Nearly a decade ago, Holley released a tunnel ram-style intake manifold that seemingly fit dozens of EFI and carbureted applications. From high-winding naturally aspirated monsters to mild-bolt-on junkyard builds to big-power turbocharged, heads-up cars, the Holley Hi-Ram is a seemingly a do-it-all intake manifold.
The manifold’s versatility comes from having different lids for a variety of applications. Holley and several other aftermarket manufacturers offer an extensive variety of intake styles, some even include an integrated air-to-water intercooler option for the boosted crowd. The Holley Hi-Ram, though, had one flaw—it was only designed for LS-based engines. Tens of thousands of LS-style Hi-Ram intakes later and Holley expanded the line-up to finally include the small-block Ford platform.
First to hit the market was the 9.5-inch Windsor Hi-Ram, and last year, the 8.2-deck version joined its big brother. Since then, the Ford market hasn’t stopped celebrating its release. For years, the Ford fans at FSC have lusted after the LS version, so it is no surprise that we snatched up one of the first 8.2-deck versions and put it to the test. We turned to Dez Racing, home of multiple NMRA championships, to do the dirty work and conduct the test on its in-house Dynojet chassis dyno.
Since boost is a part of so many lives, we felt a supercharged combination would be the best to showcase the Hi-Ram’s capabilities. Mike Dezotell of Dez Racing suggested a 1992 Mustang LX that belongs to the shop’s longtime customer Scott Charron. His sporty, 347ci powerplant is based on a Boss 302 engine block with a Callies crankshaft, Callies connecting rods, and CP piston package for a rotating assembly. The compression ratio is a rather mild 8.5:1, mostly because the car sees plenty of street action.
Dez Racing took a page out of its record-setting Renegade experience and selected a set of Edelbrock Victor Jr. cylinder heads that received a CNC port job to help increase airflow. The camshaft is a solid-roller unit, once again resorting to the shop’s racing experience to determine the proper specs, and they were tight-lipped on letting out the numbers.
The engine saw 29 psi of boost in the baseline test thanks to a ProCharger F-1A-94 supercharger and belt slippage was nonexistent as the setup employs a cog-drive pulley system. A massive, front-mount Chiseled Performance custom air-to-air intercooler keeps the air temps under control. The engine sucks down VP Racing Fuels C16, while Dez Racing installed a Holley EFI HP engine management system to replace the factory-supplied A9L ECU.
The baseline intake manifold consisted of a Holley SysteMAX lower manifold, a Cartech box upper intake, and a Holley 80mm throttle body. Utilizing that setup, Charron’s beloved street car cranked out a respectable 918 rear-wheel horsepower, a number that Dezotell felt confident could produce 8-second runs once the local drag strip opened up from its winter slumber.
For the test, we ordered the EFI version of the Holley Hi-Ram that comes complete with bullet fuel rails. After looking at a few lid styles, we settled on the cast aluminum lid with a side-entry. Holley engineers specifically designed its profile for use in Fox-Body Mustangs with low-rise cowl-induction hoods, such as a Cervini hood with a 2.5-inch rise, and it accepts up to a 95mm Ford-style throttle body. For the sake of consistency we retained the Holley 80mm throttle body used for baseline testing rather than adding a 90mm throttle body that Dezotell recommended.
The intake manifold fell right onto the engine, but Dez Racing’s Brian Machie did have to tap a new hole for an additional vacuum line for the LS-style MAP sensor. Another modification was a slight adjustment to the supercharger piping to accommodate the new angle of the throttle body. It just happens that Charron is quite handy with a welder and built his own blower piping, so he was able to make the necessary changes without much drama. Outside of those modifications, the installation was straightforward and could be tackled with basic tools.
Following a fairly straightforward testing regimen, we made the baseline pull, kept the vehicle strapped to the chassis dyno, and swapped on the new intake. As mentioned earlier, we retained the same 80mm throttle body to keep the testing a true A-B comparison. With the fuel curve untouched, Dezotell left the Holley EFI in Open Loop mode so the ECU added more fuel based on the oxygen-sensor readings. Dezotell also kept the timing set at 24 degrees for both dyno tests.
The Holley Hi-Ram intake manifold produced a better peak power rating of 946 rwhp, gaining 27 rear-wheel horsepower at the peak, but the real eye-opening numbers are in the midrange. At one point, the Hi-Ram bettered the old box intake setup by a whopping 62 rear-wheel horsepower!
The final boost numbers showed it lost 1.9 psi at peak, dropping from 29 psi to 27.1 psi. Boost is just a measurement of back pressure in the intake tract, and the drop in peak boost pressure simply means that the Holley Hi-Ram is less restrictive than the baseline combination. The supercharger pulleys also remained untouched, which is the true way to compare parts since that is a fixed airflow amount regardless of the boost reading.
Dezotell went on record with some notes about the test. The first was the Hi-Ram replaced a popular upper/lower manifold setup, but the gains might be different for other applications. He also felt that the intake was performing better than the rather impressive numbers revealed on the chassis dyno, as the fuel consumption increased dramatically on the dyno pulls. The extra fuel consumption indicates a significant gain in power, and in his opinion, that showed the engine could have been “driving” through the converter on the chassis dyno with the extra power. The looser converter would have an adverse effect on the output. He said the torque converter would be just fine on the drag strip because it would be loaded differently. Based on extensive dyno testing with this particular dyno for nearly 20 years, Dezotell was confident the car was capable of running sub-8.5-second elapsed times with the new output.
Form follows function as the Holley EFI Hi-Ram is now helping small-block Fords continue their greatness on the street and strip.