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Holley EFI's 351W Hi-Ram Intake Manifold Will Let Your Windsor Build Breathe Deeply

By: Wes Duenkel | Photographer: Bryan McTaggart | 07/23/2021 < Back to Motor Life Home

When it comes to Ford Windsor V8 small-blocks, the near-ubiquitous five-liter has hogged most of the limelight over the years. But what about the folks who’re looking for big displacement and big power from Ford’s venerable pushrod power plant? While it might be slightly less prevalent throughout enthusiast and racing circles, the 351W is undoubtedly a stout piece in its own right, making it an attractive option for folks who’re looking to build motorsport-caliber combinations while retaining much of the old-school vibe offered by the legendary platform.


300-242 studio shot 1

The Hi-Ram’s design puts a modern twist on the old school tunnel ram design.



With that in mind, a few years ago Holley set to work on an effort to bring fuel injected 351W-based engines into its Hi-Ram intake manifold lineup. “This manifold actually grew out of the program for LS Hi-Ram series,” says Jim Dralle, senior design engineer for Holley Performance. “We’d finished the work on the LS3, cathedral port, and LS7, and we felt that the 351W builders could use some more options here, so it seemed like a natural progression.”


Dralle notes that the folks building potent 351W-based engines tend to gravitate toward a more specific niche of the market than the LS stuff does, though, and those circumstances helped guide the overall approach to this manifold’s design. “It’s generally the hardcore racers. There is some street stuff, but I think when you look at classes like NMRA Hot Street from back in the day, there’s a lot of 400+ cubic-inch Windsors out there that live at the strip.” And those racers tend to choose combinations like these out of preference rather than necessity, so Holley sought to compliment these potent, high-winding mills with a manifold that could keep up.


Fox Mustang launch

Ford’s Modular V8 platform gets the lion’s share of attention these days, but big-cube Windsor small-blocks are incredibly popular with racers looking to make serious pushrod power.


Development


Similarities between the LS cylinder head and the popular high performance Ford Windsor heads on the market allowed Holley to hit the ground running when prototyping this new intake manifold, but there were also a number of Windsor-specific considerations that needed to be sussed out along the way.


“The biggest challenge with the 351W EFI Hi-Ram development was dealing with all the stuff that isn’t on an LS engine,” Dralle explains. “Having to deal with a distributor, a water outlet – addressing packaging concerns became a priority early on.”


Fortunately, modern engineering technologies make this aspect of the development process much less of a trial-and-error proposition than was in decades past. “Everything we do is fully solid modeled in software like Creo or Solidworks,” he tells us. “That provides us with very tight control on the part design. And with that we can not only create models of things like this intake manifold, but also associated parts – like the distributor it needs to work with – so we can ensure the packaging works the way we want it to.”


300-242 water neck

Engineers needed to make provisions for small-block Ford-specific hardware, like the distributor mounted just in front of the intake.



It also allowed engineers to deliberate on which features it made sense to include. “We talked about whether or not to do a water neck, for instance. In the end, we decided that the way to make it as useful and user-friendly as possible to the most people was to put a water neck in, rather than opting for more of a race-only kind of setup. It makes the casting more complex, but the benefit is that the guys running a more standard radiator hose setup will be able to hook up to it easily.”

Design

Dralle points out that, unlike Ford’s factory 351W EFI intake manifold, the Hi-Ram is designed for a performance application from the ground up.


“The factory manifold was intended for trucks and sport-utilities, and some of the aftermarket stuff is based on that design. It’s a long runner manifold built to provide lots of low-end torque, and it’s going to limit engine speed where you’re going to make power. Those manifolds rarely make power above 5500 RPM, and that’s because of the engine applications that it was originally designed for – you’re tuning to a given torque curve that you want at a certain engine speed range. And of course, as performance goes up, those limitations become more obvious.”


300-242 side profile

These straight, beefy runners provide an unobstructed path into the heads, just as the horsepower gods intended.



The Hi-Ram intake, by contrast, employs a very different design approach. “In many ways, it’s very much like your traditional tunnel-ram type drag racing manifold that would have had a pair of carburetors on top of it,” Dralle says. “You’re going to a central plenum, runners that are fairly straight, and as few flow restrictions into the runner itself as possible. The plenum designs also have to be such that we’re not creating problems with things like recirculation – with an EFI lid, that’s much more an issue that it would be with something like a traditional two-carb setup.”


With the Hi-Ram, Holley is also not limited by some of packaging constraints that an OE-style manifold must adhere to.


“The factory is trying to make peak torque at, say, 3000 RPM, and then you’re trying to figure out how to package eighteen inches of runner and make it fit under the hood. The Hi-Ram is the opposite – we using a shorter runner, and we’re trying to make it as direct as possible. The engines that this manifold is going to be used on are likely to make peak torque at 5000 to 6000 RPM, and they’re going to make peak power above 7000 RPM. Those considerations helped us to flesh out the rest of the design. There comes a point with a race manifold where you’ve kind of got to say, ‘let’s focus on the performance, and worry a little less about the packaging.’ There’s also just that fun factor of seeing something as racy looking as a Hi-Ram on top of an engine, too.”


300-424 runner tops

Along with the performance on offer, the Hi-Ram makes the kind of visual statement that’s rare to see on fuel-injected power plants.


Applications

Another cool aspect of the Hi-Ram design is the modularity it provides – builders have several choices in plenum tops, and Holley now also offers side-entry lids that allow for plumbing similar to a typical five-liter.


“There are also a lot of guys who plumb from the firewall side who’re running the big ‘ice chest’ intercoolers that are mounted in the car,” Dralle notes. “It all just depends on what you want to do – we have plenum tops that’ll take two 4150s or two 4500s, as a carburetor or as a throttle body. A friend of mine runs two throttle-by-wire LS throttle bodies on top of a blank top in his Cougar – you can configure whatever you want, really.”


In terms of ideal combinations for this manifold design, he’s quick to cite legitimately potent builds. “Something along the lines of a 400 cubic-inches or more that makes peak power above 7000 RPM.” But while that might lead you believe that this manifold is purpose-built for naturally aspirated engines, Dralle points out that they haven’t forgotten about the power adder crowd here, either.


300-242 nitrous boss

The Hi-Ram is ready for spray, right out of the box. Nitrous bosses are built-in below the injector ports. Just drill, tap and prepare your 351W for a shot of the good stuff.



“We definitely envisioned folks would use power adders with this manifold, whether that’s a centrifugal blower, turbos, or nitrous. A modular design like this really lends itself to a ‘sandwich’ type of setup. We’ve also got a nitrous boss down by the injector if you want to run it right at the port.”


Designed to work with any 9.5” deck Windsor motor, Holley’s Hi-Ram 351W EFI manifold is mainly intended to be paired up with an aftermarket performance cylinder head, but it can be made to play nice with the factory heads, too. “You may need to do a little trimming along the top of the manifold flange if you’re using a stock iron head,” Dralle says. “It’s designed to not preclude a factory iron cylinder head, but at the same time the material there and the flange configuration here are geared toward an aftermarket performance cylinder head.”


Along with the 9.5 deck Ford Windsor Hi-Ram EFI intake manifold, Holley Performance also introduced an 8.2" deck Ford Windsor Hi-Ram EFI intake manifold at SEMA 2019, bringing the same modularity and motorsport-bred design benefits to the 289/302ci small-block Ford crowd. Both versions of the manifold are available now.

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