Building an engine capable of supporting big-time power under the thermal load of supercharging is a tall order. Doing so on a car that will see the road daily only raises the stakes. Taking into consideration that the customer is Hank Manley, the founder of Manley Performance, pushes the pressure of perfection over the top. Mostly retired these days, Hank decided that he wanted to have an engine built for his daily-driver Corvette and turned to the Manley catalog to fulfill his desires.
“This is the only car I own,” Manley says. “I live in Florida, and I spend the summer in Colorado, and I drive the car every day. I had some slight trepidation about having this much power on the street, that it would just be annoying and obnoxious, and it’s not. It’s pretty darn docile on the road and makes 700-plus at the wheels on a chassis dyno.”
Manley says that the engine has been installed in the car for a about a year and a half, with approximately 20,000 miles on it since then, and there hasn’t been a single issue.
“It’s a stupid amount of horsepower, but I love it. It smokes the tires in first gear, or from a 35 mph roll, but I’ve never tried to break them loose from highway speed,” Manley laughs.
The company, celebrating 50 years in business in 2016, is proud to celebrate its longevity, as the average life of a business in the United States is around five-and-a-half years. This package was created to showcase its abilities and knowledge supporting the automotive aftermarket over the last half-century.
“We developed these iconic engine packages; I wanted a 427 in this car, and it came from the factory with a 376 cubic-inch engine. The goal was to showcase the products we offer and this project does exactly that,” says Manley.
Let’s take a look at the components that were used in the build, why they were chosen, and how everything came together to create a rock-solid platform that’s reliable, relatively well-behaved, and most of all, fun to drive.
Internal Component Selection
One interesting point to consider with this engine build is that Manley fully expects this engine to have OE-type durability; that is, to run thousands and thousands of miles with proper maintenance, and with nary a hiccup when the loud pedal is pressed.
From the factory, the ZR1 is motivated by Chevrolet’s supercharged LS9 376 cubic-inch engine, which is based on the LS3’s engine block. Factory dimensions check in at 4.060-inch bore with 3.62-inch stroke; the compression ratio set at 9.1:1 with the Eaton supercharger on top. Factory-rated performance tops out with 638 horsepower at 6,500 rpm and 604 lb./ft. of torque at 3,800 rpm, owing to the 2.3-liter TVS supercharger’s “instant-on” nature.
With the stated performance objectives in mind of low maintenance and improved performance, Manley turned to his company’s catalog for a complete LS rotating assembly, and put longtime employee Tom Razzano in charge of detailing the specific parts and pieces used for the build.
“I went to Scoggin-Dickey for a an LS9 block and cylinder heads, the appropriate engine covers, and oil pan, so that we could take the old engine out of the car in one piece and install the new one,” says Razzano. “Since the only part we were going to re-use was the supercharger, we shipped the rest to Total Engine Concepts (TEC) in Riviera Beach, Florida. TEC’s owner, Mike Kovacs, was selected to do the machine work and assemble the engine.”
Transferring the power for this beast is one of Manley’s 4.100-inch stroke 4340 forged-steel crankshafts (PN 190158, available at Jegs), that uses LS 2.559-inch main journals, 2.100-inch rod journals, and has a 1755-gram bobweight. It also uses the 58-tooth reluctor wheel and clocks in between 50-52 pounds after final machining. The counterweights are fully profiled, while the rod journals have been lightened for weight reduction. The non-twist forging has been heat-treated, stress-relieved, shot-peened, and magnafluxed.
Manley’s forged 4340 Pro Series I-beam connecting rods (PN 14559-8) are in place, which feature a heavy beam for forced induction use. The 6.125-inch connecting rods are forged from aircraft-quality vacuum degassed material and use ARP 7/16-inch ARP2000 capscrews, and are also shot-peened and magnafluxed after machining.
The last piece of the rotating assembly, an octet of Manley’s LS pistons (PN 596065C-8) designed for the engine, use a -20cc dish and 1.065-inch compression height. The pistons use a low-drag 1.5 mm/1.5 mm/3.0 mm ring pack, and the top ring is .250-inch down from the piston top to reduce the chances of overheating the ring face in boosted applications. They’re built from 2618 alloy and use a .030-inch offset pin location to aid in reducing startup noise, which mimics the factory design. A set of premium chromoly .927-inch pins are included with the kit.
It’s a stupid amount of horsepower, but I love it. – Hank Manley, Manley Performance
“We built it like it’s going to be a race engine. Checking clearances and adjusting for them with the bearing dimensions, honing the cylinders with a torque plate to get the correct piston-to-wall measurements, and setting the ring gaps where we wanted them,” says Kovacs.
As the basic package was not out of the ordinary for thousands of LS enthusiasts across the land, the decision was made to skip the engine dyno and go right to the step of installing the engine in the car.
“For us, this engine was really race engine-building 101. We were fortunate to learn a lot about the LS engines in the very beginning and we’ve kept that education going ever since. For simplicity’s sake, we shipped the engine to Howard at Redline Motorsports, where he installed it and broke it in on the chassis dyno,” says Kovacs.
Although the factory LS9 castings were used in this build, they were opened up in order to improve performance at all RPM levels. With all of the industry connections available to the Manley team, there was only one direction Razzano felt was appropriate for a build for the boss’s car.
Advanced Induction, in Concord, North Carolina, was chosen to perform the work, where proprietor Phil Odom put them under the knife. Odom CNC-ported the heads, then installed a complete set of valves, titanium retainers, valve locks, and spring package from Manley.
One topic that’s been resonating in conversation with induction specialists lately is the concept of not using flow numbers as the be-all, end-all of cylinder head development — the wrong way to go about it, according to Odom.
“Flow numbers in and of themselves aren’t something I am terribly concerned with. For any given application I prefer to calculate what port characteristics that I would ideally like to have, and then execute that as closely to the theoretical ideal as is possible, working around the inherent limitations of a given casting. There are certainly some considerations insofar as mass flow, overlap flow, and discharge coefficient goes. However, in my experience the steady state flow test results do not consistently or directly correlate with actual performance potential,” Odom says.
“I certainly do use the flow bench, but much of that is measuring air speed, examining how the port works, and examining what a given valve job/valve prep do insofar as overlap flow and reverse flow are concerned. Assuming a competitive design, the greatest effect on the customer’s success and longer-term happiness is the quality and consistency of machine work. Almost anyone can produce one single port that puts up high indicated flow numbers, but that is of little consequence to the end user.”
Custom CrN-coated titanium intake valves are used, with Inconel on the exhaust side to help handle the extra heat.
Manley’s NexTek dual springs (PN 221436-16) are designed for high-performance hydraulic roller camshafts controlling valve motion. NexTek springs are manufactured from high tensile chrome silicon steel that’s undergone a multi-step heat-treat process to improve fatigue life and minimize load loss over time. Manley’s heat-treated titanium 7-degree locks (PN 23617-16) offer maximum strength in a lightweight package. Manley’s LS 3-bolt timing set (PN 73236) with Torrington bearing and 9-way crankshaft sprocket also is used.
“With any street build durability is ultimately the most important concern. With power-adder applications that generally implies dealing with higher pressures, possibly some detonation on pump fuel builds, and the higher temperatures associated with that. This particular build saw the OE valves replaced with Manley’s excellent Inconel exhaust valves and titanium intake valves. Beyond that, it is common to slightly adjust seat angle widths, guide material, and guide to valve clearance to accommodate the additional heat imparted into the valvetrain and head,” says Odom.
After the cylinder heads were ported and assembled, they were shipped off to TEC for final installation.
Installation And Tuning
Camshaft and Drivability Concerns
Designing the camshaft to work properly in this application comes naturally to Tanner. As he spends the vast majority of his time calibrating different combinations on the chassis dynamometer, he’s seen what works not only in terms of absolute power production, but also in terms of usable power on the street — the butt-o-meter.
“Overlap is always the linchpin in any build. We use overlap in a naturally-aspirated build since the engine needs to take a big gulp of air – we need to take advantage of the atmosphere. The camshaft in this blown engine was not cut on a tight lobe separation angle – on a 120 LSA – close to the factory ZR1 camshaft. The intake and exhaust duration has been opened up to take advantage of the extra stroke. Valve lift was also increased, but not to where we’d see long-term valvetrain problems,” explains Tanner.
Tanner mentions that his familiarity with the engine’s performance is not only on the dyno, but sitting at a red light, pulling away in traffic, and in daily use affects his decisions in terms of selecting camshaft specifications.
“The build was cooperative between all of us,” says Tanner. “One of the keys here is that we picked the camshaft. We have a lot of street experience, and most importantly a street car needs to live and have good drivability and mannerisms.”
The camshaft was one of his creations, which allowed the new engine to take advantage of the extra crankshaft stroke and cylinder head breathing capabilities. This decision was left up to Tanner, as he was also responsible for engine calibration (see sidebar) and has developed a feel for how different engines and different camshaft profiles perform not only on the chassis dyno, but more importantly, in regular street use similar to what Manley puts this engine though on a daily basis.
“The car has presence, but we didn’t over-cam it because we had displacement, and we had the supercharger – there was no need to get greedy. The car makes a tremendous amount of torque, which is what a guy wants on the street,” Tanner explains.
“I could have made 20 more horsepower with a bigger camshaft, but that would have given up what Hank wanted out of this car – a no-BS, punchy-sounding, fast vehicle that doesn’t give him any drama.”
The engine calibration was solely Tanner’s domain. With a goal of complete streetability in mind, he tuned up the PCM to make monster torque down low while retaining the high-RPM power the new induction package permitted. The usable RPM range from the Roots-type blower has given Hank Manley the power he wanted from stoplight to stoplight, and as the hammer stays down.
“The car’s been all over the country, and hasn’t skipped a beat,” says Tanner.
Upper and lower supercharger drive pulleys were changed to pump up the engine while retaining its 93 octane limitations. A ZR1 typically runs around 9 psi of boost pressure, but with the upgraded internals, better-breathing cylinder heads, and improved camshaft, Tanner spec’d the combination to run approximately 15 psi in its current configuration. The TVS2300 supercharger is efficient past this range, according to Tanner.
“It all comes down to the camshaft. As good as the calibrator might be, we can’t fix pumping losses. If the camshaft isn’t right, I can’t fix that with the computer,” he says.
As shown in the dyno graph below, the car — with a non-aggressive calibration loaded into the PCM — turned the dyno roller to 712.6 hp and 725.0 lb./ft. of torque on the Redline dynamometer.
There are countless stories to be found all over the internet about “daily-driven” vehicles making huge-horsepower claims, but there is very little corroboration of the daily driver aspect. Hank Manley is not a boastful man; during the interview process for this article, he was clear in his discussion about the fact that this ZR1 truly is his only vehicle.
“There were three goals for the creation of this engine package for Hank’s car. It had to have neck-snapping torque, be super-fun to drive, and it better not break,” says Razzano. “This car has met all three goals with plenty of room to spare.”