Pontiac V8 engine

Pontiac V8 engine

From 1955 to 1981 the Pontiac Division of General Motors manufactured its own, unique V8 engines, distinct from Buick, Cadillac, Chevrolet, or Oldsmobile. Displacement began at 287 in³ and grew as large as 455 in³ (7.5 L) by 1970.

Pontiac's engines were used in its U.S.-market cars; Canadian-built Pontiac automobiles generally used Chevrolet engines. From 1955 through 1959 Pontiac's V8 was also used in GMC pick-up trucks.


The development of Pontiac's OHV V8 dates back to 1946, when engineers began considering new engine designs for postwar cars. Despite these experiments, the division's conservative management saw no immediate need to replace the Pontiac Straight-8 engine, which had served well since 1933. When Robert Critchfield took over as general manager in 1952, however, he launched an ambitious plan to move Pontiac into the upscale, mid-range market segment occupied by Oldsmobile, and that demanded V8 power. The development of the new engine was fast-tracked, but since its relatively late development let it take advantage of the experience gained in the Oldsmobile V8 engine and Cadillac V8 engine, it was remarkably free of teething problems. The main unique feature of the Pontiac engine was the stamped rocker-arm system, which had been devised by Pontiac engineer Clayton Leach in 1948. At the request of Ed Cole, general manager of Chevrolet, the layout was also used by the Chevrolet V8 released in 1955, an exception to the customary GM policy of allowing a division one year of exclusive use of an internally developed advance.

Federal emissions standards and the drive towards "corporate" engines shared among all GM divisions led to the progressive demise of the Pontiac V8 in the late 1970s. The last Pontiac V8, a 301, was produced in 1980 for a 1981 automobile.

Pontiac also had a V8 engine used in 1932 only.during 1951,1952, pontiac had 23 1953 model production prototypes running tests on the gm proving grounds, these 23 cars were equipped with the new 287 V8 engine. pontiac planned to produce the 1953 models with the V8, but buick and oldsmobile feared a sizeable loss in customers, if they had to compete with pontiac having a new V8 engine. after hearing from buick and oldsmobile, gm's board of directors ordered pontiac to delay the V8 introduction until 1955. pontiac's V8 development that started in 1946, was a 269 ci L head design, the 287 ci overhead design started in 1951. pontiac engineers tested their 269 V8 in 1949 or 1950 against a downsized olds rocket V8 overhead engine, the olds engine was a 303 ci, pontiac reduced the size to 270 ci for testing against the 269 engine. the test results showed pontiac that a L head engine couldn't compete with the overhead engines.


The Pontiac V8 was an overhead valve engine with wedge combustion chambers. It used cast iron cylinder heads and a cast-iron block. An innovative design feature was mounting the rocker arms on ball pivots on studs set into the cylinder head, rather than using a separate rocker shaft; this allowed more consistent valve action with less weight than a conventional shaft. All (except the 303 Ram Air V engine and 265 and 301) used 6.625 in (168.3 mm) connecting rods. All Pontiac V8s from 1955 to 1959 were reverse cooled, known as the "gusher" cooling system. It was removed from the design for the 1960 model year due to the fact that pontiac needed to move the generator and the power steering pump from atop the front of the engine down to the front of the heads due to the hoodline getting lower.

Most iterations had an overall length (to the edge of the water pump pulley) of 28.25 in, an overall width of 27 in, and a height (not including air cleaner) of 31 in (718 mm × 686 mm × 787 mm). Dry weight ranged from convert|590|lb|abbr=on to 650 lb (270 to 295 kg), depending on displacement and year. Most Pontiac engines were painted light blue. The 389 version was known as the "Tempest" or "Trophy" V8, depending on year and hp rating. Pontiac was one of a few US manufacturers which did not regularly identify its engine names and sizes with air cleaner or valve cover decals.

Engine Development: Small Journal Engines


The V8 engine was introduced for the 1955 model year as the "Strato Streak". Not long before the model year introduction, Pontiac management decided that the entire line would be V8-powered. This was based on results of over 1 million test miles which was unheard of at the time.

The 287 was an "oversquare" engine with a bore of 3.75 in (95.25 mm) and a stroke of 3.25 in (82.55 mm), for a total displacement of 287 in³ (4.7 L). Compression ratio was a modest 8.00:1, with valve diameters of 1.781 in (45.2 mm) (intake) and 1.500 in (38.1 mm). It was rated 180 hp (134 kW) @ 4600 rpm and 264 lb·ft (358 N·m) @ 2400 rpm with a two-barrel carburetor, 200 hp (149 kW) @ 4600 rpm and 278 lb·ft (377 N·m) @ 2800 rpm with the four-barrel carburetor.


For 1956 the V8 was bored out to 3.9375 in (100.0 mm), increasing displacement to 316 in³ (5.2 L). It was offered in the following forms:

(with manual transmission)
* two-barrel carburetor, 7.9:1 compression, 192 hp (143 kW) @ 4400 rpm, 297 lb·ft (403 N·m) @ 2800 rpm
* four-barrel carburetor, 8.9:1 compression, 216 hp (161 kW) @ 4800 rpm, 315 lb·ft (427 N·m) @ 2800 rpm

(with Hydramatic)
* two-barrel carburetor, 8.9:1 compression, 205 hp (153 kW) @ 4600 rpm, 294 lb·ft (399 N·m) @ 2600 rpm
* four-barrel carburetor, 8.9:1 compression, 227 hp (169 kW) @ 4800 rpm, 312 lb·ft (423 N·m) @ 3000 rpm
* two four-barrel carburetors, 10.5:1 compression, 285 hp (213 kW) @ 5100 rpm, 330 lb·ft (447 N·m) @ 2600 rpm.


The 336 in³ (5.5 L) engine was only used in GMC trucks. The bore was 3.875 (98.4 mm) and the stroke was 3.56 in. (90.4 mm).


For 1957 the V8's stroke was increased to 3.56 in (90.4 mm), for a displacement of 347 in³ (5.7 L). For the first time, Pontiac offered Tri-Power, three two-barrel carburetors with a sequential linkage (replacing the previous dual-quad set-up). Power ratings increased accordingly:

(with manual transmission)
* two-barrel carburetor, 8.5:1 compression, 227 hp (169 kW) @ 4600 rpm, 333 lb·ft (451 N·m) @ 2300 rpm
* four-barrel carburetor, 10:1 compression, 244 hp (182 kW) @ 4800 rpm, 350 lb·ft (475 N·m) @ 2600 rpm

(with Hydramatic)
* two-barrel carburetor, 10.0:1 compression, 244 hp (182 kW) @ 4800 rpm, 350 lb·ft (475 N·m) @ 2600 rpm
* four-barrel carburetor, 10.0:1 compression, 270 hp (201 kW) @ 4800 rpm, 359 lb·ft (487 N·m) @ 2900 rpm
* three two-barrel carburetors, 10.00:1 compression, 290 hp (216 kW) @ 5000 rpm, 375 lb·ft (508 N·m) @ 2800 rpm.

Several dealer-installed camshafts were optional to increase power further to 310 hp (231 kW).

Standard only for the Pontiac Bonneville was Pontiac's first-ever fuel injection system. A mechanical system built by Rochester, it was similar in principle, but not identical, to the contemporary Chevrolet "fuelie". Pontiac did not release official power ratings for this engine, saying only that it had more than Convert|300|hp|kW|-1|abbr=on. Contemporary road tests suggest that it was actually somewhat inferior to the Tri-Power engines, although it did have better fuel economy. Only 630 Bonnevilles were produced for 1957, all of them fuel-injected.


For 1958 the V8's bore was increased again to 4.06 in (103.2 mm), increasing displacement to 370 in³ (6.1 L).

The fuel-injected engine was now an option, not standard, on the Bonneville, carrying a staggering price tag of $500 (almost 15% of the car's base price). It was rated at 310 hp (231 kW) @ 4800 rpm and 400 lb·ft (542 N·m) @ 3,000 rpm on 10.5:1 compression. Only about 400 were produced before the fuel injection system was quietly dropped.


For 1959 the V8's stroke was increased to 3.75 in (95.3 mm), raising displacement to 389 in³ (6.4 L). The 389 would remain the standard Pontiac V8 engine through 1966, offered in a bewildering variety of outputs ranging from Convert|215|hp|kW|0|abbr=on to 360 hp (160 to 269 kW). The 389 was the standard engine for the Pontiac GTO through 1966.


This engine was actually 336 ci in 1963 only, corrected to a 326 in 1964For 1963 Pontiac dropped the Olds/Buick sourced 215 aluminum V8 it had offered on the Pontiac Tempest and replaced it with a small-bore version of the standard 389 Pontiac V8. It shared the 389's 3.75 in (95.3 mm) stroke, but its bore was reduced to 3.72 in (94.5 mm), giving it a displacement of 326 in³ (5.4 L). It is interesting to note that the very first 1963 326 engines used a convert|3.78|in|mm|sing=on bore size for an actual 336 cubic inch displacement. In 1964 Pontiac reduced the bore size to what was correct for convert|326|in|mm of displacement, a convert|3.72|in|mm|sing=on bore. It was rated at 250 hp (193 kW) with 8.6:1 compression and Convert|260|hp|kW|0|abbr=on at 10.25:1 compression. Both used a single, two-barrel carburetor. The 326 subsequently became the optional V8 engine for Tempests, and later the Pontiac Firebird, through 1967.

A higher-output version was offered, called the 326 HO (High Output). It had a four-barrel carb, dual exhausts, and higher compression, and was good for Convert|280|hp|kW|0|abbr=on for 1963-1965, and Convert|285|hp|kW|0|abbr=on for 1966 and the final year, 1967.


For 1967, Pontiac introduced the 400 in³ (6.6 L).

The '400' V8 was essentially a bored-out 389 with convert|4.121|in|mm|sing=on bore and convert|3.75|in|mm|sing=on stroke (104.7 mm by 95.3 mm). It replaced the 389 in 1967 and remained in production through the 1979 model year.

The 400 was the only engine installed in '67-69 Pontiac GTOs. It was also the biggest engine available in '67-'70 Firebirds. The 400 was a popular performance option for many of Pontiac's cars. The 400 engine produces a good balance of low end torque and higher RPM power.

In 1967 the cylinder head design was improved for all engines. The valve angle was changed for better breathing. 1967 was the last year for closed chambered heads. The "670" head was a '67-only casting, and the last PMD head to have a closed chamber. Pontiac went to open chambered heads in '67 to improve power, engine breathing and emissions. The valve size increased as well, to 2.11" intake and 1.77" exhaust valves on high performance heads. Low performance and 2bbl applications got 1.96" intake and 1.66" exhaust valves and pressed in rocker arm studs.

400s were produced until 1979; this was the final Pontiac V8 based on the 1955 design.


In 1968 the 326 was replaced by the 350, which used a 3.875 in bore and 3.75 in stroke for a total displacement of 353.79in³ although it was still called a 350 (5.7 L).


In 1969, Pontiac unveiled it's 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 4.12X2.82. It was rated at 475 gross hp.


The 366 was never intended for production, it was a variant of the 303, only on a tall (normal) deck sharing Ram Air IV or Ram Air V architecture.


The 301 in³ (4.9 L) 301 was offered from 1977 to 1981 and also installed in other GM cars during those years. The 301 had a 4.00 inch (101.6 mm) bore and 3.00 inch (76.2 mm) stroke. Based in part on designs for the "short deck" 303 in³ (5.0 L) engine designed for the 1970 racing season, it had a shorter deck than the big V8, and used thin-wall castings to reduce weight. The crankshafts were also unique in the fact that they featured only two counter weights instead of the usual five, and also featured lightened connecting rod journals. This resulted in a lightweight design weighing less than the Chevrolet small-block V-8. Power output ranged from Convert|135|hp|kW|0|abbr=on to Convert|170|hp|kW|0|abbr=on. The heads were a new design featuring siamesed intake ports. The short-deck block and different intake ports also required the design of a new intake manifold. The Pontiac 301 EC (Electronic Controls) version offered in 1981 produced Convert|155|hp|kW|0|abbr=on and Auto ft.lbf|245|0, although it's rumored that the actual HP was closer to Convert|170|hp|kW|0|abbr=on. The 1980 301 Turbo was rated at Convert|210|hp|kW|0|abbr=on @ 4400 rpm and Auto ft.lbf|345|0 @ 2800 rpm. The 1981 301 Turbo gained the electronic controls with an O2 sensor, feedback ECM and E4ME Quadrajet providing a slight reduction in output to Convert|205|hp|kW|0|abbr=on and Auto ft.lbf|340|0. Although it is much different that the original 1955-vintage Pontiac V-8 powerplant, the 301 has the distinction of being the last true Pontiac V-8 engine as Pontiac ceased production of these engines effective April 1, 1981.

From 1977-1980 there were 4 distinct 301 versions:

301 2BBL (135 hp), 301 4BBL (150 hp), 301 4BBL 'HO' or 'EC' (170 hp), and the 301 Turbo.

The 301 Turbo was unique in that it had a beefier block than the 77-79 versions (which carried on in the non turbo versions in 1980 and 1981), a very mild camshaft with .350-inch lift and 250 degrees gross duration, a 60 psi oil pump to ensure adequate oil to the oil cooled Garrett TBO-305 Turbocharger, a rolled fillet crankshaft, a fully baffled oil pan, and a specific 800 CFM Quadrajet carburator. This 800 CFM Quadrajet had super rich "DX" secondary metering rods and a remote vacuum source for the primary metering rod enrichment circuit that allowed the "PEVR", Power Enrichment Vacuum Regulator to release the primary metering rods to move to the up position (enrichment) anytime during boosted conditions. This was to ensure that there was enough fuel to cool the cast offset dished pistons. Boost was wastegate limited to 9 psi (+/- 1 psi). The 301 Turbo package mandated Air Conditioning, automatic THM350 non-lockup transmission (THM350C lockup in 1981 Trans Ams) and 3.08 gears.

The 301 Turbo was limited to Trans Am and Formula Firebird production only. Some literature has indicated that the 301 Turbo may have found its way into the Chevrolet Z28. It is unclear if any were ever produced.


Based on the same short-deck as the 301, the 265 (4.3 L) was offered only in 1980 and 1981, and featured a smaller bore of 3.75 in (95.3 mm) coupled with the same 3.00 in (76.2 mm) stroke of the 301. It produced 120 hp (90 kW)

Engine Development: Large Journal Engines


Introduced in 1961 as a dealer installed Super Duty option that had dual four barrels, the 421 in³ (6.9 L) was bored to 4.09 in (103.9 mm) and stroked to 4.00 in (101.6 mm), and also featured larger, 3.25 in (83 mm) main journals. Unlike previous enlargements of this engine, it did not replace the 389. The 421 SD became factory installed in 1962 and in 1963 a street version became available from the factory with a four barrel or tri-power carburation. The Super Duty versions of this engine 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. The Armasteel cast crankshaft was the standard crankshaft of the entire Pontiac V-8 line until '67. While "Armasteel" was no more than a fancy name for a hardened cast iron unit, it did refer to the "locking ball" as opposed to the "flaking" type cast iron found in other engines. In '67, Pontiac out of concerns the public misunderstood the engineering terms, went to a Nodular cast iron name crankshaft, which they used until 1975.


In 1967 the 421 was bored to 4.12 in (104.7 mm), increasing its displacement to 428 in³ (7.0 L). The 428 had the same 4.00" stroke as the 421, and was produced from 1967 to 1969. The Crankshaft in the 428 also had a N cast on them as opposed to the 421's armasteel. In 1969, Pontiac also used a revised Crankshaft out of a Pearlitic Malleable Iron although it still used the" N" i.d. cast letter. This new material had stronger alloys in the iron. All 428 engines were factory install in large cars only. However, there were a few dealers that would install a 428 in a customers GTO or Firebird for higher power levels.

It was replaced by the 455 for the 1970 model year.


For 1970, the 428 bore was expanded to convert|4.152|in|mm, combined with a convert|4.21|in|mm|sing=on stroke (105.5 mm by 106.9 mm), yielding a total displacement of 455 in³ (7.5 L). The engine became available for the first time in Pontiac Firebirds and the Pontiac GTO, as GM lifted its restrictions on the use of engines larger than 400 cubic inches (401 in some Buicks) in mid-sized cars. The Pontiac V8 design differs from other manufacturers' designs in that the external dimensions of each engine, from 326 - 455 in³ displacement, is identical. The displacement is determined internally with changes to the bore and stroke; therefore, there is no "big block" Pontiac engine. The 455 was used through 1976.

The 455, with its "undersquare" dimensions (long stroke relative to bore), emphasized torque over hp, and was somewhat less powerful than some high-performance iterations of the 400. For 1971 Pontiac introduced a High Output, H.O., version with standard internal parts, a reinforced block with 4-bolt main bearing caps, and improved cylinder head design with 1/8 inch taller intake ports and special round exhaust ports for better breathing, making some Convert|335|hp|kW|0|abbr=on/224 kW (310 hp in the more accurate SAE net system), but this was an extremely rare engine (it was standard in the Firebird Trans Am. In 1973, a further refined and even stronger version, the Super Duty (SD) engine was introduced with "only" Convert|310|hp|kW|0|abbr=on/231 kW (SAE net) using a similar camshaft specifications to the Ram Air IV 400. The 455 SD used round port cylinder heads similar to those used on the 1971 and 1972 455 HO, with specific "LS2" intake and cast iron exhaust header-manifolds. Still, it was the strongest American engine offered that year. Its power was achieved through bending of EPA emissions-testing procedures, which led engineers to de-tune the engine to 290 hp (216 kW) via a camshaft change to the same profile used in the early RAIII 400 engines for mid 1973 and 1974, after which point it was discontinued.

While an evolution of the RAIV and H.O. engine designs, the 455 SD was a much improved engine. In addition to the more refined cylinder heads, block casting reinforcements in the lifter galley and main bearing oil pan rail area along with the addition of forged connecting rods with larger 7/16 inch diameter bolts, the SD was made with a provision for dry sump oiling from the factory. This truly was a racing engine, detuned for use in passenger cars.

Ram Air

Ram Air

While not officially called the Ram Air I when it was issued, it was indeed the first in a series of Ram Air V8 engines from Pontiac. This engine was installed in the 1967 GTO/Firebird as the top of the line option and at 360 HP (underrated), it was the most advanced 400 in the line. This carried the 301/313 camshaft, as opposed to the "HO" cam which had less duration and overlap. It also had (along with the HO engine) the famous cast iron "headers" which were much better at reducing backflow than the regular manifolds.

Ram Air II

In 1968, Pontiac manufactured the Ram Air II which was a 400 cubic inch motor. In GTO trim the factory rated the car at 366 HP/445 Tq and 'only' 340Hp/430 Tq in the Firebird despite the fact that the engines were identical (save for a small throttle restrictor tab on the Firebird). The Ram Air II was the first engine that incorporated Pontiac's legendary round port head design in a production vehicle. The Ram Air II also incorporated the first computer-designed camshaft. This camshaft sported a wild 308-/320-degree duration with convert|0.470|in|mm|sing=on lift. This same camshaft was also used in Pontiac's 1969-1970 RA IV production cars. The Ram Air II, when outfitted in the (relatively) lightweight 1968 Firebird, has produced some of the fastest 1/4 mile times of the muscle car era. In recent years, under the pure stock drags racing format, Ram Air II Firebirds (running on bias ply tires) have consistently posted ET's in the low to mid 12 second range. No production Pontiac before or since has run times lower. Without question, the RA II was one of Pontiac's most impressive factory offerings.

Ram Air IV

The Ram Air IV replaced the Ram Air II in 1969. The Ram Air IV used the RA II's camshaft but lift in the RA IV was increased to .520 thanks to the use of 1.65 rocker arms (vs 1.50). The RA IV, like the RA II that preceded it, used round port cylinder heads. The RA IV also used a lightweight aluminum intake manifold that produced a weight savings of 10-15 lb. From 1969 though 1970, the RA IV was available in both A-Body (GTO/Judge) and F-body (Firebird/Trans Am) form. While 1969-70 A-body RA IV production was low (1517) only 102 RA IV Firebirds and 55 Trans Ams were built in 1969. RA IV Trans Am production 'jumped' to 88 units built in 1970. Today, any high compression round port Pontiac (i.e RA II or RA IV) is a highly sought after car due to its low production and superior performance on the street and at the strip. After RA IV production ended, Pontiac continued using its round port cylinder head design in 1971. However, by this time compression had dramatically dropped off, marking the beginning of the end of the muscle car era.

Ram Air V

(303, 366, 400, 428)In 1969 Pontiac created several versions of their "tunnel port" engine: a special short-deck version of the V8 for Trans Am racing and a 400 standard deck version. The factory also experimented with 366 and 428 in³ versions. The cylinder head was patterned after the highly successful Ford 427 tunnel port head. So large were the intake ports that the pushrods ran through the center of the ports via pressed-in tubes.

303 - The revised engine had shorter connecting rods, smaller 2.5 in. (63.5 mm) journals, special "tunnel port" heads, and a solid-lifter version of the 400's Ram Air IV camshaft. It shared the 4.125 in (104.8 mm) bore of the 400, but with a 2.84 in (72.1 mm) stroke for a displacement of 303 in³ (5.0 L). The short-deck engine weighed about 40 lb (18 kg) less than the 400, and had an 8000 rpm redline. The 303 program was promising, with race-ready engines producing 475-525 hp (354.4-391.7 kW) and slated for advertised ratings of Convert|355|hp|kW|0|abbr=on in the Pontiac Firebird and Convert|375|hp|kW|0|abbr=on for the Pontiac GTO. Concerns about emissions, the response of the automobile safety lobby, and the warranty implications of a high-revving street engine led to its cancellation. SCCA Trans-Am series General Competition Rules required an engine to be a "Production" item, and required a production of no less than 250 units. The total number of Ram Air V 303 engines produced is not known, estimates range from the SCCA required 250 units, up to 500 units, with rumors of a handful of Ram Air V 303's making their way into the Pontiac Trans-Am production line. These engines are extremely rare and parts not readily available.

The Super Dutys




Available only in the 1973 and 1974 Formula Firebird and Firebird Trans AM. The SD-455 consisted of a strengthened cylinder block that included 4 bolt main bearings and additional material in various locations for improved strength. Original plans called for a forged crankshaft, although actual production SD455s received nodular iron crankshafts with minor enhancements. Forged rods and forged aluminum pistons were specified, as were unique high flow cylinder heads. A camshaft with 301/313 degrees of advertised duration, 0.407 inch net valve lift, and 76 degrees of valve overlap was specified for actual production engines in lieu of the significantly more aggressive RAM AIR IV style cam that had originally been planned for the engine (initially rated at convert|310|hp|abbr=on with that cam), but ultimately proved incapable of meeting the tightening emissions standards of the era. The very modest cam, combined with a low compression ratio of 8.4 (advertised) and 7.9:1 actual resulted in 290 SAE NET HP. The initial press cars that were given to the various enthusiast magazines (e.g. HOT ROD and CAR AND DRIVER) were fitted with the RAM AIR IV style cam and functional hoodscoops - a fact that has been confirmed by several Pontiac sources. Actual production test cars ran considerably slower and yielded 1/4 miles times in the 14.5 second/98 MPH range in showroom tune - results that are quite consistent for a car with a curb weight of 3,850 pounds and the rated 290 SAE NET HP figure that some sources suggest was "under-rated." Various Pontiac sources have emphatically stated that NO convert|310|hp|abbr=on versions of the SD455 were installed in regular production cars. 1975 Factory Service Manual lists the SD455, but the SD455 did not meet emissions for the 1975 model year and was canceled.


While not a V8, the SD4 was the last in a line of high performance Pontiac engines. The SD4 was available in the Indy Fiero. Over the counter parts could garner a 2.7L convert|272|hp|abbr=on version and a 3.2L convert|330|hp|abbr=on version. See the Iron Duke 2.5L 4 cyl engine. [http://en.wikipedia.org/wiki/GM_Iron_Duke_engine]

Pontiac HO engines

326 HO

350 HO

In 1968, There was also a 350 "HO" which had an increased power with the addition of higher compression #18 heads, (#17 and #46 were the most common 2 barrel heads)a 4 barrel carb and matching intake that was also used on the 400 and 428 engines. There was also the addition of dual exhaust, and in the case of a stick shift car, a slightly more aggressive cam.

In 1969, the 350HO was upgraded again with the addition of the 400 HO cam, commonly referred to by Pontiac hobbyists as the 068 cam. Also the addition of #48 casting number heads with a 68 cc chamber for higher compression, along with larger 2.11" & 1.77" valves. Free flowing exhaust manifolds from the 400 RamAir was used late in the model year. This was under rated at convert|325|hp. Many of cousin division more popular Chevolet 350's and even base SS396's were handily beaten by this little 350"High Output"(HO) Pontiac. This may be today one of the most over looked high performance engines of the era, as it was overlooked by the buyers of larger 400 engines available in the day.

400 T/A 6.6

In 1978 the 400 T/A 6.6 was created to fulfill the vacuum of the lackluster 76 455 HO, with improved flow cyl "6X" casting heads borrowed from the 350 yielding higher compression, specific camshaft, 3.23 gearing, and a new dual muffler exhaust making convert|220|hp|abbr=on, providing the Trans AM and Formula Firebird with a breath of new life after some dismal performance years. The 4 speed manual transmission was also available behind the 400 HO and the 301 HO. The 400 T/A 6.6 did not live long however, emission standards and fuel economy restrictions for 1980 model year doomed the powerplant. The 301 Turbo replaced the 400 HO in 1980, disappointing potential customers who were just getting excited about performance returning to Pontiac. The 400 HO Trans AM was the last of the performance cars available with the manual transmission, also yet another disappointment to potential customers.

No hood scoop moniker denoted the 220hp 400 HO except the standard "T/A 6.6". The 185 hp 403 Oldsmobile powered cars had "6.6L Litre". Historically the "T/A" prefix on the hoodscoop noted that it was a Pontiac sourced engine, and those ending in Litre were non Pontiac, with the exception of the 1976 50th Anniversary Pontiac Trans AM model.

1977 also had a T/A6.6 option that was rated at 200 hp.

455 HO

First 455 HO's were seen in the 1971 model year with HD blocks, special large valve heads with screw in rocker arm studs, special aluminum intake with removable exhaust crossover, special streamlined exhaust manifolds, higher lift and larger duration camshaft and 800 CFM Quadrajet carburetor with specific jetting.

The 455 HO's were similar to the yet to come SD455 in 1973/74. The 455 HO was available in the Firebird (base, Forumula and Trans AM), and the LeMans, GTO, T37 and GT37 models. The SD455 took the HO 455 to the next level in durability, power and performance.

Last seen in 1976, ending the era of the 455 HO in lackluster fashion, delivering only a paltry convert|200|hp|abbr=on. It shared nothing with its 1971 brethern except the displacement. Standard in Catalina/ Bonneville Wagons. Option in LeMans, Grand LeMans, Firebird Trans Am, Catalina, Bonneville and Grand Prix.

Details of the 1971 455

Details of the 1972 455

Details of the 1973 455

Details of the 1974 455

Details of the 1975 455

Details of the 1976 455

301 HO

While not "high output" fashion by the 60's and 70's standards and no "HO" moniker on the shaker hood scoop, the 301 did end up with a HO "performance" version, yielding convert|170|hp|abbr=on with only 4.9L CID for the 1979-1981 model years.

The 301 HO was the base Trans AM engine in 1980 and 1981.

Modifications over the std 301 4BBL were the 301 Turbo "301T" block, the ESC (Electronic Spark Control) distributor and controller borrowed from the 301 Turbo which allowed for higher timing without the penalty of engine damaging pinging or preignition, a large 4" ram air duct to the air cleaner, specific carb calibration for the 301 HO, and cam similar in grind to the 220 hp 400 from the 1978-1979 model year. Unfortunately no improvements in casting "01" small valve high velocity heads, which could have yielded greater improvements in power.

Pontiac Experimental V8 Engines

427 Hemi SOHC

Features:Thin Wall, Cast Aluminum Block4.257 Bore x 3.75" stroke (3.0" Mains)Forged Steel 6.625" rods (Ram Air V style)12:1 compressionMechanical Port Fuel Injection

Large Valve Heads: 2.40" Intake Valve2.00" Exhaust Valve

Small Valve High Rpm2.19" Intake Valve2.00" Exhaust Valve

Splayed Main Caps, head bolts tie into main caps. Head bolts do not pull on the cylinder wall causing distortion.Cam Drive: Fiberglass BeltMax RPM (High RPM Engine): >8000 rpmEngine Weight: Estimated Auto lb|550|0 complete

Dimensions:Width: 32"Length: 32"Height: 24.6"

Power:estimated convert|640|hp|abbr=on @ 7500 rpm

421 2 Valve SOHC

3 Valve SOHC

389 4 Valve DOHC

Aluminum right 400

Pontiac Four-Cylinder


Perhaps the most unusual variation of the durable Pontiac V8 was not a V8 at all, but an inline four. Created for the 1961 Pontiac Tempest, it was essentially the right bank of the 389, sharing most of its tooling and many of its parts (more than 120 were identical). The bore and stroke of 4.06 in (103.2 mm) and 3.75 in (95.3 mm) were the same, giving a displacement of 194.4 in³ (3.2 L). This degree of commonality enabled it to be produced on the same lines as the V8, allowing substantial cost savings. A drawback was that the 195 weighed much more than a purpose-designed engine: at about 540 lb (245 kg), it was not substantially lighter than the 389.

The 195 produced 110 hp (82 kW) (gross) at 3800 rpm and 190 lb·ft (258 N·m) at 2000 rpm with a single-barrel carburetor, or 155 hp (116 kW) @ 4800 and 215 lb·ft (292 N·m) @ 2800 rpm with the optional four-barrel carburetor. For 1962 a "power pack" option increased rated power to 166 hp (124 kW).

The Achilles heel of the 195 was engine shake. An inline four-cylinder engine produces unbalanced "couple," shaking in the vertical plane, and modern engineers consider the installation of twin counter-rotating balance shafts necessary for engines much larger than 122 in³ (2.0 L). The V8-based design of the 195 had no such balance shafts, and costs prohibited adding them. The 195 was instead cushioned by flexible rubber engine mounts designed to isolate the engine from the rest of the car, and its forces were further dampened by the Tempest's unusual driveshaft. However, if the engine was out of tune or if a spark plug became fouled, the shaking overwhelmed the dampening of the mounts. A special high-strength timing chain was developed especially for the Tempest 4, since a standard chain would stretch and break rather easily from the inherent vibration in this engine design. The timing chain in the 195 was the same as the 389 initially, the upgraded Tempest chain also works on the V8 engines as a high strength upgrade. As an aside, former Pontiac engineer Malcolm McKellar joked in an interview with "Collectible Automobile" magazine that he and his fellow engineers sometimes called the four-cylinder Tempest "a traveling fatigue machine."

The 195 was dropped after 1963, although Porsche would use a "half-a-V8" inline-four (with a rear-mounted transmission) for its later Porsche 944 model.

ee also

* Pontiac Straight-6 engine
* Pontiac Straight-8 engine
* List of GM engines

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