1971 Pontiac GTO 455 RPO L-75 325HP & 455Ft/lbs Brought Home



I found a Drag Race Gear I like Grumpy.
For Dragstrip Track use only.
I would have to use a Muncie Close Ratio 2.20 1st gear to make the most of it.
I have a New Richmond Gear Gearset in the box for a Pontiac 9.3. 1957-64 Drop out rear.
$400 I paid for it. Will work nice Street Strip. Re Ran the Math today.
Will work nice with a Nitrous shot 125-400 HP.

Normal aspirated power lasts longer .
10,000 miles of full on Race Use Is what I can expect typical and thats very good.

Most Chevies done blow up after 1,000 miles Full Race.

I should buy my Drag gear soon.
Still $400.00.

Stock piling paychecks .
Put away.
The Conservative way.

Not Luberal way.



Rear-End Gearing Simplified

A lot of people don't understand the importance of rear-end gearing, or what kind of gears to choose for their particular vehicle, so I thought I'd take some time to try to simplify it so you can understand it better.

First off, regardless of what kind of engine you have or how much power it makes, gearing can make or break your car. In other words, having the wrong gear ratio can turn your car into a complete and utter turd, or it can make it lightning quick off the line but no with top-end speed what so ever.

"Tall" gears and "short" gears are referring to the gear ratios. Tall (high) gears have LOWER numerical numbers such as 2.79, 2.90, 3.00, 3.25. Short (low) gears have HIGHER numerical numbers, such as 4.11, 4.30, 4.56, 4.88, 5.13, 5.36, etc. In simple terms, the numbers mean how many turns of the drive shaft to one turn of the rear wheel. If you are cruising down the freeway at 60 MPH with 3.00 gears, in a typical high gear with a 1:1 output ratio, it simply means that the drive shaft (engine) is spinning 3 times for every 1 rotation of your tire. If you had something like 4.88's, then your drive shaft (engine) would need to spin almost 5 times for every one rotation of the tire.

So think of it like this, ride a 10 speed bike. Take off in 1st gear. That's a low gear ratio. You can go from 0 - about 5 MPH in a split second, do wheelies, ride up hills, etc quite easily. Now try to do the same thing in a taller gear, like 6th or 7th. Now you can't take off the line very fast, you can't do a wheelie, and you'll fall on your face trying to ride up a hill. It takes much more leg power to "pull" that taller gear, just like taller gears in a car need engines with more power (TORQUE, not "horsepower"), to pull those taller gears. If you want to cruse down the highway on your 10 speed bike, can you leave it in 1st gear? No, because your legs can't go fast enough to keep up as the bike goes faster. Short (low) gears work the same way. They require less power, and accelerate from a dead stop much quicker than taller gears, but you can't cruise very fast down the road without running out of leg RPM. Well, if you plan on doing a lot of freeway driving, you don't want to choose a gear that's too low for your car because you'll be going down the freeway at too high of an RPM.

Rear end gears (2.79’s, 3.00’s, 3.25's, etc) are great for freeway driving, bit not good for 0-60 MPH or accelerating from a dead stop. Shorter gears (higher numbers) are much better suited for accelerating, such as 3.55, 3.73, 3.91’s, 4.11’s etc. Always remember, for very “give” there is a “take”. If you take lower gears to accelerate quickly from 0-60, you will give top-end speed.

Think of it like this; let's say you could only have 1 gear on a 10 speed bike. If you rode around town a lot, then something equivalent to 2nd or 3rd gear would be good to have so you can take-off from stop signs and accelerate quickly through traffic, but if you are going to be riding long distances along the highway, then something like 6th or 7th gear would be a better choice. You won’t be able to get-up and go from a dead stop very quickly, but you will be able to cruise along at 30 MPH pretty easily along the highway without your feet going round and round at 10 million miles per hour. Think of your feet as your engine and the bike’s gears as your car's rear-end gearing. Low gears like 1st, 2nd and 3rd will give you the gitty-up and go from a dead stop, and higher gears will allow you to cruise better at fast speeds.

With cars you need to pick a happy gear that works with your engine and driving needs. Smaller, high winding engines that make good “peak” power need lower gears or they will fall on their face. Big, torquey engines can “pull” taller gears easier and don’t need short (low) gears as much as a smaller engine does. No matter how powerful the engine is, if the gearing isn't low enough, it won't accelerate. Arnold Schwarzenegger couldn't do a wheelie on a 10 speed bike if it was in 10th gear, but an 8 year old kid can if it's in 1st gear. Cars and engines are no different. Just because you may have a powerful engine doesn't mean you'll be "quick" or will accelerate quickly if you don't have gears low enough. Race cars don't run super low gears for no reason. Even with VERY powerful engines, without the gearing, an 8 second drag car can instantly become an 11 second car.

Aside from engine size and power, you also have to take into consideration your tire diameter, transmission type and final drive ratio, the speed you’ll mostly be driving at (town or highway), and calculate the gearing from there. It may sound complicated but it isn’t really. On a 10 speed bike, do you have troubles figuring out which gear to change to as you go faster or slower? Car gearing is no different once you know the info and what to take into consideration. This is why good car builders always have quicker / faster cars than the average guy. They take the whole picture, (the car, engine, gearing, driving style, etc) into consideration so the car can perform as it is intended.

To make a point, if you took a bone stock V-8 car with say, 275 - 300 HP and put 4.88's in the rear-end and ran it against a car with a 750 HP race engine that has 3.00 gears in the rear-end, I guarantee you the bone stock car WILL out accelerate the race car from 0 - 60 MPH, just like an 8 year old kid on a 10 speed taking off in 1st gear will get-up and go to about 5 MPH or so quicker than a bike ridden by someone like Arnold Schwarzenegger could in 10th gear. A car's performance isn't solely related to just the engine's power. Gearing is every bit as important if you want it to go like it's supposed to.

When I was younger and was the "John Milner" of my town with the quickest car in the valley, a lot of people thought it was because I had such a bad ass engine in my car. Indeed for a small block it WAS a bad ass little engine, BUT what most people didn't know was hiding in my rear-end was a set of 4.88 gears. Without those I wouldn't have had a 10 second street car, it probably would have been more like a 12 or 13 second car.








I was driving home from work last night Grumpy in the Suburban and spotted a Hellcat.
Just 2 blocks from the work Raceshop in Chitown.
2015 Hellcat Challanger. All Black.
A Babyboomer driving it about 53-57 years old.
We were on a 2 lane city street going opposite ways.

The Hellcat did not sound all that tough.
Sounded like a Dodge Viper.
I have raced them in the past on Interstate 80 and Blew thier doors off with the Trans Am.
Hellcat is Definitely 10.5 ET Fast with a Drag Rscer like me piloting it.

My Ram Air IV Trans Am Sounds much better.
Full Race Cammed.
The Ground Shakes.
Ear Drum Piercing Loud at 7,000 + RPMS.


For the last time Grumpy Edelbrock heads out of the box have a terrible E/I Ratio.
I have no desire to run pump gas
Race Fuel 110 motor octane or better.
Nothing better bone stock what I have now.
1970 Ram Air IV 614's.

E heads will work.
Professional porting Required .
Race Cam.
$5,000 dollars cash later.


I bought a set of these Remflex 2.000" Ram Air4 Header gaskets to try out.
And matching 3-1/2" Collector gaskets.

Also a Set of Remflex Exhaust manifold gaskets for my 1965 Olds 425A engine.
All in this week.
Summit Racing.
Dropped shipped from the manufacturer.


solid fixture here in the forum
Staff member
Brian, Grumpy, I really need you help with identifying Pontiac set ups. I asked this before a couple of times, I guess it went unread and missed.
I have to pay and pick up that 1970 455 this weekend. I've been asking the sellers to pull the casting numbers to save me a trip in case something isn't right. They say it's too far back and hard to get to and haven't got the numbers yet. I can only assume they're waiting for me to dig this motor out. I'm tired of going out to look at "455" motors only to find out they're a 350 or a 400 (sellers don't think about the size casting in the block.
Anyway, I trying to avoid buying something that won't work out.
Is there any list of head numbers, good to bad? How about the motor it's self? The WC, the WFs, the Y somethings. Like I said before, I'm not interested in the 185 hp, 8.0 :1 compression motors. If I can find a decent hp/tq motor and it can run well without making strange noises or smoking I will just drop it into the '65, drive it and restore it later.
I know that Pontiac like other GM cars switched to the net hp/tq ratings from the gross rating but was it in 71 or 72? It looks like Pontiac was a year ahead of Chevy on that issue. I don't have anything on 1970 just 71 and up. Did compression go down 70 to 71 or was it just gross to net SAE hp and tq ratings?


455 Is Casted on the outside of the Block next to the motor mounts pads.

I never photograpged my 1970 Bonneville 455 up real close.
Its pictured in this thread too.

There was no crappy 455 built.
Ditto for 400 & 350 Pontiac too.

See what I can put together tonight to help you.


Pontiac DIY


You are here: Home / Pontiac Engines / Pontiac V8 Engine History: 1955-1981
Pontiac V8 Engine History: 1955-1981
February 19, 2015 by Pontiac DiY

The Oakland Motor Car Company was founded in Pontiac, Michigan, in the early 1900s, and within a few years, it became a division of the newly formed General Motors Corporation (GM). Falling between Chevrolet and Oldsmobile on the corporate ladder, Oakland introduced Pontiac in 1926 as a companion model line. The Pontiac line proved to be popular and in 1932, General Motors discontinued Oakland, and the Pontiac Motor Car Company was officially formed.

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Oakland introduced the Pontiac in 1926 to complement itself. Pontiacs sold so well that the Oakland line was canceled within a few years. This particular 1926 Pontiac is part of the General Motors Heritage Collection and was the first Pontiac ever produced. It’s the patriarch of the Pontiac hobby that maintains a strong following today.

Pontiac Motor Car Company became Pontiac Motor Division (PMD) in the early 1930s and developed a 268-ci “Straight-8”, which was quite reliable.

V-8 Development
In 1954, General Motors leaned heavily on Chevrolet and Pontiac to develop V-8 engines for the 1955 model year and provided them with all available resources to ensure success.

Pontiac settled on a 3.75-inch bore and 3.25-inch stroke to produce a 287-ci package. Pontiac management urged that the design allow for future displacement increases, which eventually permitted the basic combination to displace 455-ci in a matter of years.

The V-8 Reaches Production
Pontiac’s 287 block featured five 2.5-inch-diameter main journals that support a forged-steel crankshaft. The left-hand cylinder bank was offset rearward. This allowed the distributor to be mounted on the right side of the block, exposing its driven gear to upward thrust, eliminating the need for a machined thrust surface within the block.


The new OHV V-8 “Strato Streak” engine debuted in 1955. Displacing 287 ci, the entry-level 2-barrel mill was packed full of cutting-edge features and was rated at 173 hp. An optional 4-barrel carburetor was made available midyear, which increased horsepower to 200.

The cylinder heads incorporated 1.78-inch intake and 1.5-inch-diameter exhaust valves. A reverse-flow cooling system directed coolant toward the cylinder heads before the lower end of the engine in an attempt to extend exhaust valve life.

The block’s lifter galley was fed with a relatively high volume of oil to accommodate hydraulic valve lifters to provide quiet, consistent, and maintenance-free valvetrain operation. The rocker system, consisting of a stamped-steel rocker arm pivoting on a single stud, was one that many other manufacturers adopted for their V-8s in later years.

Engines featuring a compression ratio of 7.4:1 were rated at 173 hp. A machined (decked) cylinder head was utilized to boost compression ratio to 8:1, and increased horsepower to 180. A 200-hp version was introduced in mid 1955 when a 4-barrel carburetor was made available.

Growth Spurts
Engine displacement grew to 316.6 for 1956, and horsepower increased to 205 for the 2-barrel and 227 for the 4-barrel. Optional dual exhaust added about 10 hp to either engine. Pontiac created its first extra-horsepower package in mid 1956. With more compression, dual 4-barrel carburetors, and a special camshaft, the combination boosted horsepower to 285.


Bunkie Knudsen was brought in to change Pontiac’s image. Though his influence is felt in 1957 model year styling, this 1958 Bonneville represents the direction Pontiac was headed during the late 1950s and into the 1960s. The low-slung body with flashy accents made the Pontiac seem as if it’s moving forward while standing still.


Tri-Power was introduced in 1957 to give Pontiac a youthful appeal to young hot rodders. Boasting excellent street manners and economy while operating on its center 2-barrel carburetor, and strong acceleration as its end 2-barrels progressively opened, it was well marketed and quite popular with buyers through 1966. It is truly a Pontiac trademark.

Semon “Bunkie” Knudsen was appointed as Pontiac’s general manager toward the end of the 1956 model year. With the promotion came instructions to drastically change the division’s image beginning with 1957. In addition to revisions he made to body styling, Knudsen hired Pete Estes who was part of Oldsmobile’s very successful highperformance V-8 program—as chief engineer, and a young John Z. DeLorean as assistant chief engineer.

Even though General Motors agreed to adhere to the Automobile Manufacturer’s Association (AMA) 1957 recommendation, which stated that manufacturers should refrain from encouraging any type of speed or acceleration-related contests, Pontiac increased V-8 displacement to 347. A trio of 2-barrel carburetors, heralded as “Tri-Power,” was made optional, increasing horsepower to 290. The top performer designated for NASCAR-type competition still utilized dual 4-barrel carburetors and cranked out 317 hp.

The Super Duty Era
Displacement increased to 370 for 1958 and horsepower increased accordingly. The engine grew yet again in 1959 to 389 ci, and it remained at this size for 1960. That year also initiated Pontiac’s illustrious “Super Duty” era.

A complete over-the-counter parts package with the sole intent of producing a competition-only 389 was released in 1960. It employed the same four-bolt block used in Tri-Power applications, but the Super Duty package filled it with a forged-steel crankshaft and connecting rods. High-flow cylinder heads produced 10.5:1 compression and a solid-lifter camshaft with 1.65:1-ratio rocker arms controlled valve action. High-flow castiron exhaust manifolds (with separate collectors that could be uncapped) were offered, and a single 4-barrel or Tri-Power intake manifold was also used.

Actual output of the Super Duty 389 wasn’t published, but certain racing series required that manufacturers provide a horsepower rating, so Pontiac arbitrarily rated the 4-barrel engine at 348 hp while the Tri-Power was rated at 363. The combination was quite successful as Pontiacs went on to win 7 of the 44 NASCAR races in the 1960 season, and Pontiac ad-man Jim Wangers piloted a 1960 Ventura to the NHRA National championship.

The 389 was carried over into the 1961 model year and the Super Duty package went on. Intake manifold choices were limited to a single 4-barrel or Tri-Power. While both were previously cast iron, for 1961 they were cast in lighter weight aluminum. Either engine was rated at 368 hp.


Initially available through its dealership parts counters for the Tri-Power 389 in 1960, Pontiac’s Super Duty package included a forged-steel crankshaft and connecting rods, a solid-lifter camshaft, and high-flow cylinder head and exhaust manifolds. The package was available in 1961 with few enhancements, and it continued as a parts department purchase.


Royal Pontiac in Royal Oak, Michigan, capitalized on Pontiac’s success on the drag strip early on. With the assistance of Pontiac ad-man Jim Wangers, Royal Pontiac became intertwined with the Division and had a direct line to its Engineering department. This particular 1961 Ventura, campaigned by Royal Pontiac and driven by Wangers, may be the only 1961 Pontiac to receive a factory-installed Super Duty 389.


To maintain competitiveness on the track with the larger engines produced by other manufacturers, Pontiac released a 421 version of its Super Duty package through its parts departments toward the end of the 1961 model year. To comply with rules imposed by racing associations, both it and the Super Duty 389 became factoryinstalled options in 1962. Available only with two 4-barrels, the SD-421 was rated at 405 hp and made quick work of the competition.


Concerned with maximum performance, little regard was given to cold-weather operating characteristics of the Super Duty engine. As such, most Super Duty Pontiacs were purchased with the sole intent of regularly competing on the race track. Campaigned by Gay Pontiac, driver Don Gay claimed the 1963 NHRA National Championship in class A/Stock with this 1962 Catalina.

The Super Duty combination proved to be lethal. Pontiac was dominating drag strips around the country and it captured 30 of 52 NASCAR race wins during the 1961 season. The 421-ci V-8 debuted in Pontiac’s parts books toward the end of the 1961 model year and was a direct response to Chevy’s 409, Ford’s 406, and Mopar’s 413. It’s generally accepted that none were factory installed.

The Super Duty 421 was comprised of a new 4.09-inch bore block with four-bolt main caps, a forged-steel 4-inch stroke crank, forged-steel connecting rods, and forged-aluminum pistons. It utilized the same cylinder heads as the 389, which pushed compression to 11.0:1, a castaluminum dual 4-barrel intake manifold, and a solid-lifter camshaft. Rated at 373 hp, the package made Pontiac an even greater threat on the race track.

If success is measured by competitive wins, Pontiac was the manufacturer to beat in 1962. The possibilities seemed limitless with the persuasive John DeLorean having been promoted to chief engineer the previous year.

Until that point, certain forms of racing simply required that a given component have a factory part number for it to be legal for competition. That translated into a flood of aftermarket components arbitrarily hung with manufacturer part numbers with the sole intent of satisfying these governing bodies. It didn’t take long for the National Hot Rod Association (NHRA) to catch on and revise its ruling for certain stock classes. Such components not only needed to have a manufacturer’s part number, but they had to be factory-installed too.

Pontiac responded with the announcement of a series of “special purpose” factory-built vehicles. This simply meant that Pontiac installed both the SD-389 and SD-421 into vehicles on its assembly line. The SD-389 was limited to a single 4-barrel while the SD-421 used dual 4-barrels. Both engines received the McKellar number-10 camshaft, which was much like a solid-lifter version of the hydraulic number-041 of later years. The SD-389 was rated at 385 hp, while the SD-421 was at 405.

The 1963 Super Duty 421 received new pistons, which raised the compression a full point over the previous year to 12:1. The single 4-barrel version was rated at 390 hp, while the dual 4-barrel unit was rated at 405 hp as in 1962, even with the increased compression ratio. A separate dual 4-barrel engine with 13:1 compression was also available in 1963, and it was (under)rated at 410 hp.

Pontiac released a revised cylinder head for its Super Duty engines early in 1963. Boasting improved exhaust flow, it had no official effect on output rating.

The Corporate Edict
The bottom seemingly fell out of the performance car market at General Motors in January 1963. GM Chairman Frederic Donner issued a memo to all divisions reaffirming its position on the AMA agreement against racing.


When General Motors pulled the plug on factory-backed racing, Pontiac moved forward with its street performance program. A new vehicle based on the concept of combining a large-cube engine with a compact body produced the GTO for 1964. Corporate regulations limited engine size to 389 in the Tempest platform. Many purists argue that the GTO was America’s first muscle car, initiating the era of serious performance.


In addition to the induction changes for 1967, Pontiac also increased displacement and revised the cylinder head valve angles to improve airflow and further enhance output. The GTO’s 360-hp 389 grew to 400 and the new 4-barrel engine was every bit as powerful as the former Tri-Power mill. (Photo Courtesy Tom DeMauro)

This meant that manufacturers couldn’t openly sponsor race programs, and that experimental components had to be covertly supplied to racers. Vehicles were produced for a few months even after the edict was imposed, however, as evident with the “Swiss Cheese” Catalinas, but General Motors was serious and its Divisions were forced to comply. Pontiac utilized the experience gained from the Super Duty program to create its newest performance street engine, the 421 High Output (421 H.O.).

The 421 H.O. was essentially a detuned SD-421. It consisted of a four-bolt block and number-716 cylinder heads, which were similar to the Super Duty units but contained an exhaust crossover to improve cold-weather operation. An aggressive hydraulic-lifter camshaft was employed, and it utilized Tri-Power induction and high-flow cast-iron exhaust manifolds. It was rated at 370 hp.

A new performance Pontiac entered the market in 1964 and it changed the industry forever. The new “GTO” was built on the intermediate Tempest platform. The 421 H.O. seemed to be a natural fit for the new GTO, but GM’s power-toweight- ratio standards limited maximum engine size to just 389, so Pontiac simply created a 348-hp 389 using components familiar to the 421 H.O.

DeLorean Promoted
John DeLorean was promoted from the position of Chief Engineer to General Manager in 1965. His rebellious attitude allowed him to push many of his technological visions through to production.

Pontiac engines had typically been painted a shade of green or blue up to this point. DeLorean wanted buyers to find the vehicle’s engine as attractive as its exterior, so in 1966 the Pontiac V-8 was painted a light metallic-blue, and a chrome-plated air cleaner and valve covers were added in performance applications.

Though the same engine packages were carried over, the Tri-Power’s end carburetors were made larger for improved airflow, and that boosted horsepower of engines so equipped. A dealer-installed “Ram Air” package was made available for the GTO late in the 1965 model year. The hood scoop insert was cut open, allowing the engine to ingest cooler outside air, conceivably producing more power. The Ram Air package became a Pontiac trademark for years to follow. It never increased the advertised output rating, but it certainly offered a performance benefit.

Major V-8 Design Changes
Pontiac was forced to abandon its signature Tri-Power induction system in 1967 when General Motors banned multiple carburetion on all vehicles except the Corvette. Rochester’s new Quadrajet 4-barrel was Pontiac’s choice for its performance applications.

To be sure the new 4-barrel engines performed at least as well as the previous 360-hp Tri-Power engine, airflow was improved by reducing piston-to-valve angle from 20 to 14 degrees, and increasing valve diameters from 1.92/1.66 inches to 2.11/1.77 (intake/exhaust, respectively) in performance applications. Streamlined exhaust manifolds were used to improve flow, and the block bore diameter was increased .030 inch, which boosted displacement to 400 ci.


General Motors banned the use of multiple carburetion in 1967. In an attempt to maintain performance, Pontiac developed a new intake manifold and specified the new Rochester Quadrajet carburetor for its performance applications. Capable of flowing 750 cfm, it was an efficient design that was used well into the mid 1980s. (Photo Courtesy Tom DeMauro)

In addition to those changes, Pontiac completely redesigned the intake manifold using the 1960s Super Duty 4-barrel manifold as a template. The dual-plane design featured long, smoothly contoured runners to produce maximum torque at low speed. Though there was large push to cast the manifold in aluminum to save weight, cast iron was ultimately used to quell reliability concerns and maximize cold-weather operating characteristics.

The 421 was also slightly affected for 1967. As the full-size offerings grew in size, they required even more horsepower to maintain performance. Pontiac increased the 421’s bore to 4.12 inches, which produced 426.5 ci when combined with the 4-inch-stroke crank. To maintain its own identity in a market filled with the 426 Hemi and 427 Chevy, Pontiac’s was billed as a “428.”

The Round-Port Era
The Ram Air 400 available in the GTO and new Firebird was very much the same for 1968, and it came to be known as “Ram Air I” when a new Ram Air engine was brought to market in May 1968. The Ram Air II (R/A II) was rushed through the development process so Pontiac could give its customers a high-winding V-8. It borrowed technology from a new highperformance engine that Pontiac was developing for 1969, which contained some very unique pieces aimed at reaching its intended 6,000-rpm limit.

The R/A II featured all-new cylinder heads with redesigned round exhaust ports. The port work improved exhaust air-flow by about 10 percent over a comparable D-port, and the outlet shape was intended to make fitting tubular headers easier for racers. The valvetrain was comprised of specific heavy-duty components, and the new number-041 hydraulic-lifter cam was teamed with 1.5:1 rockers to produce .470 inch of valve lift. The combination was rated at 340 hp for the Firebird and 366 for the GTO.


The Ram Air II evolved into the Ram Air IV for 1969. New cylinder heads with larger intake ports, cast-aluminum intake manifold, and 1.65 rocker arms for the 041 cam were all intended to further improve the 400’s performance. Available in the GTO and Firebird, the 370-hp engine with nearly 10.5:1 compression was a stout performer. Such examples are highly coveted by collectors today.


The second-generation Firebird was introduced in 1970 and the Firebird Trans Am quickly became Pontiac’s premier performance model. With desirable rarity from a collector’s perspective, and capable of stout performance and excellent handling characteristics right off the showroom floor, the entire model line remains extremely popular today.

Two new performance engines were introduced for the 1969 Firebird and GTO, and both carried over into 1970 with minimal changes. Rated at 335 hp for the Firebird and 366 in the GTO, the 400 H.O., or Ram Air III (R/A III) as it was later known, utilized D-port cylinder heads and high-flow exhaust manifolds. Pontiac’s top engine option in 1969 and 1970 was its Ram Air IV (R/A IV), which had a solid 6,000-rpm operating limit. The intake-port roof of the round-port R/A IV cylinder head was raised 1/8 inch and the intake port volume was increased from 153 to 180 cc, which allowed it to operate at its intended limit.

The high-flow R/A IV cylinder heads were complemented by a new castaluminum 4-barrel intake manifold with enlarged runners and separate cast-iron heat crossover. The 041 camshaft teamed with 1.65:1 ratio rocker arms produced a gross valve lift of .520 inch the most ever used in any production Pontiac engine. The mill was rated at 345 hp for the Firebird and 370 hp for the GTO. Increased displacement was required to motivate GM’s full-size cars, which continued getting larger year after year. Pontiac’s 428 grew to 455 in 1970 by increasing bore size .030 inch and replacing the 4-inch-stroke crank with a 4.21-inch unit. The 455 H.O. was comparable to the previous year’s 428 H.O. and availability was limited to larger models and the GTO. The R/A III and R/A IV continued as Pontiac’s top engine options in the GTO and Firebird model lines.

Living with Low Compression
To regulate emissions, General Motors imposed a compression-ratio cap of 8.5:1 for the 1971 model year. That signaled the end for the R/A IV. Pontiac knew that increasing displacement meant similar horsepower could be attained at a lower RPM. By combining R/A IV–type components with the 455, Pontiac created the new 455 H.O.


To combat certain forms of tailpipe emissions and to keep insurance premiums in check, General Motors imposed a corporate compression ratio limit of 8.5:1 for 1971. Pontiac increased the displacement of its Ram Air IV to offset the loss of performance associated with lesser compression to produce that year’s 455 H.O. Rated at 335 hp, it used many Ram Air IV–type components and included revised round-port cylinder heads and an 068 camshaft.


An exhaust gas recirculation (EGR) valve is a vacuum-operated emissions control device located on the intake manifold of every Pontiac V-8 from 1973 forward. Its purpose is to allow metered amounts of exhaust gas to reenter the cylinders during certain operating conditions, limiting the formation of a specific pollutant. By design it’s nonfunctional at full throttle, so it shouldn’t have any effect on performance.


Even when forced to comply with emissions regulations, Pontiac shocked the industry when it released the Super Duty 455 in 1973. Featuring such components as a specially reinforced block, forged pistons and connecting rods, and new high-flow cylinder heads, the round-port engine was capable of running at 6,000 rpm. Availability was limited to the Firebird Formula and Trans Am in 1973 and 1974. Fewer than 1,300 were built during its two-year run.

Adhering to the imposed compression ratio limit, the 455 H.O. featured modified round-port R/A IV cylinder heads, a cast-aluminum intake manifold, and high-flow exhaust manifolds. The 068 camshaft was chosen to maximize low-end torque, and specific hydraulic lifters were used to effectively limit engine speed to no more than about 5,500 rpm, quelling warranty claims from overextended operation. The new engine carried a gross rating of 335 hp, and 305 hp at the new “net” rating, which more closely represented engine output when installed in a car. It remained Pontiac’s top engine option for 1972.

In response to more stringent exhaust emission standards, exhaust gas recirculation (EGR) was introduced for 1973. It consisted of a valve mounted on the intake manifold that allowed metered amounts of inert exhaust gas to re-enter the combustion chamber. The biggest news that year, however, was Pontiac’s newest performance engine, the Super Duty 455.

The Second Super Duty Era
The SD-455 was a max-performance effort designed to operate at 6,000 rpm. Additional material was added to the SD-455 block to increase overall rigidity, and it contained a provision for dry sump oiling at the rear. A nodular iron crankshaft with deep-rolled fillets was employed. It was retained by four-bolt main bearing caps. Specific forged-aluminum pistons were complemented by beautiful forged-steel connecting rods.


To improve the performance of its 301, Pontiac installed a turbocharger for the 1980 model year. It added more than 50 hp to the naturally aspirated 4-barrel mill, taking the total to around 200 hp. A number of special components were used to accommodate the added cylinder pressure that occurs under boost conditions. Availability was limited to the Firebird Formula and Trans Am.

The SD-455 cylinder heads’ intakeport volume was increased to 186 cc to allow for 6,000-rpm operation, and the exhaust ports were precisely modified to maximize flow. The intake port was so wide near the entrance that its sidewall actually broke into the adjacent pushrod guide passage, and a thin-wall steel sleeve was pressed in to seal it. Specific valvesprings and high-quality 2.11/1.77-inch valves were also used.

A new 800-cfm Quadrajet and a specific cast-iron intake manifold with enlarged runners were used with the SD-455. A 041-spec hydraulic camshaft was used throughout development and testing, lending to its 310-hp rating, but when it finally reached production in May 1973, a 744-spec cam was used to ward off emissions concerns, and the engine was subsequently rerated at 290 hp. Availability was limited to the Firebird model line. Only 295 SD-powered Firebirds were produced in 1973, and all were the 290 hp variety. An additional 1,000 Super Duty Firebirds were produced in 1974.

Emissions and Economy
New federal emission standards shook the industry during the 1975 model year. Pontiac utilized a single exhaust catalyst and a compression ratio of just 7.6:1 to ensure total compliance. High-ratio rear axle gearing was used to keep engine speed relatively low, which lessened emissions and improved fuel economy. Performance suffered and the 455 was emasculated to just 200 hp. A change that affected all 350 and 400 engines was the introduction of the “lighter” block castings in mid 1975. Pontiac knew that high-revving engines had become a distant memory, so in an attempt to shed overall vehicle weight, material was removed from low stress areas of the block. The blocks are reliable for normal duty applications, but should not be used in any high-performance effort.

Another significant change occurred in mid 1976. Pontiac eliminated the common harmonic balancer on most 350 and 400-ci engines backed by an automatic transmission. A crankshaft hub was used in its place and it served as an accessory drive and contained a top dead center (TDC) timing mark.

Emissions-Compliant Performance
The 455 was discontinued after 1976 and a high-performance 400 took its place in 1977. Rated at 200 hp, the new T/A 6.6 received a compression boost to 8:1 using 350-spec 6X cylinder heads, a unique camshaft, and specific carburetor and distributor settings.

With heavy emphasis placed on maximizing fuel economy, Pontiac developed a small-cube V-8 in a lightweight package to complement the downsized models it would introduce in the near future. The short-deck 301 was Pontiac’s answer to Chevy’s 305 and engineers had no intentions of it being a performance mill. The svelte block was filled with a crankshaft that had only one large counterweight at each end and cast connecting rods.

Revised camshaft timing and exhaust enhancements bumped the 400-ci T/A 6.6 to 220 hp for 1978, and durability issues arose with the lighter-weight 400 block. Pontiac revived a former 400 block casting specifically for 1978–1979 T/A 6.6 engines. These castings were as good as earlier units and can be identified by the “XX” cast into several locations on the block. Pontiac’s 350 was discontinued after the 1977 model year, and the last 400 blocks were cast on Thanksgiving weekend 1977 and stockpiled for use for the remainder of 1978. Several thousand were set aside for the 1979 Trans Am.

The End of an Era
The 301 was Pontiac’s only V-8 left in production by 1979. The T/A 6.6 was available for most of the model year, but once the supply of stockpiled 400s was exhausted, it signaled the end of the big Pontiac V-8.

A turbocharger was added to the 301 to give the 1980 Trans Am an injection of performance. With turbo boost limited to less than 10 pounds, the 301 was rated at around 200 hp in both 1980 and 1981. General Motors ceased Pontiac V-8 production in March 1981. It was the final chapter in a saga that started in 1955 and concluded after 14,624,886 engines were produced.

Pontiac Racing
Pontiac always maintained a performance image and a great number of hobbyists competed regularly with their Pontiacs in various stock and modified classes.

Some of those who have successfully campaigned Pontiacs during the 1950s, 1960s, and 1970s include Arnie Beswick, Truman Fields, Jim Hand, John Angeles and Pete McCarthy, Art Peterson, Nunzi Romano, Milt Schornack, Mickey Thompson, Jess Tyree, Jim Wangers, and Arlen Vanke. These guys drove some of the quickest Pontiacs to ever make a pass down the drag strip in their day.


Arnie Beswick drove a number of different Pontiacs during the 1960s and 1970s. Competing in classes ranging from Stock to Factory Experimental or others, Beswick capitalized on his Midwest roots and dressed like a farmer in an attempt to fool the competition, earning his trademark “Farmer” nickname. He remains quite active and often attends various major Pontiac show and/or race events across the country. He almost always has one of his Pontiacs with him.


Mickey Thompson was so serious about Pontiac performance during the early 1960s that he took it upon himself to develop and produce a specific cylinder head with a hemispherically shaped combustion chamber, which was sold by his Long Beach, California–based Mickey Thompson Equipment Company. A complete line of accessories was also available, which included pistons, valve covers, and intake manifolds. This particular engine is owned by hobbyist Jack Gifford.


According to vintage Micky Thompson (M/T) sales literature, the Pontiac hemi head allowed the use of much larger valves to improve airflow and placed the spark plug near the center of the combustion chamber to promote a more consistent burn. Thompson claimed an increase of more than 100 hp was possible when compared to modified Pontiac heads.


Kauffman Racing Equipment produces a wide variety of heavy-duty components for those wishing to compete at the top levels. This 535-inch engine features an aluminum block, canted-valve cylinder heads, and dual carburetors. It generates more than 1,100 hp and has run the quarter-mile in as quick as 7.20 seconds at more than 190 mph in a 2,200-pound race car with a Pontiac GXP body.


Butler Performance has gained a reputation as a premier Pontiac engine builder providing hobbyists with potent combinations ranging from dedicated street engines to max-performance boosted V-8s. Rodney Butler’s 482-ci Pontiac features twin turbochargers that provide 40 pounds of boost. The 2,880-hp beast has propelled his 2,700-pound 1963 LeMans to a quarter-mile best of 6.27 at 228 mph. (Photo Courtesy Don Keefe)

Several companies specialized in improving Pontiac performance, including Baldwin-Motion, H-O Racing, Leader Automotive, Nunzi’s Automotive, and Royal Pontiac. These companies, and a few others, can be credited with keeping Pontiac V-8 performance flame alive during the smog-era and the years immediately following its discontinuance. They paved the way for today’s aftermarket companies, which produce the components that give new meaning to the term max-performance Pontiac V-8.

Written by Rocky Rotella and Posted with Permission of CarTechBooks

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Filed Under: Pontiac Engines, Pontiac Performance, Pontiac Tech Tips, Pontiac V8s



I found this Pontiac V8 engine overview just a while ago Richard.
Most is correct.
The 1968 Ram Air II - 2 engine pictured is actually a 1970 Pontiac Ram Air IV 400ci Engined GTO .
Often mistakes in Pontiac Articles.
The 1968 Pontiac Ram Air 2 II 400 used a cast iron intake manifold. Not aluminum.

I am going to start a new thread on Pontiac V8 engine ID for You.

I tried to find a vintage HO- Racing article on Pontiac V8's written back in 1985.
It does not exist on the internet, was never scanned in.
I have the article in a magazine somewhere.
Recall and memorized it when I was 17 years old.


solid fixture here in the forum
Staff member
455 Is Casted on the outside of the Block next to the motor mounts pads.

I know, that's how I knew their 455 - wasn't a 455.

There was no crappy 455 built.
Ditto for 400 & 350 Pontiac too.. . . . . . . . . . .See what I can put together tonight to help you.

I never said any were crappy, I just want one of the better performers out of most 455s. Hell, I really would like a real HO engine, but I have no desire to pay a ridiculous premium when I don't have the original car for that motor.