Tech Stuff

Intake Manifolds

It's What is On the Inside That Counts

Words by Todd Silvey

Photos by Todd Silvey and courtesy of Holley Performance Products

New from Holley Performance is their Sniper line of mass-produced fabricated sheet metal intakes. The advertised power band for these intakes is an impressive 1800-7000 RPM. Out of the box, the sniper intake weighed in at a mere 11.2 lbs. compared to the 22.5 lbs. cast aluminum intake we are replacing.


Intake manifolds are an amazing application of shapes, sizes, and airflow theory that can make or break your specific racing engine package. Now you might resort to getting the best deal on the intake that matches your RPM-zone and be done with it. I invite you to read a little bit into the theories of flow, plenum size, runner design and get a bit more savvy on your own induction system.


What prompted this article was looking over the new mass produced and reason-ably priced sheet metal intakes that Holley Performance has debuted called the Sniper sheet metal fabricated intake manifold. When I was looking over the specification sheet, I noticed what most racers call the "power band" for the new intake design is rated at 1,800-7,000 RPM. This is a noticeable difference between most any cast aluminum intake that has a typical 5,000 RPM range, whether it be from idle to 5,000 RPM or 1,500 to 6,500 RPM range in general.


With this unique data, we spoke to Ty Peek from Holley Performance Products about the new Sniper line of intakes. "For example, the cast aluminum intake manifolds for the small block Chevy or Ford pretty much has the same general design, short of some minute changes, as intakes from the '60s and '70s'" Peek continues. "Going to a sheet metal intake design from a cast manifold, what you get is obviously a lot more plenum volume, and much greater ability to route the runners the way you want. This is where we developed the new Sniper with a broad RPM power band."


Many intake shapes and sizes basically utilize two different components, the intake runners and an intake plenum mentioned by Peek. Varying runners and plenums provide different results depending on if you are all-out racing or a general performance application. Since this is Drag Racing Online magazine, we're concentrating on intakes for the 'strip.


The plenum is the cavity beneath the carburetor or injectors where atomized fuel/air is transferred from the inlet to the intake runners. Hardcore cast aluminum race intakes use a single open plenum. This design promotes an equal distribution from the plenum to the cylinders. A more street oriented performance intake uses a dual place design which manipulates the plenum area with staggered and/or split feed to the intake runners. This design works well in a low RPM application where drivability is needed. But, compared to an open plenum intake, the dual plane design runs out of its performance band in the typical 4,500 to 5,000 RPM range.


A single-plane intake has a shorter and direct runner to the heads which results in higher amounts of air from the induction area to the heads. That makes single-plane intakes perfect for higher RPM and horsepower. As we inspect the new Holley Sniper intake, we see a unique V-shaped plenum available with single or dual carburetor/style flanges. With this plenum design comes extreme short sheet metal intake runners that rely on the plenum to create a path to each cylinder head intake port.


"The combination of runner length and plenum design is a big part of the ex-tensive R&D that has been invested in this intake," Peek tells us. "Racing engines, in general, have progressed from 65 to 80% volumetric efficiency to engines today achieving upwards of past 120% volumetric efficiency. The research on our Sniper intake has been going on for a good while now and finding that combination that works as a good general race intake has been an accomplishment."


In racer/nerd speak, a simplistic description of volumetric efficiency (VE) is the ability for the engine to move the charge of fuel and air into and out of the cylinders. This VE ratio makes the measurement very critical related to the intake manifold. The sizable V-shaped plenum and very short intake runners help with that efficiency. Aggressive racing cam profiles full of lift and intake/exhaust valve overlap can cause air charge pulses back into the plenum called reversion. With a smaller plenum on cast aluminum intakes compared to the Sniper, this reversion can alter the flow of air/fuel to other cylinders at high RPM.

Scaling in at half of the weight of the cast aluminum manifold removed from our 498c.i. big block Chevy, the Sniper intake lined up and bolted on with no surprises. The overall height of this intake is actually no taller than our valve covers. Massive R&D on the Holley Performance dyno is what gives the short intake runner design and low V-shaped plenum its very broad power band.

Two critical configurations of all intake manifolds give them their performance characteristics. The intake runners and an intake plenum are very different. The Weiand Street Warrior intake (left) features small size and long runner lengths by means of a split height plenum.  This provides street drivability from idle, but only has a power band to the 4,500-5,000 RPM range. The Weiand Track Warrior intake (right) has a much higher RPM power band (3,500-8,000 RPM) due to its large and flat plenum combined with tall and narrow intake runners that gradually spread to match the cylinder head port design.


"We've always got engines on our dynos constantly running every day," Peek explains. "Some of the new trends in development seems to be a taller, narrower intake runner design like the Track Warrior intake from Weiand. A taller, narrower port where the plenum meets the intake runners gradually changes to the cylinder head port shape. This development has made strides in solving reversion and atomizing the air/fuel mix. That has netted us some horsepower gains for the cast aluminum intake market."


The Sniper intake is available for standard deck blocks such as the 482c.i. big block Chevy bracketeer we are outfitting. We note the intricate TIG welds that fuse the 1/8-inch thick T6061 sheet aluminum plenum and runners together. The intake manifold flange is a heavy 3/8-inch thick. Other provisions like two 1/2-inch NPT gauge ports, thermostat housing, and distributor mounting area are beefy and carefully fabricated as well. We have held many lighter "race weight" sheet metal intakes in the past, but the Sniper seems to be built for durability as much as form and function.


Holley also has Sniper models for EFI throttle bodies as well as entirely different models constructed with even thicker T6061 sheet aluminum construc-tion for high horsepower, nitrous, and boosted applications. There is a spread of part numbers offering provisions for EFI injectors along with an accessible bolt-on panel on the top of the plenum.

The fabrication workmanship in the new Sniper sheet metal intakes is impres-sive. The manifold face is made from 3/8-inch thick T6061 aluminum while the runners and plenum are constructed as well of 1/8-inch thick T6061 aluminum. The welds are broad and strong and heavy materials surrounds the NPT cooling ports, carburetor flange, and distributor mount.

Each bolt face for the intake/cylinder head bolts is pocket machined to match performance intake bolt head flanges. While we chose the black powder coated Sniper intake, they are also available in a polished aluminum finish. The Holley Sniper intakes available to accept single and dual carburetors along with EFI throttle bodies. Holley invested a lot of R&D hours into the “injector phasing” of their Sniper EFI intakes. This phasing is the exact point where the injectors are located in relationship to the intake manifold pulse.


The racer trend towards electronic fuel injection is another source of improving intake technology specifically for those applications. Ty Peek describes, "What we see there is the development of what we call injector phasing for intake manifolds. We are getting the injector to spray with the right location point on the intake and injector timing related to the intake manifold pulse. An EFI injector may be atomizing the fuel already, but if we get the positive pressure behind the intake valves at the injectors, you get an air/fuel atomization that is basically zero percent fluid."


Keep looking at the new options in intake manifolds for your specific race application; you might be surprised that technology in plenum and runner R&D might be a bolt-on improvement. 


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