As the saying goes, no man is an island. In the world of engines, the same time-honored adage applies. No single component exists without affecting those around it, and selecting parts that not only work well with each other, but deliver the appropriate performance for the engine’s intended usage is key, to a perfect power plant.

Intake manifolds and their respective throttle assemblies are one of the big three components– the other two being cylinder heads and camshafts– that play the biggest role in not only how much power an engine produces, but in how it’s delivered. There are countless intake manifolds available in different styles, for various engine architectures, and for radically different applications across the Holley product line. To illustrate just how drastically choosing the right one is, we put three of our most popular manifolds to the test on the dyno at Westech Performance.

The Test Mule

The test mule for this dyno session was a 440ci LS7-based engine that was built to run on E85. It features 13:1 compression, Holley EFI, and a fully CNC'd top end.

"There’s no discounting the popularity and proven performance of the LS engine architecture, so for this test we recruited a freshly built 440ci, LS7-style engine. This engine was built to run on E85 so it uses a 13:1 compression ratio, an LS7 style cylinder head and a robust valvetrain capable of over 7,000 rpm. The ignition system consisted of MSD, LS-style coils, a Mr. Gasket electric water pump supplied dyno coolant, and the exhaust consisted of a pair of Hooker stainless steel headers."

The intakes set to be tested were a Holley Hi-Ram with dual 4150 throttle bodies, dual 4500 throttle bodies, a front feed plenum, and MSD’s popular Atomic AirForce polymer intake. Each of these intake configurations represents a popular combination used for a wide range of racing types, so putting them all on the dyno with the same engine would paint a very clear picture where each of them shines.

Holley Hi-Ram with Dual 4150 Throttle Bodies

First up we installed a Holley Hi-Ram intake manifold with a dual 4150 plenum and twin 4150 throttle bodies. Each throttle body flows 1000 cfm.

The Holley Hi-Ram is an incredibly versatile intake manifold. In LS configuration, it is available for LS1, LS2, and LS6 cathedral port heads, LS3 heads, and LS7 heads (used here). The intake is available with multiple plenum tops and even blank tops are available for completely universal applications.

For the first test, we topped the Holley Hi-Ram intake manifold with a dual 4150 plenum. This plenum is compatible with carburetors or EFI throttle bodies, however the latter was used since this engine is fuel injected. Each throttle body (PN 112-577) flows 1000cfm, giving the engine a total of 2,000cfm of potential breathing room.

With the induction combo synched up, Westech’s Ishmael Candia worked the keyboard for the Holley Dominator EFI system, while dyno master, Steve Brulé, pulled the throttle. In this configuration the engine grunted out 747hp and 621lb-ft of torque. This induction setup delivers massive power, near instantaneous throttle response and is ideal for a dedicated drag-race setup.

Holley Hi-Ram Dual 4500 Throttle Bodes

For the next test, the intake plenum was replaced with a 4500-style plenum (PN 300-223) and two, 4500-style throttle bodies were installed (PN 112-578).

To test out the theory of more is never enough, we replaced the plenum lid of our Hi-Ram with a 4500-style top. Compatible with either Dominator carburetors or 4500-style throttle bodies, such as the one we used (PN 112-578) this top offers massive airflow to the tune of 4,000cfm (with throttle bodies). While in theory the 4150-style intake should have been more than enough airflow to feed the 440ci LS, the dyno tells its own story.

With twin 4500 throttle bodies, the engine generated its highest horsepower of the day at 754hp and 624lbft of torque. While, in theory, the smaller throttle bodies should have been able to supply all the airflow the engine could want, Brulé attributes the power increase to the placement of the throttle body bores. With the 4500’s wider footprint, the 8 butterflies are more in line with each cylinder bank’s intake ports and that likely had an effect on overall power.

One of the things Brulé cautions is that due to the immense amount of throttle blade area, the drivability of this combination wouldn’t be near as good as the 4150 setup, or a smaller, single throttle blade. However, in a drag racing application, there is no disputing the clear power advantage.

Single Throttle Body Front-Feed Plenum

Holley's single throttle body plenum (PN 300-246), complete with Holley 105mm throttle body is a very popular combination that makes great power and is perfect for power adder applications.

For the next test, we unbolted the 4500 plenum and moved to a single throttle body, front-feed plenum (PN 300-246). This plenum is hugely popular with LS enthusiasts and is a great option for naturally aspirated and boosted applications. For the first test, we equipped it with a 105mm Holley EFI billet throttle body. This throttle body flows a huge amount of air and is an upgrade form the standard GM 90mm throttle body. On the dyno, it delivered 732hp and 606 lb-ft of torque. While a 22 horsepower drop from the dual 4500 throttle bodies, this setup offers a much more progressive throttle opening that will deliver significantly improved drivability compared to either of the dual-quad throttle bodies. Brulé attributed the slight horsepower dip to both the lower airflow of a single throttle blade as well as plenum volume and the position of the throttle blade in relation to the intake ports.

The added airflow of the dual throttle bodies makes a clear difference throughout the dyno pull. The 105mm, single throttlebody is close, but can't match the added airflow.

MSD Atomic AirForce with Billet 105mm Throttle Body

MSD's polymer intakes are a great option for dual purpose cars and generate an extremely wide power band.

For our fourth and final intake combination of the day, we utilized an MSD Atomic AirForce intake. This a radical departure from the cast aluminum Hi-Ram intake and uses a high-tech polymer construction, which makes this intake manifold extremely light, and have excellent heat rejection properties. It also has slightly smaller, very long runners that allow it to deliver a wide powerband perfect for dual purpose cars, road course racers and more. On the dyno, the Atomic delivered a peak or 718hp and 621 lb-ft. While that might seem like a huge power tradeoff, with 36 ponies missing from the 4500 test, the average horsepower (power across the entire RPM range) was better than every other intake tested. For a dedicated drag race vehicle that operates in a very narrow RPM range, the AirForce wouldn’t be the best choice, but for a dual-purpose vehicle that operates in an extremely wide powerband, it would work like a charm.

Note how the AirForce intake generates significantly more torque than the Hi-Ram and only falls off at high rpm. The average horsepower of this intake was the best of our test and outside of a dedicated drag car, this is an easy choice.

This graph shows each manifold and is a very clear picture as to where each sines. One thing the dyno won't show is drivability. The single throttle body plenum is going to be the most docile at low revs and part throttle whereas the dual 4150 and dual 4500 throttle bodies are going to be touchier.