Holley Stealth Ram EFI Kit - Grand Slam Stealth RamPosted in How To: Engine on March 1, 2008
Electronic Fuel Injection (EFI) has clearly come out as the fuel-delivery system of choice in every type of motorsport. The advantages are clear, and it's no secret that you'll feel better throttle response driveability, and you'll likely see an increase in fuel economy and engine power. Our editor, Rick Pw, pointed out that, in a perfect world, an EFI kit should make no more power or improve fuel economy over a carbureted system. But the chances of finding a carb that is perfectly tuned for the absolute best mix of fuel economy and power are slim. And if you factor in elevation and climate changes during driving, it is nearly impossible for a carb to keep up with a wideband EFI system. The control module of the EFI takes multiple parameters into account and makes adjustments based on data delivery from the O2 sensors, MAP sensors, intake air temperature sensors, and coolant sensors.
There are two main types of EFI systems: throttle-body injection (TBI) and multipoint fuel injection (MPI). TBI fuel-injection retrofits are nice because they're easy, they're cheap, and they require minimum modifications as a TBI system bolts to the existing manifold. If you're looking for a kit with better throttle response, you'll need to step up to an MPI kit, complete with a replacement manifold and a fuel injector for each cylinder. The cream of the MPI crop is tuned port injection (TPI) kits, and this Holley Commander 950 Stealth Ram MPI system that can supply a small-block Chevy engine enough fuel for 300-670 hp. We teamed up with DC Performance in Los Angeles, to install and tune Holley's Stealth Ram kit on a bone-stock '75 Chevy 350 engine. Unless you are very experienced with tuning EFI systems, we suggest letting professionals like the guys at DC to do your engine tuning for you. The installation of the kit itself can be done at your house if you have enough time, but the tuning is best left to the pros. The Stealth Ram kit is also not 50-state legal, so you'll have to have a '75-or-earlier vehicle to use it in California.
DC Performance highly recommends checking out the engine before putting on an expensive system like this. It's always exciting to see an untouched (since 1975 when it was built) engine get ripped into. Before this, the biggest mod it'd seen was the Thorley headers on the sides of the block. That being said, it was ugly under the hood. The red and blue lines running over the manifold are discharging the air-conditioning system. Since the line from the A/C compressor to the condenser had to be removed to get the Stealth Ram's plenum on, we had no choice. We'll have to pick up a custom A/C line to run it past our new Stealth Ram system.
The throttle response was improved, as were the driveability and fuel economy. But did we make more power? DC Performance tuned the engine prior to the teardown so it would be running as well as it could with the carburetor on it. Once they were done, they pulled off initial dyno numbers and proceeded to remove the top end of our stock 350. When the kit was finished, DC Performance strapped our test truck back on the dyno for its final numbers.
Peak Horsepower - 147.50 hp
Peak Torque - 216.50 lb-ft
Peak Horsepower - 154.90 hp
Peak Torque - 221.47 lb-ft