History of the Gen III LS1 V-8 Engine • LS Engine DIY (original) (raw)

There are a few acts of creation an automobile company must be great at if it plans on being successful in the car business. These actions usually include being able to:

  1. Design and build visually pleasing, high quality, and durable automobile bodies/chassis.
  2. Design and build powerful, reliable, and efficient powertrains.
  3. Refine the components and systems noted above into a smooth-riding, predictably handling machine.

General Motors has excelled at many of these actions over the years, but in the powertrain department, their track record has been truly impressive. The amount of elegantly simple, reliable, fuel-efficient, and powerful engines that have propelled Generral Motors vehicles through its history is simply unmatched. Of those engines, the Chevrolet small-block V-8, of which the Gen III LS1 V-8 engines discussed in this book are a derivative, are considered the pinnacle by most car enthusiasts.

Luckily for all automotive enthusiasts, GM has used the Gen III LS1 V-8 to power numerous visually pleasing, good handling cars and trucks. How an engine of this caliber comes to life is a story few would probably ever know. But in the following article, you will find out how something as complex as an engine is created from a clean sheet of paper to be built in quantities in excess of 8,000 per day.

This tech tip is from the full book, HOW TO BUILD HIGH-PERFORMANCE CHEVY LS1/LS6 V-8S.

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Small-Blocks: Gen I/II/III

The original version of the small block, what is now considered the Gen I (first generation), was used to power GM vehicles, mostly Chevrolets, from 1955 to 1991 — almost 40 years. The Gen II, which came in two main versions, the LT1 and then later the LT4 (LT1 and LT4 are their regular production order (RPO) numbers), powered vehicles from 1992 to 1997. Gen II did not live up to the Gen I legacy in many ways and was struggling to meet the emissions and weight requirements that loomed in its future. These were major reasons for it being superseded by the radically different Gen III V-8 in 1997.

The Gen III V-8 is simply a work of art. This is clear when you think about how much it is capable of relative to its straightforward design. This is like many great designs — they don’t seem that impressive at first, but the more you look at them and work with them, you realize the subtle detail and capability of every aspect.

Gen I and II V-8s powered GM vehicles for over 40 years, so they are timeless designs that are revered by the original equipment manufacturers (OEM) and aftermarket industry. It was obvious to the GM Powertrain leadership in the early 1990s that an entirely new design was needed to meet the customer, government, and company needs of the future.

The small-block Gen III LS1 V-8 is the son the Gen I didn’t have. It is the most powerful, efficient, durable, and yet physically simple gasoline internal combustion V-8 engine ever built for production vehicles. Without a doubt, by creating and selling the Gen III LS1 V- 8, GM pulled the 50-year legacy of small-block V-8s from the ashes and created an entirely new future for this beloved engine family.

Thumbs-Up for the Gen III

On a warm, sunny day in May 1992, a blind comparison test was performed by General Motors executives on a massive pavement area called Black Lake, deep within the secretive GM Milford Proving Grounds outside of Detroit, Michigan. The conclusions drawn from this test would change the course of history for General Motors Powertrain, its customers, and the automobile industry.

At the time, the automotive business was ferociously arguing the merits of building complex, seemingly high-tech dual overhead cam (DOHC) engines, as opposed to simple, seemingly low-tech pushrod engines. This hands-on comparison by the execs was to put the debate to a seat-of-the-pants test and allow the leaders of GM to decide the course for the future of GM Powertrain.

The Gen III V-8 engine was voted Wards’ Engine of the Year in 1997 and Ed Koerner (right) accepted on behalf of the entire Gen III V-8 team. That a “new” pushrod engine won this award was almost unbelievable to the design team.

The executive leadership of GM would drive pairs of similar-appearing vehicles and compare how each vehicle felt — not knowing what type of engine was powering the vehicles. Of most interest to readers of this book were two black Corvettes parked at the end of the lineup. One ’Vette was fitted with a 330- hp early version of the LT4 Gen II V-8 pushrod engine. The other was equipped with the ZR1-spec, Lotus designed, all-aluminum, DOHC LT5 engine. Both vehicles were equipped with automatic transmissions. Both were fully integrated for their specific powerplants to give a real-world experience to the executives.

The Gen III V-8 has exceeded all expectations both inside GM and in the hot rod community. Probably the most exciting aspect of the Gen III V-8 is that the capability of this engine architecture is still being discovered both in the Corvette chassis (shown) and in other GM vehicles it powers. Look for amazing power production and durability from this engine architecture in the years to come as GM and the aftermarket create more variations.

Back in late 1991 and early 1992, some early drawings were created for what the Gen III V-8 might look like once finished. This early drawing depicted how the front and rear engine covers would eliminate the need for the Gen I/II V-8 engine screw-in and press-in plugs. The final Gen III V-8 design looks very similar to this.

The results surprised even the most ardent supporters of the pushrod architecture. The executives couldn’t get over how one of the Corvettes pulled from the moment they pressed on the throttle — the surge, the thrust, the torque.

In contrast, they commented on how the engine in the other ’Vette seemed to take a moment to “wind up” before pushing them back in the seat. This vehicle required more precision and planning when driving fast to keep the engine up in the RPM band where the power was.

As the day went on, executive after executive came to the same conclusion. After all had tested the vehicles, the hoods were raised. To anyone who has driven or ridden in a vehicle powered by a 300+ hp small-block Chevy V-8, it comes as no surprise that the Corvette the executives liked was powered by the Gen II pushrod V-8.

From then on, the course for GM’s V-8 powertrain was set. The world’s finest pushrod V-8 would be created to power the most profitable vehicle’s in the General Motors fleet. This was the birth of the Gen III small-block V-8.

The initial driving force behind what would become the Gen III V-8 engine was Tom Stephens, then Executive Director of GM Powertrain. In late 1991, Stephens asked a few of his trusted engineers in the Advanced Engineering area of the GM Powertrain building off Joslyn Avenue in Pontiac, Michigan, to quietly work up the basic structure of a completely redesigned multi-use pushrod V-8. Two of those asked to do that initial work, Alan Hayman and Jim Mazzola, discuss their experiences later in this chapter.

Like much of the GM leadership, Stephens knew the Flint small-block V-8 engine plant and the tooling inside, where the Gen I and II V-8 had been produced for over 43 years, was well beyond its lifecycle. Since all new tooling needed to be created anyway, Stephens decided to roll the dice. He intended to propose to the GM brass that an entirely new small-block V-8 be built in entirely new plants with entirely new tooling. The key to his pitch to the GM leadership was that he would not exceed the estimated $1.2 billion set aside to revamp the Gen II V-8. On top of that, he would commit that the completely new Gen III V-8 would also exceed the goals set for the revamp of the Gen II V-8.

This other early drawing shows how the oil pan would be a cast-aluminum structural component to add stiffness to the engine/transmission combination. This helps the vehicle engineers to minimize low-frequency vehicle vibrations. Also, the Gen III block, heads, and oil pan were to incorporate many of the bosses required to mount the accessory components. You can see this here in the oil-pan-mounted air conditioning compressor. The cutaway for the A/C compressor didn’t make the cut, but the compressor does mount directly to the block/oil pan.

With this proposal, Stephens and his team had to produce an engine with impeccable credentials. Those credentials included producing a small-block V-8 engine that would:

Stephens used many of the original pushrod V-8 ideas proposed by the Advanced Engineering Group in his pitch to get the program okayed. Proposing to show improvement on an engine doesn’t sound like such a big promise, but remember, Stephens was betting to improve on the small-block Chevy — an international icon in performance V-8s!

Team Owner and Head Coach

The Gen III V-8 program originally began with the Gen II Chief Engineer, Anil Kulkarni, running the Gen III program for Stephens. Kulkarni had strong opinions about many aspects of the Gen III project that differed from Stephens’s vision — which lead to him moving on to other responsibilities early in the project.

Stephens then brought in Ed Koerner, a GM Powertrain small-block V-8 leadership veteran and former National Hot Rod Association (NHRA) record holder in drag racing, to run the program. Koerner, who had been the Chief Engineer for all the existing small-block V-8 engines, was made the Chief Engineer on the Gen III LS1 V-8 development project.

Later in this chapter, you will see that the original LS1 vehicle integration team had a hell of a time getting the oiling system to handle continuous side loads. It’s easy to see why — the crankshaft-to-oil-pan floor clearance. Can you say tight!? Probably more amazing is the fact that the GM Powertrain engineers figured out how to control the oil well enough with a short-sump oil pan and wet-sump oiling system to keep things pressurized under all driving conditions.

Later in this chapter, you will see that the original LS1 vehicle integration team had a hell of a time getting the oiling system to handle continuous side loads. It’s easy to see why — the crankshaft-to-oil-pan floor clearance. Can you say tight!? Probably more amazing is the fact that the GM Powertrain engineers figured out how to control the oil well enough with a short-sump oil pan and wet-sump oiling system to keep things pressurized under all driving conditions.

This is one of the first truck Vortec Gen III V-8s ever built. Notice the word “Beta” on the valve cover. This means the components on this engine were built on short-run, prototype GM Powertrain beta tooling to test the initial design of the engine. Beta component testing is the first running test for any engine design and is performed to avoid basic architecture shortcomings before initiating production-type gamma tooling. This tooling is used to build the 50 or more development engines needed to do the dyno and vehicle testing to fully validate an engine’s architecture.

Many of the initial team members interviewed for this chapter referred to Stephens and Koerner in pro football terms — Stephens was like the team owner, running interference on a corporate level, and Koerner played the role of the trusted and empowered head coach, running the plays on the field. Koerner was responsible for creating the production vision for the engine and assembling the all-star design team. The people Koerner chose to create the Gen III and the direction he provided throughout their journey are major reasons why the Gen III is the incredible V-8 engine it is. Clearly, a major factor in the Gen III V-8’s success was the trust between Stephens and Koerner, which allowed each to do what was needed to produce a quality product.

The dramatically new C5 ’97 Corvette, with its new hydro-formed frame rails, rear-mounted transmission, improved single length arm (SLA) independent suspension, Gen III V-8 LS1 engine, and redesigned body really wowed the crowds during its intro. The looks and performance of the C5 set the LS1 Gen III V-8 engine in the minds and hearts of auto enthusiasts everywhere.

The dramatic differences between the Gen I/II (top of each photo) and the Gen III head design (bottom of each photo) are easily seen in these photos. Simply put, the Gen III cylinder head is superior in every way to the Gen I/II head — port flow, chamber charge motion, packaging, temperature management, weight, oil control, and valvetrain stability.

Coaching Clarity

Koerner, who is now the Executive Vice President of GM Powertrain Engineering, is a gearhead who counts many successful racers and performance-aftermarket engine-parts-builders as friends from his days in the NHRA. His office, adorned with exploded view images of the Gen III and performance vehicles, tells anyone who enters that this is a man passionate about GM performance.

In person, Koerner, who is quick with an unassuming smile, can rattle off the vision for the Gen III V-8 as though he just woke up in the middle of the night with it.

“We wanted something of simple elegance. An engine that incorporated refined race technology. The block needed to be cast of either aluminum or iron, have six-bolt mains and have head bolts that pulled from the bottom of the block. It needed to be set up for an internally balanced crank, have a raised cam for crank counterweight clearance, and use bigger cam bearings than the Gen I and II. The bore spacing and external configuration also needed to take into account the fact that this engine was intended to be used in rear-wheel and front-wheel-drive applications.

“The heads needed to have replicated ports and a rolled valve angle (from the Gen I/II’s 23 degrees to 15 degrees) to optimize injection and combustion chamber motion because of our power and emission requirements. The valvetrain would have an in-line geometry, roller rockers and roller followers, a gerotor oil pump driven off the nose of the crank to eliminate the old camshaft-driven oil pump drive, and other improvements in an effort to reduce friction and flex wherever possible. Oil control would limit any wasted pumping losses.

“For manufacturing simplicity, we’d eliminate the plugs at the back of the block by adding a rear cover and have a plastic, integrated intake manifold built using a lost core process to create smooth internal transitions for maximum airflow. The engine would have an electronic throttle control (which appeared on the ’97 Corvette) to provide power management.

Famed GM cylinder head designer, Ron Sperry, developed the original Gen III V-8 heads (foreground). Ken Sperry’s team developed the ports and combustion chamber. The Sperrys have been called on for input into just about any important production or racing GM port and chamber design over at least the last 20 years – like the C5R Gen III racing head in the background. For the Gen III, they used every capability GM has: supercomputer flow modeling, prototype component construction, hydra single-cylinder test engines, flow benches, and dynamometers.

“Oh, and the same basic architecture had to satisfy the needs of everything from the Corvette to all the full-size trucks — which meant multiple cubic-inch sizes which ended up being 4.8, 5.3, 5.7 and 6.0 liters and various power production levels.”

This excerpt of Koerner’s recollection came with no prepared notes or moment of reflection. It just seemed to pour out of him, which shows how clear his vision for the Gen III was and still is — some 10 years after he began the project.

The Dream Team

A vision without having some great players is merely a dream, and Stephens and Koerner understood that. The initial team of seven engineers, which Koerner called, “The Super Six,” included Ron Sperry, Bill Compton, Brian Kaminski, Jon Lewis, Stan Turek, Don Weiderhold, and half-timer Dave Wandel. As GM cylinder head guru Sperry commented later, “Okay, that’s 6.5, but we were considered six full-timers.”

This cross section comparison of the production GM LS1, racing-only C5R, and 18-degree cylinder heads gives an idea of the advanced nature of the Gen III LS1 head design. Notice the 15-degree Gen III valve angle on the LS1 head vs. the 18-degree valve angle of the GM Racing NASCAR SB2 head and the 12-degree valve angle of the C5R Corvette racing head. Also, you can see the dramatic raised-port shape and valvetrain mount on the C5R head, the small chamber on the C5R and 18-degree head vs. the LS1 head. (Special thanks to Katech Engineering for this illustration)

The team continued to grow in size until the launch of the engine in 1996, when there were well over 100 engineers and support staff. Many of the initial team members assembled to create the Gen III V-8 have dedicated their lives to being the best in their specialized fields. They’re a who’s-who list you’ve probably never heard of, coming from the Research, Motorsports, and Production Development areas within GM. Each one of them can take immense pride in the fact they started the development of an incredible engine.

Koerner adds, “From the beginning, we had people from every corner of GM in heated debates over how to do this or that. A great example is the simple solution the team created to locate the machining equipment on the raw engine block castings. Instead of using external reference points, the machining equipment actually reaches up inside the block to locate the cylinder cores and center on them. This way, core shift and cylinder-wall thickness issues are practically eliminated in the machining of the engine block. It was a simple solution to a complex problem that solved multiple issues. The Gen III V-8 project is loaded with situations like this that came from the team.”

One of the key aspects of the Gen III V-8 is that the head bolts pull from the bottom of the engine block. By using extra long bolts that thread into blind tapped holes in the webs of the crank mains, the strength of the block is maximized, block weight minimized, bore distortion is minimized, and the block and bolt stretch can be used to create a consistent clamping load on major components.

Another Pushrod Engine?

During interviews, a few of the early Gen III V-8 team members commented that they thought they had done something wrong to end up working in the development of a new cam-in-block V-8. GM cylinder head engineer Ron Sperry summed it up, “Literally, on my previous assignment I was working with many of the greats in racing on a future racing cylinder head. My GM leadership called me up out of the blue to tell me to go to the Tech Center (GM’s North American technical development campus in Warren, Michigan) to figure out how to make more power with the LT1 production V-8 engine program. The LT4 top end was the result of that work but there didn’t seem to be much of a future with that architecture. I figured I’d done something wrong and my career was over. Seriously. At that time, all we were hearing was V-6 this and inline 4-cylinder that. As far as the rank and file engineers were concerned, GM wasn’t going to build another production V-8 — and it sure as hell wasn’t going to be a pushrod V-8 if they did!”

The Camaro and Firebird were powered by Gen III V-8s from 1998 until they were discontinued in the 2003 model year. These vehicles have plenty of performance components available for them and can be drastically improved with very little investment of time and money.

Well, Sperry soon found out GM was building a V-8, it would be pushrod design, and the Stephens/Koerner team was going to leverage as much knowledge and experience as they could to make this engine a winner — which was why Sperry and the rest of the team were there.

This tech tip is from the full book, HOW TO BUILD HIGH-PERFORMANCE CHEVY LS1/LS6 V-8S.

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Building an Engine From Scratch

When building anything from a clean sheet of paper, it is interesting to understand what happened first, then second, and so on. In the case of Gen III, it went like GM does almost all of their in-house development.

First, the Advanced Engineering side of GM Powertrain proposed an engine design of rough proportions. GM has an extensive skunkworks system throughout the company that constantly creates and/or seeks out, then integrates products, processes, services, etc. to generate proposals for GM leadership to determine how, when, or if this technology will end up on GM vehicles.

In the case of the Gen III V-8, Stephens made a verbal request for an initial design because he needed to show the leadership above him something in his initial pitch. Alan Hayman and his small team of engineers in Advance Design, Powertrain — which included Jim Mazzola and Tom Langdon — did this initial work.

Hayman said, “We had little time, and there wasn’t an official program underway when Stephens came and asked for an initial design. So, we looked around Advanced Engineering and saw a V-6 engine design we were working on for the V-6 Chief Engineer, Volker Harhaus, called the ‘Venture V-6.’ This engine was intended to replace the 4.3- liter V-6, which was similar to the Gen I/II V-8. We used many of the ideas proposed in the development of this new V-6 (which was never produced) to create the Gen III V-8 idea starter.

The intake manifold, what GM Powertrain calls the IAFM, for integrated air/fuel module, is extremely lightweight, but needed some help to keep the floor from resonating. Doug Duchardt, former head of GM Racing, did the engineering work to come up with the three stands needed to be cast in place inside the intake — you can see one of them in this cutaway — to dampen the resonance.

The oiling system, especially the stressed-member oil pan, was by far the most challenging aspect of getting the Gen III LS1 V-8 to work in the ’97 Corvette. This drawing from early 1992 shows the idea of putting the gerotor oil pump at the front of the engine and the location of the oil passages in the block. This is very close to how the Gen III oiling system works.

The oiling system for the Gen III V-8 pulls oil from the oil pan into the crank-driven gerotor pump at the front of the block. The oil is then sent down the main galley on the driver side to the oil filter, and then back up the back of the block to the main feed galley that runs through the lifter bodies. Oil reaches the top of the engine through the pushrods, just like the last 50 years worth of small blocks. Oil returns to the oil pan through a series of drain-back passages throughout the heads and block.

“The first design we proposed, on a project we called the Venture V-8 or VV-8 internally, was denoted as project 57B. There was actually a 57A, but the ‘B’ version had already been chosen over ‘A’, so the ‘B’ is what Stephens discussed with the leadership.

“The 57B design had the following:

The 57A design was similar to the ‘B’ design in all respects except it was penciled with 5 head bolts per cylinder — which is the design the Gen I/II small-block V-8s were built with. Much consideration and computer modeling was performed by a team run by Engineering’s Roy Midgely. Dan Hancock, the Director of Advanced Powertrain, at the time was behind the 4-bolts per cylinder 57B design. The design team evaluated this aspect from many angles and presented them to Stephens who eventually made the executive decision that the 4- bolts per cylinder design was the right choice for the engine.

The development of the front-drive was considered in every facet of the engine. This contributed to most of the accessories being nearly direct mounted and reduced the amount of noise the front-drive created. GM Powertrain’s Stan Turek headed up this component set. One of the neat features the team discovered was that by giving the A/C compressor its own belt, they could reduce the noise by a substantial 7 decibels.

The LS1 Beta engines showed that the engine would require some help to improve its bay-to-bay crankcase breathing. This was expected, but the “windows” that needed to be added were more substantial than expected. The early LS1s have a machined hole through all the main webs. Later, cast-in ports in the main webs (shown), introduced first on the LS6 and then on all Gen III engines, ensure there was sufficient area for the oil vapor to move around in the bottom of the engine at high RPM.

The ultra-thin, centrifugally cast, iron cylinder liners have serrated backsides (arrow) that lock them in place during the casting process. To achieve tight enough tolerances for this to work, GM Powertrain engineers created advanced semi-permanent casting-core technology. Standard core shift, which is the movement of the molds during the molten metal pouring, would have otherwise made this setup impossible.

Jim Mazzola, of GM Powertrain Advanced Engineering, remarked, “Looking back, those were pretty exciting times. From the initial design to the difficult refinement stages, we felt like we were building GM’s future. Our bread and butter. The entire team felt very strongly about raising the bar on pushrod engines. This feeling is unusual in the Advanced Engineering group as we work very much in the background of engine development, so it was very special.”

Making It Happen

The team was led on the ground by Gen III Base Engine Manager, John Juriga, who worked 19 years in the small-block V-8 program. Juriga adds, “I ran the Gen III V-8 program initially for Anil Kulkarni, and then Ed Koerner, in the creation of things like the block, heads, crank, rods — essentially everything short of the fuel system, catalytic converters, and electronic controls. We were told from the beginning by the GM leadership that the initial analysis of the research pointed to a pushrod engine, but there was a question as to power production. From the beginning, no one in the trenches on the team questioned whether power production would be an issue if we got the ports and valvetrain right.”

One of Chief Engineer Koerner’s hard and fast requests was for an in-line valvetrain. This meant there would be no side angularity in the pushrod or offset rockers to get the pushrods out of the way of the intake port. While offset valvetrain components are seen all the time on hot-rod engines, remember, GM needs to build engines that last over 100,000 miles with no problems.

The First Line — Injector Angle

So, the basic structure of the Gen III V-8 was suggested by Advanced Engineering, but the engine design process was just getting started towards a final design. Most importantly, the final creation of the most important component was yet to come — the cylinder head. The responsibility for this would fall on Ron Sperry. Ron’s brother, Ken Sperry, has been a leader in port airflow development at GM for decades and was brought in to lead the team creating the port and combustion chambers for brother Ron’s Gen III V8 head. Other airflow team members included Advanced Engineering’s Alan Hayman, valvetrain wizard Jim Hicks, and some computer-based engine analysis techs (the project started with Chuck McGuire and ended with Jerry Clark doing this).

The angle between the fuel injectors and valves was the first line locked in during the creation of the Gen III V-8. Since fuel-injector technology in 1991 wasn’t what it is today, the team started with the best injectors available and built the engine around them. This was done to maximize efficiency and power production while minimizing emissions.

Ken Sperry summed up this part of the project, “the members of the team had all worked together either on the Gen II V8 development or other projects, so there was immense knowledge and talent in each member and we respected each other. The team members were very comfortable speaking their minds— which can be good and bad. But that debate was usually towards making the product better, which I think is a major reason it is so good.”

One of those initial starting points was fuel injector placement. Koerner starts us on this point, “At the time, fuel injector technology wasn’t nearly what it is today. The choices were very narrow and the team knew getting this right would be critical to achieving the power, emissions, driveability, and other requirements set for this engine. Because of this, the fuel-injector location in relation to the valve angle placement was the first line set in the creation of the cylinder head and intake manifold.”

Ron Sperry’s take on this issue concurs, “The first step in building the top end of the Gen III V-8 was to locate the angle of the fuel injector to the valve angle. So the team focused on getting the fuel injector fuel cone (the spray) to hit the back of the intake valve on the far side of the valve. This did result in some airflow compromises, but nothing drastic. Later on, fuel-injector advancements allowed improvement in avoiding port wall wetting, which made the injector location less critical, so we’d do things a little differently now, but for that time, it was the best choice.”

The next step was to develop the intake and exhaust ports. Koerner had success with replicated ports in past applications and wanted them on the Gen III V-8. He also wanted the valvetrain to be in line, which was a constraint to port location. Add in the problem of the four head bolts getting in the way and it’s easy to see there was little room for the intake ports. Both Sperrys chuckle, “People wonder where the ‘cathedral’ intake port (tall and narrow) design came from. Hell, there wasn’t really any room between the head bolts and the in-line pushrods for a traditional port. We just kept squeezing the port narrower and taller until we got the flow ‘right’ — the cathedral port got us the port volume in the small space available to us. It was as simple as that.”

Regarding the efficiency of the intake port, Ken Sperry adds, “The intake port was so good, we actually had to slow the airspeed down. We found that an airspeed of more than 350 feet/second could easily be achieved, but this would not allow the air to ‘turn’ at the short side radius just before the valve seat—it would just skip past and all the air would go through the backside of the intake. This effectively reduced the swept area of the intake valve and hurt flow and power production.” So to correct this, “the short side radius and back of the bowl shape resulted from intense computer modeling and physical testing to get the air to turn, use all the valve to get the air in the combustion chamber and induce swirl without a lot of bandaids that ultimately cost you in total airflow.”

When they had the intake port roughly determined, the Sperry brothers’ team quickly came up with a very efficient exhaust port and went to work creating a port/combustion chamber combo that netted excellent flow characteristics. Their experience really shows here. Comments Ron, “High raw flow numbers are not worth a damn unless everything is working to maximize complete combustion. The desired result is to achieve a high yield combustion pressure pushing the piston down. This is what creates power and also results in excellent emissions numbers.

“We worked with what we call the Hurricane and Tornado-style combustion swirl effects when developing the port/chamber combo for the Gen III. The hurricane swirl has a wide diameter while the tornado has a very tight swirl. To put this in specific numbers, the hurricane swirl would result in 1 complete swirl per fuel injection cycle, while the tornado swirl would result in 1.2 or more swirls per fuel injection cycle. To give you an idea how valuable this is, we gained 8 hp by achieving 2 swirls per fuel application.”

The cooling system for the Gen III V-8 is different from previous small blocks in that the thermostat is on the inlet side of the engine. The coolant circulates through the engine and heater core until the engine is up to temperature — bringing the engine up to temp and providing heat to the interior in only a short amount of time. The steam vents in the top of the engine help to get the steam pockets out of the engine that cause localized hot spots that lead to detonation and pre-ignition.

As a note, Ron Sperry made a point to clarify that the Gen III V-8 engine is not considered a “fast-burn” engine. He explains, “The fast-burn intake port was designed before we had really powerful computer modeling of the intake flow. Before the Gen III head was created, we did most of our testing on physical models and the data seemed to show us that shooting the air/fuel mixture vertically into the combustion chamber with as much force as possible would net power. Luckily, we were able to use advanced computer modeling in the design of the Gen III head and saw that in actuality the gain was negated by the air/fuel charge actually pushing against the piston coming up in the bore—eating power! So while the fast-burn port/chamber design did produce a power gain, the Gen III V-8 port produces more power with the use of an improved ‘swirl’.”

Single-Cylinder Testing

The initial physical testing was done on a single-cylinder test engine, called a hydra engine, in the Advanced Engineering area of GM Powertrain. This engine is no more than a low-RPM test bed (they usually operate at less than 3,500 rpm) that can have different cranks, connecting rods, pistons, and cylinder heads easily installed. These test engines were widely used before today’s computer capability, and the Gen III V-8 early proto designs were run engine, but on the initial engines, the crankcase bay-to-bay breathing was not sufficient. At 1,200 rpm, having the on the hydra. These engines were used to evaluate coefficient of variation (COV), indicated mean effective pressure (IMEP), swirl, and other parameters. Using the hydra, Hayman, Jim Hicks, Rick Frank, and others worked with the Sperry’s to lock down the valve angle, coolant flow, valve cover rail location, and other aspects.

Dyno Development

As with any development project, there would be failures and with the Gen III V-8 development. While the engines showed impressive power output in the first dyno runs, certain deficiencies were discovered.

The Gen III V-8 deep skirt engine block design provides impressive rigidity and reduces the noise coming from the two front cylinders rising while the two rears were falling forced oil into the front cover. To fix this, the area under the intake was opened up to allow bay-to-bay breathing capability and small ‘scoop’ ports were cast into the block on the side of the main caps (an idea patented by Advanced Engineering’s Jim Mazzola and Terry Black). This eliminated the initial idea of putting the alternator and starter in the area between the intake and lifter bay.

The factory powdered-metal main bearing caps are held in the block with six fasteners for maximum strength and rigidity. The deep skirt design hinders crankcase bay-to-bay breathing, so the main caps do not extend all the way to the side wall of the block below the bolt bosses, which leaves room for the main webs to have windows that improve airflow. The deep-skirt block design has impressive strength and rigidity, which is important for the aluminum-block versions of the Gen III. This design aspect produces an unusually strong iron block that is capable of much more power than the production engine makes. All the main caps are held in place with four vertical 10-mm-diameter bolts and two 8-mm-diameter bolts.

Later on in the development, it was discovered that at high RPM, the pistons moving up and down in the bores pushed oil vapor and air in all the wrong places in the crankcase. The deep skirt and main caps were sealing off each pair of cylinders, limiting where this pressurized oil vapor could go. On at least one of the prototype engines, the subsequent buildup of pressure blew the rear section of the block off. The short-term solution to this issue was to machine holes through all the main cap webs and the long-term solution was cast-in bay-to-bay breathing “windows” in the webs. Additional windows were developed for the LS6 high-RPM, high-horsepower engine package.

Also, from the beginning, the Gen III V-8 was designed to produce overall net power. This meant common parasitic power losses, like friction and pumping losses, were to be minimized from the beginning. One interesting byproduct of the lowered power losses was poor idle quality. It was discovered idle quality is usually improved by some frictional losses. On Gen III, with its roller lifters, roller rockers, and low tension piston rings, the only friction at idle is really the piston moving up and down in the bore and the rocker arms wiping across the valvestem. To improve idle quality, the development engineers “built-in” a load on the engine when needed.

In the Vehicle

One of the more interesting challenges involved the oil pan and oiling system. Since the LS1 sits very low in the Corvette, the oil pan is extremely shallow. Hayman details the scene, “The deep skirted engine block is a winner with regard to strength, rigidity, and NVH, but combine that with a shallow pan and it becomes difficult to get the oil away from the crank and out of the bottom of the engine. The tight confines of the engine block walls increase the chances of the crank “roping” a lot of oil on it, which results in a parasitic loss of power. Also, the spinning crank whips the oil all over the engine instead of leaving it in the oil pan. To visualize this, imagine pouring oil on a fan pointed upwards. Obviously, the oil would end up everywhere except on the fan.”

The ignition system is another one of those component sets that looks deceivingly simple. The four coil near-plug setups on each valve cover are wired to the powertrain control module and fire based on readings from the crank and cam sensors.

This problem really showed itself in the early validation testing stage of continuous high lateral loading. Some of the early LS1 test engines would struggle to get constant oil flow, so there were many, many tuning changes made to the design of the oil pan to minimize this issue. A special team consisting of Brian Green, Tommy Morrison, Nick Cole, George Fultz, Dave Klaasen, Tom Bierbauer, Jim Minneker, and others thrashed long and hard to get this issue under control. Fultz would eventually help GM design a special dyno cell to duplicate the many challenging scenarios the LS1 engine team encountered in vehicles. This will allow the testing of future engines to occur much earlier in the development process than it did in the Gen III V-8 development.

The Vortec V-8 engines in all GM full-size trucks and SUVs have identical architecture to the engines in the Corvette, Camaro, and Firebird. The GM Vortec engines have different displacements, cast-iron blocks, some wider sealing surfaces, and a different intake than the LS1 and LS6, but the same performance parts will easily bolt on and make power.

Passing the Torch

In late 1997, with the LS1 launch successful, Koerner was given a new leadership position inside GM Truck. Sam Winegarden, a GM leadership veteran of the 3800 V-6 and Northstar V-8 engine programs, was given the Chief Engineer job for the Gen III V-8. “From the beginning, I knew this program was big. It was obvious this team was working on an American icon, and they held the job in that context,” said Winegarden.

From the beginning, Winegarden had some big projects to launch and run smoothly in the spotlight. Some of them would include leading the Gen III V-8 team through the truck engine launch, the introduction of the LS6 385- and 405- hp engines, and the LQ9 345-hp Escalade truck engine. The truck engine requirements took the daily production from approximately 2,000 engines per day to over 8,000 engines per day. Winegarden commented, “I’m very proud of how the engineering and manufacturing team handled that. The Romulus, Michigan, engine assembly plant broke the existing Powertrain record for ‘launch speed acceleration’ — a measure of the production facility going from startup to maximum production levels. Then, six months later, the St. Catherines, Ontario, Canada, engine assembly plant took some of the lessons learned from the Romulus launch and beat the Romulus record in the same category. Now, both plants are usually number 1 or number 2 in the Harbour Report on plant efficiency and both are beating the competition in Quality ratings of problems per hundred, or pph.”

Considering the complexity of building engines in a large-scale manufacturing facility, these achievements are incredible.

The LS6 Story

Winegarden likes the LS6 story because he believes it really showcased the ability of the Gen III V-8 team to raise the bar. “Dave Hill, the ’Vette Chief, success,” said Winegarden. This would obviously be a huge understatement.

The 405-hp LS6 Z06 Corvette engine is really only the beginning of the potential the Gen III V-8 architecture has shown with its “simple pushrod design.” Considering that this engine exceeded all expectations at its introduction, has a design that honors the legacy of the small-block Chevy engine, and will be the engine design hot-rodders talk about for years to come, it’s a great win for the GM Powertrain engineering team.

To think the LS6 came from the trenches of the GM organization leads one to wonder what other cool, amazing power parts lurk down there!

The LQ9

Winegarden continued, “Once the LS6 program was up and running, various members of the V-8 team started to look around at other possibilities. Tim Cyrus was the Assistant Chief Engineer for the truck engines, and when he saw the LS6 castings, he started pushing for a 6.0-liter performance package. A few of his dyno team members and he did the work to create a head, and Cadillac decided to use it to further distinguish their Escalade in the full-size SUV portfolio.

“The LQ4/LQ9 aluminum head ended up having LS6 ports but slightly larger combustion chambers (72 cc vs. the LS6 64 cc) to accommodate the desired compression ratio of the 6.0- liter engines. It was neat because without a lot of work, we had the 345 hp and 380 ft-lb of torque LQ9 engine that the Cadillac folks were thrilled with.”

Written by Will Handzel and Posted with Permission of CarTechBooks

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