Sized to Rise: LS Throttle Body Test

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This two-piece, CNC-ported, single-plane intake from Mast Motorsports offered amazing performance, but only after we got it enough air.

Words and Photos By Richard Holdener

If we believe the age-old adage that our beloved internal combustion engine is nothing more than a glorified air pump, we must also believe in the simple philosophy that more air must be better. From the most basic standpoint, increasing the power output of any motor requires nothing more than improving the airflow though the system. It is important to understand the distinction between airflow through the system (meaning the motor) and simply increasing the airflow of one individual component. More intake, head, or even (in our case) throttle body flow may or may not increase power. The question is can the motor utilize the additional airflow supplied by the component or is there another restriction elsewhere in the system?

Extreme examples make this easier to understand. A throttle body (or any other component) capable of supplying airflow to feed 900 hp will be of limited use on a 450-hp (stock) motor and may not show any power gains at all. The problem is not in the flow rate (or quality) of the component tested, but rather in the engine combination itself.

Of course, there are also times when simple airflow devices show impressive power gains. This test run with throttle bodies on our 427 LSX was a perfect example where more airflow offered more power. The test was run on our familiar 427 LSX short-block, but we made changes to the induction system. The 427 itself featured the 4.125-inch bore GM LSX iron block supplied by Gandrud Chevrolet. The freshly machined block was stuffed with forged internals from Lunati, Carrillo, and CP, not to mention components from Total Seal, Moroso, and a cam from Brian Tooley Racing. The additional components included an ATI Super Damper, COMP Cams front cover, and Meziere electric water pump.

Having already run both cathedral-port and LS7 induction system, we decided it was time the LS3 boys got some love. To that end, we installed a set of Black Label LS3 heads from Mast Motorsports, topped with one of their impressive CNC-ported single-plane intakes. Having run their systems in the past, we were excited about testing them on our 427.

Based on the specs, the Mast Black Label LS3 heads looked impressive. In fact, the 427 might not have been enough motor to take full advantage of the airflow offered by the heads (or intake), but we knew we at least had enough to make some real power. The Mast LS3 heads featured 280cc intake ports that offered 390 cfm, or enough to support 800 hp (or more) on the right application. The amazing flow potential can be attributed to a combination of the 2.20/1.6 valve package and full CNC porting. The finish quality was excellent, and the Mast heads have always proven powerful in previous testing. The heads also featured exhaust ports that flowed 249 cfm, 70cc combustion chambers, and .750-thick deck surfaces — making them a great choice for forced induction applications. The heads were supplied with valves only, which we finished up with a valve spring package from Brian Tooley Racing. The Mast heads relied on larger-diameter valve guides, requiring a set of 4682-16 spring seats to work with the BTR spring package. The Mast heads were secured using ARP head studs and Fel Pro MLS head gaskets.

Topping the Mast LS3 heads was one of their single-plane intake manifolds. The two-piece designed allowed full CNC porting and, like the heads, was a serious piece of engine porn. Mast offered intakes for the all three LS engine families (cathedral-port, LS3, and LS7), as well as with 4150 and 4500 carb flanges. Adding to the mix was the availability to run EFI (with injector bungs) or simply as a carbureted intake. We ran one of their LS7 version previously on a 495-inch motor to the tune of 810 hp, so we know these intakes are capable of serious power. We chose a 4150-flanged EFI version for our 427. The injected combination was run with a set of 83-pound Holley injectors using a FAST XFI/XIM management system. Also present was a set of Hooker 1 7/8-inch headers feeding collector extensions (but no mufflers), 1.8-ratio LS7 rockers, and a remote K&N oil filter.

First up was the 4150 throttle body from FAST. With the throttle body in place, we ran the 427 in anger to the tune of 669 hp at 6,600 rpm and 574 lb-ft at 5,300 rpm. We expected more power output from the Mast-headed combination, so we went looking for the culprit. Thinking the 4150 throttle body might be limiting airflow, we decided to step up our game with a larger 4500-series throttle body. All we needed was the 4150-4500 adapter to mate the larger throttle body to the 4150 flanged intake. Speedmaster came to our rescue with just such an adapter.

Run with the larger throttle body, the Mast-headed LS3 produced 681 hp at 6,600 rpm and 578 lb-ft of torque at 5,200 rpm. Obviously, the Mast intake required more flow to feed the needs of the LS3-headed 427.

Run with the larger throttle body, the Mast-headed LS3 produced 681 hp at 6,600 rpm and 578 lb-ft of torque at 5,200 rpm. Obviously, the Mast intake required more flow to feed the needs of the LS3-headed 427.

Throttle Body Test-4150 vs 4500 (Mast 427 LS3) As is evident by the power curves, the Mast-headed 427 LS3 was in dire need of additional flow. Despite being flanged (and sized) to accept a 4150 carburetor or throttle body, the Mast single-plane intake wanted more airflow than the 4150 throttle body could supply. Equipped with the 4150 throttle body, the power leveled off at 669 hp at 6,600 rpm. After installation of the 4150-4500 carb adapter and 4500-series Accufab throttle body, the power output jumped to 681 hp at 6,600 rpm. Note the majority of the gains occurred higher in the rev range; this is typical of improvements in airflow.

Throttle Body Test-4150 vs 4500 (Mast 427 LS3)
As is evident by the power curves, the Mast-headed 427 LS3 was in dire need of additional flow. Despite being flanged (and sized) to accept a 4150 carburetor or throttle body, the Mast single-plane intake wanted more airflow than the 4150 throttle body could supply. Equipped with the 4150 throttle body, the power leveled off at 669 hp at 6,600 rpm. After installation of the 4150-4500 carb adapter and 4500-series Accufab throttle body, the power output jumped to 681 hp at 6,600 rpm. Note the majority of the gains occurred higher in the rev range; this is typical of improvements in airflow.

After installation of the 4500-series Accufab throttle body, the power output of the Mast-headed 427 rose to 681 hp at 6,600 rpm and 578 lb-ft of torque. As expected of a flow restriction, the gains offered by the larger throttle body were most prevalent at the top of the rev range (where airflow is most critical). The simple throttle body upgrade netted an additional 12 hp. That the power came with no change in intake shows the 4150-flanged Mast intake still had more to offer. Now, all we need is more test motor!

Sources: ATI, Atiracing.com; ARP, Arp-bolts.com; Brian Tooley Racing, Briantooleyracing.com; COMP Cams, compcams.com; CP Pistons/Carillo Rods, Cp-carillo.com; FAST, fuelairspark.com; Gandrud Chevrolet, parts@gandrud.com; Holley/Hooker/NOS, holley.com; Lunati, Lunatipower.com; Mast Motorsports mastmotorsports.com; Moroso, Moroso.com; MSD, Msdignition.com; Speedmaster, Speedmaster79.com.

About Elizabeth Puckett

Elizabeth Puckett is a seasoned writer and hardcore gearhead. She was born with motor oil in her blood and a passion for everything that goes fast.