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Mark Stielow installs the supercharged LS9 into his newest Camaro project.
Addressing all the details is paying off for Mark Stielow as the supercharged 7.0-liter LS9-based engine for his new ’69 Camaro “Hellfire” project boasts 957 horsepower, a jump of 80 horsepower over a similar LS9 built for his well-known “Mayhem” ’67 Camaro two years ago.
“It was all the little stuff together that added up,” says Stielow, who will debut the car at this year’s SEMA Show.
Some of the noticeable differences are a fully blueprinted Eaton supercharger, redesigned air inlet, more aggressive overdrive pulley and a camshaft with unique profiling.
The 427ci LS9-based V8 pulled 957 horsepower on the Lingenfelter/Thompson dyno with peak torque of 970 lb-ft.
“Going from 13 pounds of boost in the Mayhem engine to 15 pounds allowed us to get up to 957,” says Stielow, noting peak torque was 970 lb-ft at 3,700 rpm.
The engine was built at Lingenfelter/Thompson Automotive Racing Engines in Wixom, Michigan. Brian Thompson prepped the LS7 block by adding ARP hardware and adapting piston-cooling jets to the main oil galleys.
Close to the limit
“We’re right at the structural integrity of the LS7 with this much power. One of the big durability problems is that you can’t use the production LS9 squirters in the LS7 block because of the longer stroke we’re using,” Stielow tells EngineLabs. “Putting the jets in the main web really keeps the durability.”
The 4-inch-stroke crankshaft is from Callies, and it supports Oliver connecting rods and Diamond pistons. Compression ratio is 9.0:1. Stielow retained the factory dry-sump oiling system but upgraded to a larger 12-quart Peterson tank. He also focused considerable attention on getting that oil cooled after it’s scavenged from the pan.
The foundation is a LS7 block fitted with Callies crank, Oliver rods, Diamond pistons and ARP hardware. Note the piston cooling jets tapped directly into the main oil galley.
“With Mayhem, I went from 180 degrees oil temperature to over 300 in just three laps, and I had a big oil cooler in that car,” says Stielow. “I worked with C&R Racing to spec out a NASCAR-sized cooler. We can now make that power over a longer period of time with more attention to the sub systems that keep the engine happy.”
CNC-ported LS9 heads top the short-block.
The cylinder heads are CNC-ported LS9 models that flow “a little more what a LS7 will.” Working with fellow GM engineer Dave Mikels by running computer simulations, a custom camshaft was developed with unique overlap and lobe profile. The rest of the valvetrain includes stock LS9 rockers with new trunions, stock lifters, Del West titanium intake valves, Inconel exhaust valves and Lingenelter titanium retainers.
The Eaton R2300 supercharger was carefully blueprinted at the factory, then fitted with a custom blower inlet snout. With the help of a Lingenfelter pulley, the supercharger is driven at a 3.20:1 ratio.
Letting in the air
“On the LS9 or any other blower motor, the inlet restriction is really important,” says Stielow, adding that he designed an induction tube that sports a 4-to-4.5-to-5-inch expansion and flare. “The induction tube is an integral part of the equation getting air into the blower. K&N supplied filter elements large enough for the tube. Brian Thompson also spent a lot of time redesigning the blower inlet to get the best airflow possible into the blower inlet. The stock 90mm throttle body was retained to keep good drivablility. There are larger ones on the market but in our experience most have drivablity issues.”
Stielow focused considerable attention on the air inlet and cooling systems.
To obtain correct inputs for the E65 ECU, Stielow sourced a diesel part number for the MAF sensor to fit in the 5-inch portion of the induction tube. Rounding out the top end of the motor are larger injectors and stock LS9 ignition.
The engine as it sits in the Camaro.
In addition to a stronger engine, Hellfire will be much lighter than the previous Mayhem car — which won the 2012 Optima Batteries Ultimate Street Car Invitational.
“Mayhem was really fast and it was easy to take weight out of the back of the car,” says Stielow. “For this car I wanted less weight over the front axle, so the entire front clip is carbon fiber. That took 120 pounds off the nose. This car should come in around 51 percent front weight where my last car was 53.”
Wiring and interior finishing are left on the car, and it’s scheduled for initial track testing in mid-October before heading to SEMA.
Artist’s rendering of the ‘Hellfire’ Camaro.
