As the Head Calibrator at Gwatney Performance Innovation, Ryan Stevens eats, sleeps, and dreams about performance. So when it came to his own performance machine, he had a couple of requirements in mind that were non-negotiable.
“The whole idea was to build an 8000-plus rpm monster that was naturally aspirated, and to make 750-plus flywheel horsepower with less than 400 cubic inches,” he explains.
And that’s where the big challenge came into the picture. The idea of making that much horsepower and RPM meant that parts selection was incredibly critical — one wrong choice and the whole project could come to a screeching halt short of its goals.
The engine, built in-house at Gwatney Performance Innovation, relies on an aluminum 9.240-inch-deck LS3 block and a mix-and-match assortment of OE LS engine parts. The stock L99 forged-steel crankshaft with 3.622-inches of stroke was combined with a set of OE Pankl-manufactured titanium LS7 connecting rods that measure 6.067-inches long. Final displacement checks in at 377.91 cubic inches.
The rotating motion is turned into horsepower with the help of a set of hard-anodized Diamond Racing forged 2618-alloy aluminum pistons; with the 13cc dome on top, they help to pump the compression ratio to 13.41:1 and make the big power.
An engine’s induction system is the be-all end-all of its performance capability, especially in the case of a naturally-aspirated engine such as this one. If the engine lacks the ability to breathe, its ability to make power will be severely compromised. That pushed Stevens to check in with Chris Frank of Frankenstein Racing Heads to set up the 821 casting LS3 aluminum heads into the FRH CNC machine to tune them up and provide the required airflow for the high-compression mill.
A low-lash solid roller from Cam Motion was selected to actuate the valves. The camshaft checks in .782-inch lift on the intake side and “in the 250s for duration”, along with .765-inch exhaust lift and duration figures “in the 260s,” Stevens says.
Lobe Separation Angle of 110 degrees is used for this particular camshaft. The relatively wide LSA combined with the steep duration figures plant this camshaft squarely in the high-RPM performer category.
“I may put a tad smaller cam in to bring the peak down a little and make it a little stouter under the curve,” he explains.
More LS parts-bin pieces were used in the form of the titanium LS9 intake valves, which measure a whopping 2.165-inches in diameter. Exhaust valves are from Manley and measure 1.59-inch. The head gaskets are GM OE LS9 multi-layer steel items.
The intake manifold is one of Edelbrock‘s Super Victor LS3 carburetor-style intakes, and that’s part of what caused this unique project to catch our eye. Exhaust is handled by a set of 304 stainless steel 1 7/8-inch long tube headers that feature 3.5-inch merge collectors and merge spike to maximize the exiting airflow.
“I wanted the best breathing combo, yet since I still run the 6-speed automatic transmission, I have to utilize factory control modules,” Stevens says.
And that’s where his tuning expertise enters the picture. On top of the Edelbrock intake manifold sits a 4500-flange Accufab throttle body that’s driven by a factory-style drive-by-wire setup using a custom bracket and linkage. Stevens procured and developed a servo system to run the drive-by-wire throttle body management.
The engine is controlled with a stock E38 engine control management system; a T43 transmission controller is also onboard, and Stevens tunes the whole works with HPTuners and EFILive. 850cc LS3-style fuel injectors are used along with stock LS3 coils and MSD ignition wires to keep the spark lit. Fuel is supplied through a ZL1 pump assembly and control module, along with a voltage booster to ensure there’s enough juice to the pump.
“Tuning has been a nightmare, but I’ve pretty well gotten it dialed in,” Stevens says. “From trouble with reduced power engine faults to the throttle area scaling, it took a lot of time to get it close. I have approximately 50 hours in the design and testing of the throttle body system.”
When one sets out a solid goal for performance, then attacks that goal with a well-thought-out plan, the goal is often achieved.
“I’m in the tuning process now on the chassis dyno. With a locked converter I’m in the 640-plus rear-wheel-horsepower range at 7,800 rpm,” he says.
Whatever he does next, one thing is for sure — this is one stout LS3. And the thought process and innovation behind the project exposes his skills behind the laptop and in front of the parts selection process.