:1. Horsepower: 390 @ 5800 RPM. Torque: 435 @ 4400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft type: Hydraulic flat-tappet McKellar #10 Duration: 308/320° intake/exhaust, Overlap 87°, Lift: 0.445/0.447″ intake/exhaust. Valve train: 1.65:1-ratio rocker arms. Carburetor Carter AFB 3475S.

NOTE: various camshafts were used in this engine – we have cited the Popular McKellar #10 here.

Super Duty 421 CID V-8 option in Catalina two-door only: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 11.00:1. Horsepower: 405 @ 5600 RPM. Torque: 425 @ 4400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft type: Hydraulic flat-tappet McKellar #10 Duration: 308/320° intake/exhaust, Overlap 87°, Lift: 0.445/0.447″ intake/exhaust. Valve train: 1.65:1-ratio rocker arms. Carburetor Carter AFB 3433S (Front) 435S (Rear).

NOTE: various camshafts were used in this engine – we have cited the Popular McKellar #10 here.

Super Duty 421 CID V-8 option in Catalina two-door only: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 12.00:1. Horsepower: 410 @ 5800 RPM. Torque: 430 @ 4600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft type: Hydraulic flat-tappet McKellar #10 Duration: 308/320° intake/exhaust, Overlap 87°, Lift: 0.445/0.447″ intake/exhaust. Valve train: 1.65:1-ratio rocker arms. Carburetor Carter AFB 3433S (Front) 435S (Rear).

NOTE: various camshafts were used in this engine – we have cited the Popular McKellar #10 here.

1964

By 1964, the SD Pontiacs were no more. 421s could be retrofitted with the 4-bolt main caps and the 1962-63 intakes and go racing, but only in NASCAR. By this time lighter cars were prevailing in the stock ranks and the AFX rank cars were all manufactured by privateers and dealerships, so there was no need to deliver these loss-leader cars. Now the 421 came in only three versions, once again the 4-barrel 320 HP big car mover, and a 350 HP 3 2-barrel performance version. The SD engines were gone, now replaced by the HO version with 3 2-barrels and a tougher cam for 370 HP.

1964 Pontiac 421 CID Engine Specifications
Click the tabs for specific engine information

Catalina, Star Chief, Bonneville & Grand Prix 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 320 @ 4400 RPM. Torque: 455 @ 2800 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.409″ Exhaust 0.411″. Carburetor: 4-barrel Rochester Model AFB 3650S (synchromesh), 3651S (automatic).

Catalina, Star Chief, Bonneville & Grand Prix 350 HP 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 353 @ 5000 RPM. Torque: 455 @ 3400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.409″ Exhaust 0.411″. Carburetors: three 2-barrel Rochester carburetors: (front) 7023078 (center syncromesh) 7023161 (center Hydra-matic) 7023162, (rear) 7023079.

Catalina, Star Chief, Bonneville & Grand Prix HO 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 370 @ 5200 RPM. Torque: 460 @ 3800 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.415″ Exhaust 0.412:. Carburetors: three 2-barrel Rochester carburetors: (front) 7013078 (center synchromesh) 7023161 (center Hydra-matic) 7023162, (rear) 7013079.

1965

The entry level big car mover 4-barrel got last year’s 350 HP cam and moved up to 338 HP. The auto trans HO three 2-barrel got tweaked timing and moved up to 356 HP, and the big brother stick car was up to 376 HP.

1965 Pontiac 421 CID Engine Specifications
Click the tabs for specific engine information

Catalina, Star Chief, Bonneville & Grand Prix 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.5:1. Horsepower: 338 @ 4600 RPM. Torque: 433 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.409″ Exhaust 0.411″. Carburetor: 4-barrel Rochester Model AFB 3895S (synchromesh), 3898S (automatic).

Catalina, Star Chief, Bonneville & Grand Prix 356 HP HO 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 356 @ 4800 RPM. Torque: 459 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.409″ Exhaust 0.410″. Carburetors: three 2-barrel Rochester carburetors: (front) 7024078 (center synchromesh) 7025075 (center Hydra-matic) 7025074, (rear) 7025079.

Catalina, Star Chief, Bonneville & Grand Prix 376 HP HO 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 376 @ 5000 RPM. Torque: 461 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.415″ Exhaust 0.412:. Carburetors: three 2-barrel Rochester carburetors: (front) 7024078 (center synchromesh) 7025075 (center Hydra-matic) 7025074, (rear) 7025079.

1966

In 1966 a 350 HP 4-barrel engine was considered between the 338 and the HO engines, but not adopted. As in 1965, the auto trans HO 3 2-barrel got tweaked timing and moved up to 356 HP, and the big brother stick car was still at 376 HP.

1966 Pontiac 421 CID Engine Specifications
Click the tabs for specific engine information

Catalina, Star Chief, Bonneville & Grand Prix 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.5:1. Horsepower: 338 @ 4600 RPM. Torque: 433 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.409″ Exhaust 0.411″. Carburetor: 4-barrel Carter Model AFB 4033S (synchromesh), 4037S (automatic).

Catalina, Star Chief, Bonneville & Grand Prix 356 HP HO 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 356 @ 4800 RPM. Torque: 459 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.409″ Exhaust 0.410″. Carburetors: three 2-barrel Rochester carburetors: (front synchromesh) 7025078 (front Hydra-matic) 7024078 (center synchromesh) 7026075 (center Hydra-matic) 7026074, (rear synchromesh) 7025079 (rear Hydra-matic) 7024079.

Catalina, Star Chief, Bonneville & Grand Prix 376 HP HO 421 V-8: Overhead valves. Cast iron block. Displacement: 421 CID. Bore and stroke: 4.09375 x 4.00″. Compression ratio: 10.75:1. Horsepower: 376 @ 5000 RPM. Torque: 461 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.415″ Exhaust 0.412:. Carburetors: three 2-barrel Rochester carburetors: (front) 7024078 (center synchromesh) 7025075 (center Hydra-matic) 7025074, (rear) 7025079.

428 CID V8 (1967-1969)

In 1967 the 421 was bored to 4.125″ with the same stroke as the 421 at 4.00″, increasing its displacement to 427.6 cu in. The crankshaft in the 428 was identified as Nodular Iron by a “N” cast on it as opposed to the 421’s Armasteel designation. The Three 2-barrel option was dropped per GM’s ruling that only the Corvette could carry this configuration.

1967

This engine produced 360 HP in standard 4-barrel form and 376 HP in 4-barrel HO form.

1967 Pontiac 428 CID Engine Specifications
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Full Size 360 HP 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.5:1. Horsepower: 360 @ 4600 RPM. Torque: 472 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Carter Model AFB 4243S or Rochester 7027263.

Full Size 360 HP 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.5:1. Horsepower: 360 @ 4600 RPM. Torque: 472 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Carter Model AFB 4242S or Rochester 7027262.

Full Size 376 HP HO 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.75:1. Horsepower: 376 @ 5100 RPM. Torque: 462 @ 3400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.409″ Exhaust 0.410″. Carburetor: 4-barrel Carter Model AFB 4243S or Rochester 7027263.

1968

Only 2 different 4-barrel engines were offered, however the horsepower ratings were raised to 375 and 390, with the 390 the HO engine.

1968 Pontiac 428 CID Engine Specifications
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Full Size 375 HP 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.5:1. Horsepower: 375 @ 4800 RPM. Torque: 472 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel C Rochester 7028263.

Full Size 375 HP 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.5:1. Horsepower: 375 @ 4800 RPM. Torque: 472 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: Rochester 7028268.

Full Size 390 HP HO 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.75:1. Horsepower: 390 @ 5200 RPM. Torque: 462 @ 3400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.413″ Exhaust 0.414″. Carburetor: 4-barrel Rochester Model 7028267.

Full Size 390 HP HO 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.75:1. Horsepower: 390 @ 5200 RPM. Torque: 465 @ 3400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester Model 7028268.

1969

In 1969, Pontiac issued a revised crankshaft made from Pearlite malleable iron, although it still used the” N” casting designation. This new material had better alloys in the iron. The non-HO engine returned to 360 HP and the HO engine remained at 390 HP.

1969 Pontiac 428 CID Engine Specifications
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Full Size 360 HP 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.5:1. Horsepower: 360 @ 4600 RPM. Torque: 472 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester 7029263.

Full Size 360 HP 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.5:1. Horsepower: 360 @ 4600 RPM. Torque: 472 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: Rochester 7029268.

Full Size 390 HP HO 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.75:1. Horsepower: 390 @ 5200 RPM. Torque: 465 @ 3400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.413″ Exhaust 0.414″. Carburetor: 4-barrel Rochester Model 7029263.

Full Size 390 HP HO 428 V-8: Overhead valves. Cast iron block. Displacement: 428 CID. Bore and stroke: 4.125 x 4.00″. Compression ratio: 10.75:1. Horsepower: 390 @ 5200 RPM. Torque: 465 @ 3400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester Model 7029268.

455 CID V8 (1970-1976)

For 1970, the 428 bore was expanded to 4.155″, combined with a 4.21875″ stroke, yielding a total displacement of 457.6 cu in. and bringing it in line with the Oldsmobile and Buick V8s of 455 cu. in. The engine was available on all full-size Pontiacs, the Grand Prix and as the 455 HO in the Pontiac GTO, as GM had lifted its restrictions on the use of engines larger than 400 cubic inches in mid-sized cars.

The 455 was used through 1976. The 455, was “under square” – with a longer stroke relative to bore, emphasized torque over hp, and though advertised as less powerful than some high-performance iterations of the 400, it had a torque rating of 500 ft lbs, which was 55 more ft lbs. of torque than the 1970 performance 400’s offered in the GTO and Firebird.

1970

The 1970 455 came in only two flavors, and was used across the board. Though powerful, Pontiac had placed its performance marbles in the hands of the old 400, where the Ram Air III and IV were the true hot motors. Thus while there was a 360 and 370 HP versions, they were not as hefty as their 400 inch counterparts.

1970 Pontiac 455 CID Engine Specifications
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Full Size 360 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 10.25:1. Horsepower: 360 @ 4600 RPM. Torque: 500 @ 3100 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.414″ Exhaust 0.413″. Carburetor: 4-barrel Rochester 7040267.

Full Size 360 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 10.25:1. Horsepower: 360 @ 4600 RPM. Torque: 500 @ 3100 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester 7040268.

1971

The tables were turned in 1971 when the lowered compression killed off the RAM Air 400 CID cars. The 455, however, came in 280, 325 and 335 HO versions.

The 335 HP HO was a true performance engine, even including the 4-bolt mains and a reinforced block, and improved cylinder head design with 0.125″ inch taller intake ports and special round exhaust ports for better breathing, making some 335 hp (310 SAE Net). This was an extremely rare engine that was standard in the Firebird Trans Am.

1971 Pontiac 455 CID Engine Specifications
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Full Size Except Grand Prix – L66 280 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.2:1. Horsepower: 280 @ 4400 RPM. Torque: 455 @ 2000 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 2-barrel Rochester 7041064.

NOTE: Not available on LeMans, GTO or Firebird.

All Series – L75 325 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.2:1. Horsepower: 325 @ 4400 RPM. Torque: 455 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Rochester 7041262.

LeMans, Firebird and GTO only Hydra-matic Transmission LS5 – 335 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 335 @ 4800 RPM. Torque: 480 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester 7041268.

LeMans, Firebird and GTO only Manual Transmission LS5 – 335 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 335 @ 4800 RPM. Torque: 480 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester 7041267.

LeMans, Firebird and GTO only Hydra-matic Transmission – LS5 – 335 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 335 @ 4800 RPM. Torque: 480 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester 7041270.

LeMans, Firebird and GTO only Manual Transmission LS5 – 335 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 335 @ 4800 RPM. Torque: 480 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester 7041273.

1972

This year was a real retrenchment for Pontiac, with two 455s offered. The base 455 was replaced with a 4-barrel 400 in all but the full-size (except Grand Prix), leaving only the 250 HP and 300 HP versions of the 455 for the rest of the line.

1972 Pontiac 455 CID Engine Specifications
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Full-Size Except Grand Prix L66 185/200 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.2:1. Horsepower: (single exhaust) 185 @ 4000 RPM; (dual exhaust) 200 @ 4000. Torque: (single exhaust) 350 @ 2000 RPM; 370 @ 2000 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Rochester 7042262.

All Series Except Ventura and Firebird – L75 250 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.2:1. Horsepower: 250 @ 3600 RPM. Torque: 375 @ 2400 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Rochester 7042262.

LeMans, Firebird and GTO only Hydra-matic Transmission LS5 – 300 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 300 @ 4000 RPM. Torque: 415 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester 7042270.

LeMans, Firebird and GTO only Hydra-matic Transmission LS5 – 300 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 300 @ 4000 RPM. Torque: 415 @ 3200 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″. Carburetor: 4-barrel Rochester 7042273.

1973

In 1973, a further refined and even stronger version, called the Super Duty (SD) engine was introduced with “only” 310 HP SAE net, using a similar camshaft specifications to the old 1970 Ram Air IV 400. This 455 SD used round port cylinder heads similar to those used on the 1971 455 HO, with specific “LS2″ intake and cast iron exhaust header-manifolds. It was considered the most powerful factory installed V8 engine offered that year. In addition to the more refined cylinder heads, there were block casting reinforcements in the lifter galley and in the main bearing oil pan rail area along with the addition of forged connecting rods with larger 7/16” diameter bolts.

Further, the SD was cast with a provision for dry sump oiling from the factory. This truly was a racing engine, de-tuned for use in passenger cars. It was offered in the Firebird from mid-1973 and 1974, after which point it was discontinued. Another pedestrian 455 was also available in all other Pontiacs, rated at 250 HP.

1973 Pontiac 455 CID Engine Specifications
Click the tabs for specific engine information

Full-Size Except Grand Prix 200 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.0:1. Horsepower: 200 @ 3800. Torque: 350 @ 2000 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Rochester 7043262.

All Series Except Ventura – L75 250 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.2:1. Horsepower: 250 @ 4000 RPM. Torque: 370 @ 2800 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Rochester 7043262.

Firebird Only Manual Transmission – L75 250 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.2:1. Horsepower: 250 @ 4000 RPM. Torque: 370 @ 2800 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Rochester 7043265.

Mid-Size (All), Grand Prix and Firebird Only, Hydra-matic Transmission – Super Duty 310 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 310 @ 4000 RPM. Torque: 390 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 308°, Exhaust 320°, Overlap 87°, Lift: Intake 0.470″ Exhaust 0.470″. Carburetor: 4-barrel Rochester 7043270.

NOTE: The Super Duty AMT was listed as available for the Grand Prix, and the entire mid-size line, however, few if any were fitted.

Firebird and Mid-Size Coupe Only, Manual Transmission – Super Duty 310 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 310 @ 4000 RPM. Torque: 390 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 308°, Exhaust 320°, Overlap 87°, Lift: Intake 0.470″ Exhaust 0.470″. Carburetor: 4-barrel Rochester 7043273.

NOTE: The Super Duty AMT was listed as available for the entire mid-size line coupe, however, few if any were fitted.

1974

In 1974, the Super Duty (SD) engine continued albeit re-rated to 290 HP SAE net, using a similar but different camshaft specification from the previous year. The 455 SD used round port cylinder heads similar to those used on the 1971 455 HO, with specific “LS2″ intake and cast iron exhaust header-manifolds. It was still considered the most powerful factory installed V8 engine offered that year. There were block casting reinforcements in the lifter galley and in the main bearing oil pan rail area along with the addition of forged connecting rods with larger 7/16” diameter bolts. After 1974 it was discontinued.

The pedestrian 455 was also available in all Pontiacs except Ventura, rated at 250 HP, with auto transmission only.

1974 Pontiac 455 CID Engine Specifications
Click the tabs for specific engine information

Full-Size Except Grand Prix L66 200 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.0:1. Horsepower: 200 @ 3800. Torque: 350 @ 2000 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Rochester 7044262.

All Series Except Ventura – L75 250 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.2:1. Horsepower: 250 @ 4000 RPM. Torque: 370 @ 2800 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Rochester 7044262.

Firebird Only, Hydra-matic Transmission – Super Duty 290 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 290 @ 4000 RPM. Torque: 390 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 301°, Exhaust 313°, Overlap 76°, Lift: Intake 0.410″ Exhaust 0.410″. Carburetor: 4-barrel Rochester 7044270.

Firebird Only, Manual Transmission – Super Duty 290 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.4:1. Horsepower: 290 @ 4000 RPM. Torque: 390 @ 3600 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 301°, Exhaust 313°, Overlap 76°, Lift: Intake 0.410″ Exhaust 0.410″. Carburetor: 4-barrel Rochester 7044273.

1975-1976

In the last two years of its life, the 455 was a mere shadow of its former self, used mostly in big Pontiacs, though available across the line, Choked by a single exhaust and a catalytic converter, made a paltry 200 SAE Net HP. Pontiac’s large journal engine went out with a whimper, as did most Detroit big V8s.

1975 – 1976 Pontiac 455 CID Engine Specifications
Click the tabs for specific engine information

1975-76 455 CID 200 HP AMT

Full-Size and Grand Prix 200 HP 455 V-8: Overhead valves. Cast iron block. Displacement: 455 CID. Bore and stroke: 4.155 x 4.2.19″. Compression ratio: 8.0:1. Horsepower: 200 @ 3500. Torque: 320 @ 2000 RPM. Five main bearings. Hydraulic valve lifters. Camshaft Duration: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″. Carburetor: 4-barrel Rochester 7045262.

1955-1982 Pontiac V-8s – Part 4

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