Part 2: ’68 to ’73
- 303 and 366 race engines
- 366 proposed production engine
- SD-455 production engine
While Pontiac was showing off the new ’69 Trans Am to the press at Riverside International
In Part I, we introduced you to some of the dedicated engine engineers and scientists who worked on moving Pontiac out of the world of the Straight 6 and straight 8 and into the future of the Pontiac V-8.
For this installment, Pontiac Special Projects Engineer Herb Adams shares how he and his team developed the 303ci Trans-Am series and 366ci NASCAR Grand Am series race engines, the proposed 366ci production engine, and the SD-455 production engine.
“I was fortunate to be the team leader in the development of these engines,” Adams says. “Pontiac Assistant Chief Engineer Bill Collins assigned Special Projects the job of developing a race engine for use in the SCCA Trans-Am series. It all started after racer Jerry Titus came to Pontiac and asked us to design and deliver a Pontiac 5.0-liter engine for his race car that could compete against the 475hp Chevy small-block race engines. Since Pontiac was not allowed to directly support racing due to the 1963 corporate edict, our non-descript department, named Special Projects, allowed us to work under the radar on high-performance racing and production-engine development.”
Pontiac Special Projects Engineer Herb Adams leads H.B. Bailey and Tiny Lund through a tur
What follows are Herb’s recollections of Special Projects teammates Tom Nell and Jeff Young, and their contributions to Pontiac’s high-performance V-8 programs.
Title: Assistant Race-Engine Engineer, Pontiac V-8 Power Development
Accomplishments: 303ci direct-drive dry-sump, SD-455 clean-block test, reverse manual-valvebody automatic transmission
Tom Nell started at Pontiac in June 1959 in chassis drafting, where he remained for three months. He then moved on to experimental engineering. There, under the direction of Pontiac’s senior project engineers, he wrote work orders to Pontiac’s repair shop and dyno lab to test experimental engine components, and then oversaw and evaluated the testing results.
I don’t recall the first time I met Tom, but I sure remember our first road trip together. I had graduated from General Motors Institute, and he and I were testing Pontiac’s factory air-conditioning systems in southern Texas. There was other Pontiac staff with us, and we all had two-way radios. I remember drivers from the end of the line radioing him and saying, “Hey, Tom, slow down.” That’s when I knew Tom was into making Pontiacs go fast.
He was directly involved in the Super Duty program for approximately one month before the 1963 GM racing ban. He observed that the dual-quad, high-rise plenum manifold, which was shipped in the trunk of the ’63 SD cars, produced no throttle response on hard launches. He took the initiative to fix the problem. “I was getting a lot of complaints about it from the drag racers,” Tom says. Carb manufacturer Carter and Pontiac agreed that the fix was necessary, and all of the racers who received the original four-barrel carbs were sent new ones at no cost to them.
Sometime prior to February 1963, Tom procured a dead 421-SD under Pontiac’s employee-purchase program, rebuilt it, and supplied it to Cam Gagliardi and Gil Kramer, who put it in a ’53 Studebaker. In the NASCAR Modified 250-mile race (Permatex 250) on February 23, 1963, it was clocked at 163 mph, qualified on the outside pole, led 74 of 100 laps, and won the race. The next year, Tom invited me to come to Daytona to be a crewmember for him and the Pontiac-powered Studebaker team, which I did.
Before long, most of Pontiac’s engineering staff knew Tom was a racer at heart, and not just on superspeedways. Pontiac was forbidden from being involved in professional racing, but Tom was at dragstrips every weekend helping out the Pontiac racers. That’s how he met legendary Pontiac drag racer Arnie “The Farmer” Beswick, and it’s how Tom designed the first reverse manual-valvebody Turbo 400 transmission.
With the “Transaction Tempest” in the background, shown at Waterford Hills in 1970 are Joh
From 1965 to 1968, Tom was the project engineer in charge of Pontiac V-8 power development in the Pontiac dyno lab. He saw the birth of the first Ram Air engine and the Ram Air II, III, IV, and V engines.
The 303ci Trans-Am Series Race Engine
One of Tom’s first tasks in Special Projects was to order a tall-deck 400 four-bolt main-block (all Pontiac production 400s were tall-deck) and have it delivered to Pontiac Engineering’s machine shop, where the machinists prepped it to his specifications (0.030-overbore). Tom had connections with Moldex and asked them to manufacture the 2.84-inch-stroke cranks. He supplied the company with marked blueprints of the Pontiac 400 crank noting the changes he needed. He also arranged for Carrillo to build the 7.08-inch rods for the experimental engine.
Tom’s knowledge of GM’s Turbo 400 led to his invention of the 303 race engine’s dry-sump oil pump. He took the internal gear pump from the Turbo 400, and figured out how to make it the key component in a cam-gear-driven oiling system. His direct-drive oil pump was a huge improvement over traditional belt-driven systems.
His contributions made it possible for us to reach competitive power levels quickly with the 303. Jeff Young recalls overseeing a dyno session in 1970 or 1971 that produced numbers of 475 hp at 8,200 rpm. Though we don’t have that chart, Tom was able to provide one from March 15, 1972, that shows 453 hp at 7,500 rpm and 355 lb-ft at 6,000 rpm.
We didn’t want the professional racers to get all the glory or have all the fun with the 303. When we installed a 303 into my wife’s old ’64 Tempest and went Trans-Am series racing in 1970, Jeff and Tom shared responsibility for the engine, transmission, driveshaft, and rearend assembly.
(Note: Though not part of Special Projects’ original mission, I credit Tom for getting the 303 in the Firebirds campaigned by H.B Bailey, Buck Baker, Tiny Lund, and other NASCAR racers in the Grand-Am series.)
The 366ci Race Engine
Likely sometime in late 1970 or early 1971, Tom built the first Pontiac 366 engines for NASCAR. He started with short-deck 303 blocks cast by Pontiac, and then ordered 3.375-inch-stroke Moldex cranks, 6.08-inch Carrillo connecting rods, and 4.15-inch pistons and used modified R/A-IV heads. He directed its power development in the dyno lab, and it produced 575 hp on a PMD dyno. This was 100 hp more than the 303, so I figured we must have hit the sweet spot for the Pontiac V-8.
Special Projects Engineer Jeff Young recalls higher-horsepower numbers, but this dyno shee
From Tom’s short time in the 421-SD program, he recalled that a common cause of premature failure in those engines was debris left over from the block-casting process that made its way back into the bearings. He wasn’t going to have any of that in the SD-455 engines.
Tom explains: “As a quality-control test, Pontiac engines were randomly pulled off the engine-assembly line once they were completed, and test-run in at a location at the end of the assembly line that we called the merry-go-round. I ordered the assemblers to transfer every SD-455 to the merry-go-round, break it in, remove the oil pan, clean out all casting debris, bolt it back onto the bottom of the block, and refill it with fresh oil.”
Title: Project Engineer and Senior Project Engineer
Accomplishment: Horsepower development on the 303 Trans Am series and the 366 NASCAR engines; development and design of the SD-455
Pontiac Special Projects’ team members’ ’73 Grand Am, powered by a Pontiac 366 engine, pos
Jeff joined Pontiac in 1963 as a General Motors Institute (GMI) student, and was sponsored by Pontiac Engineering. “I wanted into the high-performance game,” Jeff recalls. “One of my interviews allowed me to take a ride in a prototype GTO, which was a ’63 LeMans coupe with a 389 Tri-Power and a four-speed, and a full frame added.”
His first assignment was in the sheetmetal stamping plant, where he worked on the design of stamping dyes and familiarized himself with the stamping process. His next assignment sent him to the Pontiac foundry, where he worked in pattern and mold design.
Jeff’s GMI work assignment moved to Pontiac Product Engineering in 1966, and he worked in the engine and chassis experimental departments for several months. I met Jeff at the Proving Grounds and asked him to join Advanced Design, where he got to work designing a hemispherical head for the Pontiac Hemi 6 engine.
“One of my first assignments was to do basic airflow research aimed at optimizing cylinder-port design,” Jeff remembers. “The results of that development showed that there was tremendous potential for improving airflow within the confines of a production cylinder head.” As I recall, we credit Jeff with fine-tuning Pontiac’s first high-performance flow bench.
In 1968, Jeff left Pontiac to study at Massachusetts Institute of Technology (MIT), where he majored in combustion engines and earned a master of science degree in Mechanical Engineering. Pontiac wanted him to do his thesis on camshaft design for exhaust emissions (a subject he later researched for Pontiac). Instead, his thesis was “Using the Convective Heat Transfer Co-efficient of Cylinder Gases as an Indicator of Flame Propagation Potential [Turbulence vs. Flame Speed].”
I stayed in touch with Jeff and told him I’d like for him to be on Special Projects when he returned to Pontiac after graduation. That was in June 1969, and he took over for Leo Hilke as project engineer on the Pontiac 303 Trans-Am series racing engine.
Up until that point, the 303 produced a less-than-competitive 375 hp. Jeff theorized that Pontiac’s use of a Ford-style tunnel-port on the short-deck 303 was the hindrance to horsepower advancement. Tom and I were already considering dropping further development of the tunnel-port, and Jeff’s airflow research on port design supported this. When he told us he didn’t like the tunnel-port either, it was gone.
“Tom had already done enough dyno work with the Ram Air IV heads to know that they had all the potential we needed for the 303,” Jeff explains. “I sent three pairs of Ram Air IV heads to three different porting specialists, two in Southern California and one in Florida. I told them, ‘Do the best job you can to maximize the airflow on these heads.’ One of the three companies, Air Flow Research, contoured the pocket area underneath the intake and exhaust valve heads. The company also opened up the ports around the pushrod area. The result was a dramatic improvement in airflow.”
Jeff monitored the individual air/fuel ratio of each cylinder and observed there was fuel puddling on the floor of the intake manifold, which caused some cylinders to be rich and others lean. “By epoxying strips of 1⁄8-inch aluminum to the floor of the plenum area to function as flow directors, Jeff was able to balance the air/fuel ratio equally to all cylinders.
He did extensive development work in header design, and came up with a 32-inch-long x 2-inch-diameter equal-length header tube. “By equalizing the length of the primary exhaust tubes for all cylinders, we produced good power over a wide rpm band,” he says.
Jeff also made it much simpler for us to evaluate camshaft grinds, and find the ones that would give us the most power for the racetrack. He did it by adapting a generic statistical-analysis program used by GM research for optimizing various parameters of system development, and specifically set it up for camshaft development. “It shortened the number of dyno runs from 27 to 9 (using a different cam grind on each test), while not giving up statistical significance of the results,” Jeff says. In the process, he scientifically confirmed that exhaust closing was the most important parameter of a camshaft’s profile. (The other three parameters are intake opening, intake closing, and exhaust opening.) The result: Jeff’s contributions to the 303 produced a gain of 100 horsepower.
When we took it upon ourselves to build and race a ’71 Firebird to show how good the Pontiac 303 really was, Tom was responsible for the engine, transmission, driveshaft, and rear-end assembly.
On May 29, 1972, we took Second Place at the SCCA Trans-Am race at Bryar Motorsports Park in Loudon, New Hampshire. On June 4, 1972, we led all 75 laps at the SCCA Trans Am race at Mid Ohio and won First Place. On July 15, 1972, we took Second Place at the SCCA Trans-Am race at Road America in Elkhart Lake, Wisconsin.
The SD-455 engine
After wrapping up 303ci development, Jeff began working on the non-standard production parts for the SD-455.
A ’74 SD-455 engine moves along the assembly line.
“We transferred Tom’s knowledge of the 421-SD to the SD-455,” Jeff says. “We beefed up the main bearing webs on the block, based upon his experience. Beyond that, virtually every major component of the SD-455: the block, crank, connecting rods, pistons, and heads, cam, cam-gear, fasteners, bearings, and Holley 4150-style aluminum intake manifolds (later dropped for a cast-iron intake and a Q-jet) were different than Pontiac’s production 455s.”
Jeff designed the SD-455 cylinder heads from scratch using the basic bolt patterns of the Pontiac’s production V-8 head, but with intake and exhaust port layout based upon the airflow research he had done. “The pressed-in, thin-wall steel pushrod tubes, which were Herb’s idea to prevent any significant intrusion into the intake port,” he says.
We had one inherent problem with developing the SD-455 engine-block and crank setup,” Jeff recalls. “The 3.25-inch main bearings from the production 455 cranks were working against us. It was centrifugal force. We had to develop a block that used 3.00-inch main bearings.” [Regardless, production SD-455 engines used 3.25-inch mains.]
In Part I, I explained production rods were durability-rated to 4,500 rpm at wide-open throttle for 100 hours non-stop, and Jeff argued that the SD-455 connecting rods needed to be a clean-sheet design, so he designed them. Thanks to his efforts, SD-455 forged rods were durability rated to 160,000 psi. That’s more than two times the strength level of the production cast-iron rods.
How did he come up with the perfect connecting rod in the days before computer-aided design (CAD) and finite-element analysis (FEA)? “We used two techniques to observe high-stress areas of our prototype connecting rod forgings: the brittle stress-coat technique and strain gauges,” Jeff says. “The brittle stress-coat points out the areas of high concentration of stress, and the strain gauges (any particular connecting rod we tested had up to eight of them installed) quantified the stress level, as measured in psi. I worked those connecting-rod contours until I eliminated all of its stress points, which could lead to engine failure.”
The 366 race engine
Neither I nor the other Special Projects members recall a clear delineation between when one engine program ended and the next started. “They were concurrent and parallel,” Jeff says.
Jeff fast-tracked 366 race engine development because it was based wholly on the short-deck 303 engine. “We spent time on additional camshaft and exhaust tuning,” Jeff says. He also performed extensive research on cylinder-head-gasket sealing and developed a package that we had reasonable confidence in.
In April 1971, Jeff took his turnkey 366 dyno-development engine, put it in a company truck, and had it delivered to Nichels Engineering in Griffith, Indiana. “I was there for the engine unloading and watched the beginning of the engine’s installation onto Nichels’ dyno,” Jeff says. “I remember getting a call from Nichels saying, ‘Do you know what that engine of yours puts out?’ I recall it was producing 520 gross horsepower.” NASCAR racer David Pearson—driving a ’71 GTO with this specific 366 installed—broke the qualifying track record at Talladega International Speedway in May 1971.
Here is Tom Nell, circa 2005, from “Latin Squared Derived Camshafts Revealed” in High Perf
Jeff was the last of my Special Projects teammates to remain employed by Pontiac. He was banned from any activities relating to high performance, and transferred to production-engine development where he worked on exhaust-emissions development for Pontiac production V-8s. He left Pontiac in 1976.
Title: Assistant Chief Engineer
Accomplishment: 366 Street engine proposal
In Part 1 of this story, I called Russ Gee one of the pioneers of the Pontiac V-8, and for good reason. In 1957, Pontiac General Manager Bunkie Knudsen and Pontiac Chief Engineer Pete Estes made him the engineer in charge of Pontiac’s stock-car racing program.
In 1968, Russ headed Pontiac’s dyno lab. After I received the assignment to develop the Pontiac 303, I went to Russ and asked him, “Can we use a dyno?”
Russ gave us exclusive use of Pontiac Dyno Room No. 2. Why? I think Russ clearly saw the connection between Pontiac’s high-performance engine programs and its dominance in motorsports, and that the adage “Win on Sunday, sell on Monday,” was true.
Russ didn’t try to micromanage us. I don’t ever recall him trying to force his ideas upon us while we were developing the 303ci race engine. He certainly wasn’t aligned with the authoritative style of Pontiac Motor Engineer Mark Frank, who I spoke about in Part 1 of this story.
The production 366 engine
I showed the 366 race engine’s dyno results to Russ, and he asked if we thought the 366 would translate into a good production engine. We built a production-proposal 366 engine using a short-deck 303 block, Ram Air IV heads, and cast-iron exhaust manifolds. (We tickled the cam a little but otherwise used parts-bin engine components.)
Here’s Jeff Young in 2012 with a friend’s ’68 Firebird convertible…
Tom dyno-tested the street 366, and it produced almost the same torque as a stock 400 with more horsepower. In our minds, the Pontiac 366 was better than the small-block Chevy, in that it was about the same weight and size as it, but produced more horsepower.
Russ agreed. He recognized the opportunity to retire the Pontiac 350 and 400, and replace both of them with the 366 as the large-volume production engine. “The 400 was one of my favorite engines, but I think there was a downsize campaign going on in the entire automobile industry,” Russ recalls. “That could have given the 366 the window of opportunity it needed to become Pontiac’s bread-and-butter engine.”
Russ and I made several proposals to Pontiac management to get approval to work on the project. Our first stop was to Pontiac Chief Engineer Steve Malone. I don’t think Steve even understood what we were proposing, but he allowed us to show it to Pontiac General Manager Jim McDonald.
McDonald, after hearing us out, told us how wonderful our presentation was. I asked him if he would authorize us to proceed with the project. “You expect me to make a decision without even studying the idea?” he asked.
Herb Adams today showing off a scale-model of his Contessa sports car’s frame at a recent
Unlike John DeLorean, who preceded him and would give a thumbs-up or a thumbs-down and that was that, McDonald subjected what Special Projects believed was the best idea in Pontiac V-8 history to a slow death. He sent me to the engine plant and its leaders disbelieved that a 366 made more power than a 400. Then he sent me to the sales department, which uttered the same disbelief. In my opinion, if DeLorean was still Pontiac general manager at that time, there’s no doubt in my mind that the Pontiac 366 would have changed the course of Pontiac V-8 history by powering all of the Division’s production cars from ’73 onward.
I credit Russ with another idea: Why not take what we learned on the 303 and 366 race engines and apply them to a high-performance 455? By this time, the use of unleaded fuel and insurance rates had put an end to the horsepower race, but if Pontiac could have the first high-performance engine with 9.0:1 compression it would help to maintain the brand’s image and keep the Trans Am from becoming a decal package.
Russ stayed with Pontiac until 1979, and then transferred to Chevrolet’s high-performance team. While at Chevy, with authority over Pontiac regarding powertrain, Russ issued the corporate order to turbocharge the Trans Ams and Firebird for ’80 and ’81.
In the fall of 1972, we sold our ’71 Firebird racecar and bought a body-in-white ’73 Grand Am, which we fitted with a 366 race engine and prepared to race in the 1973 NASCAR Winston Cup series.
Near the end of 1972, Pontiac management disbanded Special Projects entirely. “The official reason was that Pontiac needed to put all of its engineering efforts on upcoming emissions requirements, which were to be implemented in March 1973,” Tom recalls. Luckily, when we were shut down, the SD-455 engine was ready for production.
Despite being disbanded, we campaigned the Grand Am at the Winston Western 500 on January 23, 1973. We started at 16 and ended the race in 15th place. The next month we took the Grand Am to Daytona. After enduring more tech-inspector scrutiny than we had at any race up to that date, NASCAR brass allowed us to enter the Twin 125 Qualifying Race on February 15. We started in 35th place and did not finish.
While at Daytona, I learned that the then-Pontiac PR director made a personal telephone call to Bill France Sr. and told him Pontiac did not want our car to compete in the Daytona 500. So when I returned to Pontiac after the race, I tendered my resignation. Shortly thereafter, I saw Tom in the hallway at work, and he told me he had put in his resignation, too. Though we didn’t plan our resignations together, we were both disappointed with Pontiac management.
My final staff meeting at Pontiac was in the spring of 1973 when Russ Gee and I were required to answer the interrogations from Pontiac General Manager Martin Caserio, who was determined to learn who was responsible for authorizing the SD-455 program. Caserio demanded a verbal report from all of us in the meeting. The engine-assembly plant told him it had parts to build 600 engines. The Sales Department told him it had 600 orders for the SD-455 engine, but Pontiac management was holding back on its release. Since I had already resigned from my job at Pontiac, I told him he had 600 engines in parts and 600 orders—why not build the engines and sell them? It was my last official contribution to the Pontiac V-8.