Recently, we took an in-depth look at the electronics Holley came up with to run an electronically fuel injected engine. If you recall, their Dominator “software” (and ECU) is a pretty cool mix of sophistication and user friendliness. Basically, it allows folks like us (with a wee aversion to electronics) to adapt to EFI easily and actually rather seamlessly. Fair enough, but isn’t there a huge laundry list of hardware you need to properly operate an electronic fuel injection system? Maybe less than you think. What follows is the beginnings of a four part series on EFI Hardware; we’ll begin with the obvious, and that’s the intake manifold:
Holley’s modular Hi-Ran intake manifold was originally designed as a cost effective alternative to fabricated sheet-metal manifolds. Induction system height wasn’t really a criteria (they decided that in maximum effort high-performance applications, induction system height should not be limited). This meant the Hi-Ram was, for all intents and purposes, engineered as a modular tunnel ram that accepts an EFI throttle body as well as various carburetor tops. The modular arrangement allowed the Hi-Ram to be manufactured for all of the common LS-style Chevrolet cylinder head port arrangements (LS1/LS2/LS6; LS3/L92; LS7). It also meant that various different interchangeable tops could be offered: Dual 4500 series carburetor, Dual 4150 series carburetor, EFI and finally, a blank that you can modify to fit a specific need.
Fair enough, but as you can well imagine, this took a serious amount of engineering time to get right. And then you have to mix in the fact that the setup had to function in myriad applications (drag race, muscle car, marine, off-road, sand rails, pulling trucks, track, street-rod applications, etc.) and you can see that it wasn’t exactly easy. While they were at it, they wanted to build an aggressive looking piece too, but that was definitely a form-follows-function part of the equation. Once they determined the appropriate dimensions, the looks part pretty much fell into place.
The manifold base(s) and interchangeable tops are cast from aluminum. As pointed out above, the base is designed to be modular in configuration to accept a wide range of carbureted and EFI tops and at the same time, to prove attractive to builders and fabricators as the foundation for custom induction systems. In the case of our same LS3 intake, the specs are as follows:
- Base Plenum Top Mounting Flange Height – 8.42-inches to the lifter valley cover flange on engine block.
- Total Height with 92/102-mm EFI Plenum Top – 12.32-inches to the lifter valley cover flange on engine block.
- Port Size – 2.49-inches Height x 1.21-inches Wide
- Mounting Flange Gasket Type – Standard LS3 Molded O-Ring
- Plenum Top Gasket Type – 3/32-inch Round O-ring Cord
- Throttle Body Flange Location, with 92/102-mm EFI Plenum Top :
- Height – 8.42-inches (from engine block lifter valley cover flange),
- Longitudinal Location – 3.84-inches (forward from engine block front flange), Angle – 25 degrees (down from vertical)
- Runner Length – 6.50-inches, As-Cast Runner Cross-Sectional Area – Tapered 4.25 in² to 2.77 in²
According to Holley, “the EFI fuel rails are machined for -8AN O-ring fittings with passages large enough to accommodate high fuel flows and dampen pressure pulsations in the fuel system and come standard with EFI Hi-Ram kits.”
Holley points out that the intended for use if for normally aspirated or forced induction engines in the 6.0 to 7.0+ liter range, with maximum power produced at 7000-8000+RPM. In other words, it’s the right manifold for a big power LS style engine.
In the next segment, we’ll take a look at Holley’s new high flow throttle bodies. Watch for it.