Pontiac Small Journal V8s Described – Part Two

Engine Articles, Most Recent Technical Information, What’s Happening

Pontiac Small Journal V8s Described – Part Two

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.

The large main journal (3.25″) engines were the 421, 428, and 455 V8s.

  • For information on PART ONE of the SMALL journal V8s, click here.
  • For information on the LARGE journal V8s, click here.

Engines are listed in the order of introduction.

Small Crankshaft Journal (3.00″) Engines

The 389 cu. in. V8 (1959-1966)


For 1959 the V8’s stroke was increased to 3.75″, raising displacement to 388.9 cu in. The 389 would remain the standard Pontiac V8 engine through 1966, offered in a huge variety of outputs ranging from 215 to 368 horsepower. (See chart). The 389 was also the power plant for the Pontiac GTO through 1966.

For 1959 the power was again raised, with the base engines between 215 to 260 hp and the performance engines developing anywhere from 280 to 345 hp. The “High Output” versions were labeled “420-A” and were the first of what later would be called “Super Duty” engines.


The 389 was little changed for 1960, however horsepower changed with the base standard transmission 4-barrel engine receiving an upgraded camshaft and 281 hp. On the whole, hp ranged from the 2 barrel economy engine’s 215 to the 389’s 3-2 barrel’s 348 hp.

Beginning in 1960, with the release of the 421 for NASCAR and drag racing, Pontiac also equipped a special series of 389s, called “Super Duty” engines. Super Duty pieces were available over the counter, not factory installed. All SD engines were equipped with special heads with 1.92″ intake and 1.66″ exhaust valves.


Beginning in 1961 the Pontiac V-8s would be called the “Trophy V-8”, to tie it to its many racing victories. The 389 continued with a series of more economical 2-barrel engines added. The regular performance engines remained the same for both 1961 and 1962, however the Super Duty was now a factory option that was available to special dealers and racers.


The regular Pontiac engines in 1962 mimicked the previous year, but certain Super Duty 389s and 421s had 2.02″ intake and 1.76″ exhaust valves, rather than the 1.92″ and 1.66″ valves.


With introduction of the 421 cu. in. HO performance engine, the 348 hp performance 389 was dropped. As such, the 313 hp 3-2 barrel engine, with its tamer camshaft was the highest performance 389 offered. All other 389s offered the same hp as 1962.


For 1964, the 389 returned as a high performance engine in the GTO. Two flavors were offered; 325 and 348 HP. This 389 was quite similar to the original 1960 Super Duty 348 hp engine, with the 1.92″ intake and 1.66″ exhaust�valves.

The 215 hp economy engine was dropped and replaced by the 230 HP auto trans unit from 1963.


In 1965-66 the GTO settled on 335 and 360 hp for the 4-barrel and 3-2 barrel engines. An “X” code ram air engine with an even more aggressive 301/313 cam was introduced in 1966, but advertised hp stayed at 360. Other 389s ranged in hp from 256 to 333 hp, though only the GTO could receive the 3-2 barrel engine.

1966 was the last year for the 389 V8, with a much improved 400 cu. in. motor debuting in 1967.

326 cu. in. V8 (1963-1967)

In 1963 Pontiac dropped the Buick Division-built 215 aluminum V8 offered on the Pontiac Tempest in 1961-62 and replaced it with a small-bore version of the standard 389 Pontiac V8. It shared the 389’s 3.75″ stroke, but its bore was 3.78″ giving this one-year-only cubic inch size of 336. For the remaining 3 years of its life, it would be a smaller bore 326 cubic inch engine.


For 1963 the 336 was rated at 260 hp with 10.25:1 compression and a 2-barrel carb. Later a 4-barrel engine was introduced that was rated at 280 hp. The 336 V8 engine was a high-end engine option for A-body Pontiacs only. Cylinder heads took advantage of the 389 with 1.88″ intakes and 1.60″ exhausts.


For 1964 the 336’s bore was reduced to 3.71875″ (3.72″) but the stroke remained the same, resulting in 326 cubic inches – which it would stay at until it was discontinued at the end of 1967 and replaced with the 350.

With the introduction of the new larger A-Body, a Chevrolet sourced 6 cylinder and the 326 were the only engines offered in the Tempest line, with the exception of the historic GTO, of course, which received the 389. All other Pontiac A-Bodies had a choice of two 326 V8s; a 250 hp 2-barrel carbed version and a higher-output version, which was called the “326 HO” (High Output). The HO had a four-barrel carburetor, dual exhaust, and higher compression, and made 280 hp


The 326 was offered in the same two flavors in the three years after 1964, with the exception that the HO version was rated at 285 hp. In 1967 the Pontiac Firebird, received this engine as the base V8 powerplant. The valve size in ’67 increased to match th elow performance 400 at 1.92″ intake and 1.66″ exhaust�valves.

The 326 was replaced by the 350 cu. in. V8 in 1968.

400 cu. in. V8 (1967-1976)

In 1967, Pontiac introduced the 400 cu in V8. The ‘400’ V8 was a bored-out 389 with a 4.1225″ bore and the 389’s 3.75″ stroke, resulting in 400.4 cu in. It replaced the 389 and remained in production through the 1979 model year.


In 1967, the cylinder head design was improved for all Pontiac engines. The valve angle was changed for better breathing. 1967 was the last year for the old closed chambered heads. This “670” head was a ’67-only casting, and the last PMD head to have a closed combustion chamber.

Pontiac went to open combustion chambered heads in ’67 to improve power, engine breathing and emissions. On all performance engines, the valve size increased as well, to 2.11″ intake and 1.77″ exhaust valves. Low performance and 2bbl applications got 1.96″ intake and 1.66″ exhaust valves and pressed in rocker arm studs.

The 3-2 barrel setup disappeared on GTOs for 1967 as part of a GM edict that only B-C body and Corvette could use multiple carburetion. Horsepower for the new 400 ranged from 265 in the “economy” 2 barrel 8.6:1 GTO egine all the way up to 360 for the Ram Air version.

The standard 1967 360 hp GTO engine is considered the “HO” and the optional, race only version was called “Ram Air 400”. Though they were rated at the same horsepower, they were very different, with the RA 400 receiving a more radical cam and different, freer flowing cylinder heads.


The 400 base engines remained unchanged for 1968, except that the 400 was now available in the Firebird with three special hp ratings – 330 and 335 and 340 with the last two Ram Air I and II engines. The Ram Air II GTO engine replaced the Ram Air I and received a 366 hp rating, though it was far more than 6 hp stouter than the 360 hp HO. It received special round exhaust ports and taller intakes and a different manifold to match the heads.

Later the Ram Air IV was released, and this was an even more special animal, with a special aluminum semi-high rise intake, and heads and a radical 308/320 cam.


In 1969, the standard “street” 400s configured the same as 1968. The Ram Air I and II were discontinued and replaced with the Ram Air IV from last year, a new Ram Air III, and an even more outlandish Ram Air V, rated at 375 hp and running “tunnel port” intake ports along with a mechanical cam withthe same advertised duration as the Ram Air IV’s hydraulic.�

The rest of the Pontiac line remained the same.


With the lifting of the ban on 400 cubic inches, most of GM’s performance engines moved up to the new 455 cu. in limit. Pontiac did offer two 455s that year, but aside from that the 400 still reigned supreme, with all the ram air cars still receiving the options of Ram Air III or IV.

Except for dropping some of the HO 400s for 1970 and replacing them with 455s the 400 still had an active life as the mainstay of V8s in the Pontiac line.


Things changed radically in 1971, with the reduction of compression ratios to meet the soon to be instituted unleaded gas requirements. Only two 400s were offered, and they were equipped with 2-barrel carburetors and 8.2:1 compression ratio. The performance banner woul dnow be carried by the 455.


For 1972, a 4-barrel 400 returned with a weak 250 SAE Net hp rating, but the 400 still only ahd two offerings – 2 and 4-barrel; otherwise they were much the same.


Three 400s were offered in 1973-74, but they were mostly available to pull around bigger cars seeking a bit better fuel mileage. In ’73 two were 2-barrel equipped, in 1974, two were 4 barrel equipped. The 455 was now the performance engine with a SD 455 released for the Trans Am. The newly released GTO was a Pontiac X body Ventura and its powerplant was a 350 with 200 hp. Oh how the mighty had fallen.


Though the 400 would soldier on in the Firebird and would continue to receive a 4 barrel, it was basically a pedestrian engine, though for the period, perky. In 1980, the 400 was quietly dropped.

350 cu. in. V8 (1968-1976)

In 1968 the 326 was replaced by the 350, which used a 3 3.88″ bore and 3.75″ stroke for a total displacement of 354.71 cu in although it was called a 350.


�This engine was offered in both 2bbl and 4bbl variations similar to the previous 326 engine. In 1968 an HO option was available in the Tempest and Firebirds that was rated at 320 hp.


This engine was also offered in 1969 along with a second HO version. The later 350 HO was rated at 330 hp, and was equipped with the 400 CI large valve heads (# 48 with 2.11 intake and 1.77″ exhaust valves) and the 400 HO camshaft (068).


In 1970 the 350 returned to its pedestrian roots, being offered only as a two-barrel. with the 1.96″/1.66″ valves – rated at 255 hp.


The 350 was issued in various forms from 1971-1976, but only in 2-barrel form and with ratings from 150 to 175 hp, SAE net. The 350 disappeared from the lineup after 1976.

303 cu. in. V8 (1969)

In 1969, Pontiac unveiled its Trans Am model Firebird, and since racing rules required a sub-305 cid engine, Pontiac unveiled the 303 for racing models only, never available to the public. Bore and stroke were 4.125″ x 2.8125″, for 300.7 cu in . It was rated at 475 hp.

By the time this engine was ready, Pontiac had agreed not to compete in Trans Am and steal any of Chevrolet’s Thunder. No engines were ever released to the public.


Contributed by Mike Trebuchet – edited by Bob Gerometta

AHPS Car Logo Clear

Eric White Digital Library

Follow Us


Pin It on Pinterest

Share This