Video: This High HP LS3 Uses Custom 4bbl Drive By Wire EFI

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 GM parts bin and a well-thought-out plan are the keys to this unique, well-built LS3.

The GM parts bin and a well-thought-out plan are the keys to this unique, well-built LS3.

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.

Stevens ported the Edelbrock LS3 intake manifold in-house at Gwatney Performance Innovations to match up with the FRH CNC-ported cylinder heads.

Stevens ported the Edelbrock LS3 intake manifold in-house at Gwatney Performance Innovation to match up with the FRH CNC-ported cylinder heads.

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.

(Left) Titanium connecting rods from an LS7 engine were used for their strength-to-weight ratio. Diamond pistons are affixed to the pin end with a set of Trend Performance DLC-coated pins. (Left Middle) 821 cylinder head castings have been tuned up by Chris Frank at Frankenstein Racing Heads. (Right Middle) Titanium LS9 intake valves and Manley stainless-steel exhaust valves are on board. Weight reduction in the valvetrain area is critical for this build. (Right) T&D rocker arms are employed atop the valves.

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.

The Cam Motion bumpstick.

The Cam Motion bumpstick.

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.

Custom, custom, custom--but Stevens achieved his end goal of building big power from a unique combination. He estimates over 50 hours were spent just getting the throttle body servo design and tuning lined out.

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.”

(Left) There's just a tiny dome on the pistons. (Middle) The use of the parts-bin pieces -- like the LS3 block, head castings, crankshaft, and connecting rods -- where it made sense, helped to keep costs in the 'sort-of-manageable' range for the build. (Right) Hard anodizing on the Diamond pistons helps in high cylinder pressure, high temperature applications. Could there be nitrous in the future for this bullet?

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.

About the author

Jason Reiss

Jason draws on over 15 years of experience in the automotive publishing industry, and collaborates with many of the industry's movers and shakers to create compelling technical articles and high-quality race coverage.
Read My Articles

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