Battering Ram—Testing the Holley Hi-Ram on a supercharged small-block Ford engine

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.

Once the darling of just the LS world, the Holley Hi-Ram is now available for a wider range of applications. Holley got more aggressive in the Ford market and the 9.5-inch Windsor and 8.2-inch Hi-Ram intakes are proof. We opted for the side-entry lid, which helped retain our test car’s current supercharger piping package.


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.

Here is the 347 cubic-inch engine with the Holley Hi-Ram intake installed and the side-entry cleared his Boss cowl-induction hood without any issues. The Ford Performance Boss block is filled with a Callies crank and rods, which are mated to CP forged pistons. The top-end consists of a Dez Racing custom solid roller camshaft and Edelbrock Victor Jr. CNC-ported cylinder heads. The car sees plenty of street action and will soon be unleashing mid-8 second runs with ease.

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 final results show a peak gain of 27-rear-wheel-horsepower gain and the midrange saw as much as a 62-horsepower increase over the previous intake manifold. The engine’s rear-wheel horsepower peaked at 946 with the Holley Hi-Ram installed.


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 baseline intake manifold consisted of a ported Holley SysteMAX lower intake, which was all the rage in NMRA Renegade during its formative years. A Cartech box intake replaced the long-runner Holley SysteMAX upper.

Here is a comparison of the lower intake manifolds, with the Hi –Ram towering over the low-profile SysteMAX.

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.

Dez Racing’s Brian Machie tapped an additional hole for another vacuum hose fitting to go along with the LS-style MAP sensor and second vacuum-line fitting.

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.

Mike Dezotell also removed the distributor for the intake installation and it’s important to note that the side-entry lid allows the use of regular height distributor.

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!

Machie verifies that the Hi-Ram ports line up with the cylinder head’s intake ports, which they did without any issues.

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.

Machie verifies that the Hi-Ram ports line up with the cylinder head’s intake ports, which they did without any issues.

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.

A Vibrant rubber elbow worked really well, but we ran into a problem with aluminum piping. Charron used band-clamps to connect each pipe when he originally built the system, making it rigid and well built. But the new angle of the throttle body caused a misalignment of the pipe going into the fender.

Charron carefully measured twice and cut once when he made the adjustment to the charge pipe and it fit perfectly.

Dezotell kept the timing curve identical for the intake testing and the engine saw 24 degrees for its maximum timing. The noted tuner and racer said that the fuel consumption increased dramatically, showing the engine was making great power, perhaps even more than what showed up in the final results.

The ProCharger F-1A-94 produced a stellar 29 pounds of boost with the old intake setup and the better flowing Holley Hi-Ram dropped that down to 27.1 psi. The blower pulleys remained untouched to ensure a true A-B comparison test.

Holley offers many different configurations of its Hi-Ram intake manifold like this lid that allows the use of two carburetors or twin throttle bodies. They also sell blank ones for those who want to get creative with the induction setup. The aftermarket is also ramped up with several lids for dozens of applications.

The iconic, forward-facing lid is available and it accepts up to a 105mm LS-style throttle body, which can flow enough air for most applications. Small-block Ford applications that rely on the front-mounted throttle body must run a low-profile distributor or individual ignition coils. Holley offers two options for distributors—Sniper Hyperspark version (PN 565-322) and a Holley EFI Dual Sync distributor (PN 565-211). If you opt for an ignition coil conversion, MSD sells a really nice Sync Plug—PN 85221 for 289/302 applications and 351Ws use PN 85061.

Dez Racing
(508) 336-6588

Holley EFI
(866) 464-6553