1955-1982 Pontiac V-8 Engines – Part 4

Pontiac’s Large Journal V-8s came in three sizes: 421, 428, and 455 CID. They were available from 1961-1976.
Shown here is the 421 HO engine available from 1963 through 1966.

Pontiac Large Crankshaft Journal (3.25″) V8s – Part Four: 421, 428 and 455 CID

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

NOTE: Unless designated, specifications are for full size cars.

Engines are listed in the order of introduction by Pontiac.

421 CID V8 (1961-1966)

Introduced in 1961 as a dealer installed Super Duty option (to bona fide 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 421 CID V-8

In 1961 the 421 CID V-8 was only offered with dual four barrel carburetors, and was rated @ 373 HP with the two-4-barrel combination, late in the year, it was rerated to 405 HP utilizing the more radical 308 degree camshaft.

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

Optional Dealer Installed “Super Duty” V-8: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 11.0:1.
Horsepower: 373 @ 5400 RPM.
Torque: 430 @ 4400 RPM.
Valve lifters: Mechanical w/1.65:1 Rocker Arms
Camshaft timing: Intake 300°, Exhaust 304°, Overlap 75°, Lift @ 1.5:1 Rocker: (intake) 0.405″ (exhaust) 0.404″. Lift @ 1.65:1 Rocker: (intake) 0.447″ (exhaust) 0.446″.
Carburetors: two 4-barrel Carter AFB carburetors (front) 3435, (rear) 3433.
Exhausts: Low-restriction dual exhausts.
Ignition: dual-breaker.

Optional Dealer Installed “Super Duty” V-8: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 11.0:1.
Horsepower: 405 @ 5600 RPM.
Torque: 430 @ 4400 RPM.
Valve lifters: Mechanical.
Camshaft timing: Intake 308°, Exhaust 312°, Overlap 83°, Lift @ 1.5:1 Rocker: (intake) 0.405″ (exhaust) 0.404″. Lift @ 1.65:1 Rocker: (intake) 0.447″ (exhaust) 0.446″.
Carburetors: two 4-barrel Carter AFB carburetors (front) 3435, (rear) 3433.
Exhausts: Low-restriction dual exhausts.
Ignition: dual-breaker.

NOTE: Early production 405 HP 421 CID engines used cylinder heads with casting #540306 with 1.92” intake & 1.66” exhaust valves.

1962 421 CID V-8

The 421 Super Duty V-8 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 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

Optional “421 Super Duty” V-8: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 11.0:1.
Horsepower: 405 @ 5600 RPM.
Torque: 430 @ 4400 RPM.
Valve lifters: Mechanical with 1.65:1 rocker arms.
Camshaft timing: Intake 308°, Exhaust 312°, Overlap 83°, Lift @ 1.5:1 Rocker: (intake) 0.405″ (exhaust) 0.404″. Lift @ 1.65:1 Rocker: (intake) 0.447″ (exhaust) 0.446″.
Carburetors: two 4-barrel Carter AFB carburetors (front) 3433  (rear) 3435.
Exhausts: Low-restriction dual exhausts.
Ignition: dual-breaker.

NOTE: Early production 405 HP 421 CID engines used cylinder heads with casting #540306 with 1.92” intake & 1.66” exhaust valves. This head was replaced on a later built engine with the head with casting #544127 with 2.02″ intake & 1.76″ exhaust valves.

1963 421 CID V-8

In 1963 a street version became available from the factory with 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. The HO 4-barrel was rated at 353 HP and the Three 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. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: 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. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 10.75:1.
Horsepower: 353 @ 5000 RPM. 
Torque: 455 @ 3400 RPM. 
Valve lifters: Hydraulic.
Camshaft timing: Intake 292°, Exhaust 302°, Overlap 65°, Lift 0.400″.
Carburetors: Three 2-barrel Rochester carburetors: (front) 7013078 (center Synchromesh) 7023161 (center automatic) 7023162, (rear) 7013079.

Super Duty 421 CID V-8 option in Catalina two-door only: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 11.00:1.
Horsepower: 390 @ 5800 RPM.
Torque: 435 @ 4400 RPM.
Valve lifters: Mechanical. 1.65:1 rocker arms
Camshaft timing:

McKellar #10 Intake 308°,Exhaust 320°, Overlap 87°, Lift: (intake) 0.447, (exhaust) 0.446″
McKellar #11 Intake 312°,Exhaust 324°, Overlap 91°, Lift: (intake) 0.447, (exhaust) 0.446″
McKellar #12 Intake 308°,Exhaust 324°, Overlap 89°, Lift: (intake) 0.447, (exhaust) 0.446″

Carburetor:  Carter AFB 3475S.

NOTE 1: various camshafts were used in this engine.

NOTE 2: The SD engines were discontinued after January 1963.

Super Duty 421 CID V-8 option in Catalina two-door only: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 11.00:1.
Horsepower: 405 @ 5600 RPM.
Torque: 425 @ 4400 RPM.
Valve lifters: Mechanical. 1.65:1-ratio rocker arms.
Camshaft timing:

McKellar #10 Intake 308°,Exhaust 320°, Overlap 87°, Lift: (intake) 0.447, (exhaust) 0.446″
McKellar #11 Intake 312°,Exhaust 324°, Overlap 91°, Lift: (intake) 0.447, (exhaust) 0.446″
McKellar #12 Intake 308°,Exhaust 324°, Overlap 89°, Lift: (intake) 0.447, (exhaust) 0.446″

Carburetors: Two Carter AFB 3433S (Front) 435S (Rear).

NOTE 1: various camshafts were used in this engine.

NOTE 2: The SD engines were discontinued after January 1963.

Super Duty 421 CID V-8 option in Catalina two-door only: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 12.00:1.
Horsepower: 410 @ 5800 RPM.
Torque: 430 @ 4600 RPM.
Valve lifters: Mechanical. 1.65:1-ratio rocker arms.
Camshaft timing:

McKellar #10 Intake 308°,Exhaust 320°, Overlap 87°, Lift: (intake) 0.447, (exhaust) 0.446″
McKellar #11 Intake 312°,Exhaust 324°, Overlap 91°, Lift: (intake) 0.447, (exhaust) 0.446″
McKellar #12 Intake 308°,Exhaust 324°, Overlap 89°, Lift: (intake) 0.447, (exhaust) 0.446″

Carburetors: Two Carter AFB 3433S (Front) 435S (Rear).

NOTE 1: various camshafts were used in this engine.

NOTE 2: The SD engines were discontinued after January 1963.

1964 421 CID V-8

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 ranked cars were all assembled 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 and 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

Base Engine Catalina 2+2. Optional Catalina, Star Chief, Bonneville & Grand Prix: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 10.75:1.
Horsepower: 320 @ 4400 RPM.
Torque: 455 @ 2800 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.409″ Exhaust 0.411″.
Carburetor: Carter  4-barrel Model AFB 3650S (synchromesh), 3651S (automatic).

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

Catalina, Star Chief, Bonneville & Grand Prix HO 421 V-8: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 10.75:1.
Horsepower: 370 @ 5200 RPM. 
Torque: 460 @ 3800 RPM.
Valve lifters: Hydraulic.
Camshaft timing: 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 automatic) 7023162, (rear) 7013079.

1965 421 CID V-8

The entry level big car mover 4-barrel got last year’s 350 HP cam and moved up to 338 HP.  The standard three 2-barrel got tweaked timing and moved up to 356 HP, and the big brother HO 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. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 10.5:1.
Horsepower: 338 @ 4600 RPM. 
Torque: 433 @ 3600 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.409″ Exhaust 0.411″.
Carburetor: Carter  4-barrel Model AFB 3895S (synchromesh), 3898S (automatic).

Catalina, Star Chief, Bonneville & Grand Prix 356 HP 421 V-8: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 10.75:1.
Horsepower: 356 @ 4800 RPM. 
Torque: 459 @ 3200 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.406″ Exhaust 0.408″.
Carburetors: Three 2-barrel Rochester carburetors: (front) 7024078 (center synchromesh) 7025075 (center automatic) 7025074, (rear) 7025079.

Catalina, Star Chief, Bonneville & Grand Prix 376 HP HO 421 V-8: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 10.75:1.
Horsepower: 376 @ 5000 RPM. 
Torque: 461 @ 3600 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.409″ Exhaust 0.409.
Carburetors: Three 2-barrel Rochester carburetors: (front) 7024078 (center synchromesh) 7025075 (center automatic) 7025074, (rear) 7025079.

1966 421 CID V-8

In 1966 a 350 HP 4-barrel engine was considered between the 338 and the HO engines, but not adopted. All HP remained the same; some carb numbers were changed.

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. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 10.5:1.
Horsepower: 338 @ 4600 RPM.
Torque: 433 @ 3600 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.409″ Exhaust 0.411″.
Carburetor: Carter  4-barrel Model AFB 4033S (synchromesh), 4037S (automatic).

Catalina, Star Chief, Bonneville & Grand Prix 356 HP 421 V-8: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 10.75:1.
Horsepower: 356 @ 4800 RPM.
Torque: 459 @ 3200 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.406″ Exhaust 0.408″.
Carburetors: Three 2-barrel Rochester carburetors: (front) 7025078 (center synchromesh) 7026075 (center automatic) 7026074, (rear synchromesh) 7025079 (rear Automatic) 7024079.

Catalina, Star Chief, Bonneville & Grand Prix 376 HP HO 421 V-8: Overhead valves. Cast iron block. Five main bearings.
Displacement: 421 CID.
Bore and stroke: 4.09375 x 4.00″.
Compression ratio: 10.75:1.
Horsepower: 376 @ 5000 RPM.
Torque: 461 @ 3600 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.409″ Exhaust 0.409.
Carburetors: Three 2-barrel Rochester carburetors: (front) 7025078 (center synchromesh) 7026075 (center automatic) 7026074, (rear synchromesh) 7025079 (rear Automatic) 7024079.

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 was now Nodular Iron and identified 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 428 CID V-8

This engine produced 360 HP in standard 4-barrel form and 376 HP in 4-barrel HO form. For the first time the non-HO version utilized different camshafts for the automatic transmission and the manual transmission. The HO retained a single camshaft for both.

1967 Pontiac 428 CID Engine Specifications
Click the tabs for specific engine information

Full Size 360 HP 428 V-8. Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 428 CID.
Bore and stroke: 4.125 x 4.00″.
Compression ratio: 10.5:1.
Horsepower: 360 @ 4600 RPM.
Torque: 472 @ 3200 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.413″.
Carburetor: Carter 4-barrel Model AFB 4242S or Rochester Quadra-Jet 7027262.

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

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

1968 428 CID V-8

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
Click the tabs for specific engine information

Full Size 375 HP 428 V-8 – All Transmissions: Overhead valves. Cast iron block. Five main bearings.
Displacement: 428 CID.
Bore and stroke: 4.125 x 4.00″.
Compression ratio: 10.5:1.
Horsepower: 375 @ 4800 RPM.
Torque: 472 @ 3200 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.413″.
Carburetor: Rochester  4-barrel (manual transmission) 7028263; (automatic transmission) 7028262.

Full Size 390 HP HO 428 V-8 – Manual Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 428 CID.
Bore and stroke: 4.125 x 4.00″.
Compression ratio: 10.75:1.
Horsepower: 390 @ 5200 RPM. 
Torque: 465 @ 3400 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.414″ Exhaust 0.413″.
Carburetor: Rochester 4-barrel Model 7028267.

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

1969 428 CID V-8

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
Click the tabs for specific engine information

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

Full Size 360 HP 428 V-8 – Automatic Transmission:: Overhead valves. Cast iron block. Five main bearings.
Displacement: 428 CID.
Bore and stroke: 4.125 x 4.00″.
Compression ratio: 10.5:1.
Horsepower: 360 @ 4600 RPM. 
Torque: 472 @ 3200 RPM. 
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: Rochester 4-barrel 7029268.

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

Full Size 390 HP HO 428 V-8 – Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 428 CID.
Bore and stroke: 4.125 x 4.00″.
Compression ratio: 10.75:1.
Horsepower: 390 @ 5200 RPM. 
Torque: 465 @ 3400 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.413″.
Carburetor: Rochester 4-barrel 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 455 CID V-8

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
Click the tabs for specific engine information

GTO & Full Size Car 360 HP 455 CID V-8 – Manual Transmission: Overhead valves. Cast iron block.  Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.1251″ x 4.210″..
Compression ratio: 10.75:1.
Horsepower: 360 @ 4600 RPM.
Torque: 500 @ 3100 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift (intake) 0.414″; (exhaust) 0.413″;
Carburetor:  Rochester four-barrel 7040267.

GTO & Full Size Car 360 HP 455 CID V-8 – Automatic Transmission: Overhead valves. Cast iron block.  Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.1251″ x 4.210″..
Compression ratio: 10.75:1.
Horsepower: 360 @ 4600 RPM.
Torque: 500 @ 3100 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift (intake) 0.410″; (exhaust) 0.413″.
Carburetor:  Rochester four-barrel 7040268.

Grand Prix 370 HP 455 V-8 – Manual Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.155 x 4.2.19″.
Compression ratio: 10.25:1.
Horsepower: 370 @ 4600 RPM.
Torque: 500 @ 3100 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.414″ Exhaust 0.413″.
Carburetor: 4-barrel Rochester 7040267.

Grand Prix 370 HP 455 CID V-8 – Automatic Transmission: Overhead valves. Cast iron block.  Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.1251″ x 4.210″..
Compression ratio: 10.75:1.
Horsepower: 370 @ 4600 RPM.
Torque: 500 @ 3100 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift (intake) 0.410″; (exhaust) 0.413″.
Carburetor:  Rochester four-barrel 7040268.

GTO Ram Air 360 HP 455 V-8 – Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 455  CID.
Bore and stroke: 4.1251″ x 4.210″.
Compression ratio: 10.75:1.
Horsepower: 360 @ 4600 RPM.
Torque: 500 @ 3100 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift (intake) 0.410″; (exhaust) 0.413″.
Carburetor:  Rochester four-barrel 7040270

GTO Ram Air 360 HP 455 V-8 – Manual Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 455  CID.
Bore and stroke: 4.1251″ x 4.210″.
Compression ratio: 10.75:1.
Horsepower: 360 @ 4600 RPM.
Torque: 500 @ 3100 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift (intake) 0.414″; (exhaust) 0.413″.
Carburetor:  Rochester four-barrel 7040273.

Full Size Car 370 HP 455 V-8 – Automatic Transmission: Overhead valves. Cast iron block.  Five main bearings.
Displacement: 455  CID.
Bore and stroke: 4.1251″ x 4.210″.
Compression ratio: 10.25:1.
Horsepower: 370 @ 4600 RPM.
Torque: 500 @ 3100 RPM.
Valve lifters: Hydraulic.
Camshaft duration:  Intake 273°, Exhaust 289°, Overlap 54°, Lift (intake) 0.410″; (exhaust) 0.413″.
Carburetor:  Rochester four-barrel Model 7040268

1971 455 CID V-8

The tables were turned in 1971 when the new low compression made the RAM Air 400 CID cars untenable. The 455 CID engine moved to the forefront, with  280 HP, 325 HP and 335 HO versions.

The 335 HP HO (Option LS5) was a true performance engine. It included the 4-bolt main caps and a reinforced block, along with an improved cylinder head design with 0.125″ inch taller intake ports as well as the special round exhaust ports for better breathing. as such, it made 310 HP SAE Net. This was a rare engine in the mid-size line but was standard in the Firebird Trans Am. The Ram Air of the LS5 versions only differed from the non-air versions by their specially calibrated carburetor.

1971 Pontiac 455 CID Engine Specifications
Click the tabs for specific engine information

Full Size Cars Except Grand Prix. L66 280 HP 455 V-8 – Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 2-barrel Rochester 7041064.

NOTE: This engine was NOT available on LeMans, Grand Prix, GTO, or Firebird.

All Series – L75 325 HP 455 V-8 – Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 4-barrel Rochester 7041262.

NOTE: This engine was NOT available with manual transmission.

455 CID LS5 Option. 335 HP 455 V-8. LeMans, Firebird and GTO only – Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″.
Carburetor: 4-barrel Rochester 7041268.

NOTE: This engine was NOT available in full-size cars or Grand Prix.

455 CID LS5 Option. 335 HP 455 V-8. LeMans, Firebird and GTO only – Manual Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″.
Carburetor: 4-barrel Rochester 7041267.

NOTE: This engine was NOT available in full-size cars or Grand Prix.

455 CID LS5 Ram Air Option. 335 HP 455 V-8. LeMans, Firebird and GTO only – Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″.
Carburetor: 4-barrel Rochester 7041270.

NOTE: This engine was NOT available in full-size cars or Grand Prix.

455 CID LS5 Ram Air Option. 335 HP 455 V-8. LeMans, Firebird and GTO only – Manual Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″.
Carburetor: 4-barrel Rochester 7041273.

NOTE: This engine was NOT available in full-size cars or Grand Prix.

1972 455 CID V-8

This year was a retrenchment for Pontiac, with only 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.

Horsepower ratings moved to SAE Net, drastically revising the appearance of power.

1972 Pontiac 455 CID Engine Specifications – All Horsepower Rating are now SAE Net
Click the tabs for specific engine information

Full-Size Cars Only – Except Grand Prix. Option L66 – 185 HP 455 V-8. Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.155 x 4.2.19″.
Compression ratio: 8.2:1.
Horsepower: 185 @ 4000 RPM;
Torque: 350 @ 2000 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 2-barrel Rochester 7042064.
Exhaust: Single.

Full-Size Cars Only – Except Grand Prix. Option L66 – 200 HP 455 V-8. Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.155 x 4.2.19″.
Compression ratio: 8.2:1.
Horsepower: 200 @ 4000.
Torque: 370 @ 2000 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 282°, Overlap 55°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 2-barrel Rochester 7042064.
Exhaust: Dual.

Full Size Car Only. Option L75 – 220 HP 455 V-8. Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.155 x 4.2.19″.
Compression ratio: 8.2:1.
Horsepower: 220 @ 3600 RPM.
Torque: 350 @ 2400 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 4-barrel Rochester 7042262.
Exhaust: Single.

Full Size, Mid-Size & Grand Prix only Only. Option L75 – 250 HP 455 V-8. Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 4-barrel Rochester 7042262.
Exhaust: Dual.

NOTE: Not Available in Firebird.

Mid-Size and Firebird Only. Option LS5 – 300 HP 455 V-8. Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″.
Carburetor: 4-barrel Rochester 7042270.

NOTE: Standard in Firebird Trans AM.

Mid-Size and Firebird Only. Option LS5 – 300 HP 455 V-8. Manual Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 288°, Exhaust 302°, Overlap 63°, Lift: Intake 0.410″ Exhaust 0.413″.
Carburetor: 4-barrel Rochester 7042273.

Mid-Size and Firebird Only. Option LS5 – 300 HP 455 V-8. Manual Transmission: 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 455 CID V-8

In 1973, a further refined and even stronger version of the 455 CID V-8 appeared. It was called the “Super Duty” (SD) 455 was introduced with “only” 310 HP SAE net. It used a similar camshaft with specifications similar to the 1970 Ram Air IV 400. This 455 SD had round port cylinder heads similar to those used on the 1971 455 HO, with a specific “LS2″ intake manifold and cast iron exhaust header-like manifolds.  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. It also featured 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. It was certainly the most powerful factory installed V-8 engine offered that year.

NOTE: This engine was listed as available in the Firebird, Mid-Size and the Grand Prix, but there is no evidence that it was installed in anything other than the Firebird.

Other pedestrian 455s was available. In the full size, a 215 HP version and in all other Pontiacs, another rated at 250 HP.

1973 Pontiac 455 CID Engine Specifications – All Horsepower Rating are now SAE Net
Click the tabs for specific engine information

Full-Size Cars Except Grand Prix. 215 HP 455 V-8 – Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.155 x 4.2.19″.
Compression ratio: 8.0:1.
Horsepower: 215 @ 3600.
Torque: 350 @ 2400 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 4-barrel Rochester 7043262.
Exhaust: Single.

All Series Except Ventura – Option L75 250 HP 455 V-8 Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 4-barrel Rochester 7043262.

Firebird Only – Option L75 250 HP 455 V-8. Manual Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 4-barrel Rochester 7043265.

Mid-Size, Grand Prix, & Firebird Only – Super Duty 310 HP 455 V-8. Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.  Valve lifters: Hydraulic. Camshaft timing: 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.

Mid-Size & Firebird Only – Super Duty 310 HP 455 V-8. Manual Transmission: Overhead valves. Cast iron block. Five main bearings.
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.  Valve lifters: Hydraulic. Camshaft timing: Intake 308°, Exhaust 320°, Overlap 87°, Lift: Intake 0.470″ Exhaust 0.470″. Carburetor: 4-barrel Rochester 7043273.

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

1974 455 CID V-8

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 still used round port cylinder heads similar to those used on the 1971 455 HO, with the specific “LS2″ intake and cast iron exhaust header-like manifolds. 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. It was still considered the most powerful factory installed V8 engine offered that year.  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 – All Horsepower Rating are now SAE Net
Click the tabs for specific engine information

Full-Size Cars Except Grand Prix. 215 HP 455 V-8 – Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.155 x 4.2.19″.
Compression ratio: 8.0:1.
Horsepower: 215 @ 3600.
Torque: 350 @ 2400 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 4-barrel Rochester 7044262.
Exhaust: Single.

All Series Except Ventura and Wagons – Option L75 250 HP 455 V-8 Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 4-barrel Rochester 7044262.
Exhaust: Dual.

Firebird Only – Super Duty 290 HP 455 V-8. Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
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.
Valve lifters: Hydraulic.
Camshaft timing: Intake 301°, Exhaust 313°, Overlap 87°, Lift: Intake 0.470″ Exhaust 0.470″.
Carburetor: 4-barrel Rochester 7044270.

Firebird Only – Super Duty 310 HP 455 V-8. Manual Transmission: Overhead valves. Cast iron block. Five main bearings.
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.  
Valve lifters: Hydraulic.
Camshaft timing: Intake 301°, Exhaust 313°, Overlap 87°, Lift: Intake 0.470″ Exhaust 0.470″.
Carburetor: 4-barrel Rochester 7044273.

1975-1976 455 CID V-8

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.

1975-76 Pontiac 455 CID Engine Specifications – All Horsepower Rating are now SAE Net
Click the tabs for specific engine information

Full-Size  and Grand Prix 200 HP 455 V-8. Automatic Transmission: Overhead valves. Cast iron block. Five main bearings.
Displacement: 455 CID.
Bore and stroke: 4.155 x 4.2.19″.
Compression ratio: 8.0:1.
Horsepower: 200 @ 3500.
Torque: 330 @ 2000 RPM.
Valve lifters: Hydraulic.
Camshaft timing: Intake 273°, Exhaust 289°, Overlap 54°, Lift: Intake 0.410″ Exhaust 0.414″.
Carburetor: 4-barrel Rochester (1975) 7045262; (1976) 17056262.
Exhaust: Single Catalytic Converter.

Learn About the Pontiac Small Journal V-8 Part 1
Learn About the Pontiac Small Journal V-8 Part 2
Learn About the Pontiac Small Journal V-8 Part 3
Learn More! View Our Pontiac Fact Sheets

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