Was our decked-out 427 LSX stroker enough motor to take advantage of what the Mast single-plane intake had to offer?

Words and Photos By: Richard Holdener

When it comes time to choose an intake manifold, the application and intended usage (purpose) is every bit as important as the intake itself. Even the best intake manifold is next to useless if applied to the wrong application. Much like camshafts, intake manifolds cannot be all things to all people, or in this case, all applications. A cam that works well on a stock motor will not likely do so on a dedicated race motor. The same holds true for an intake manifold.

Intake designs are optimized for specific engine speeds. The displacement somewhat alters this effective operating speed, but an intake designed for high-rpm power production will be less than ideal at lower engine speeds. This doesn’t make it a bad design, it just makes it wrong for a mild combination. The same can be said of running a stock intake on a race motor, as peak power production will suffer. This test on the impressive single-plane intake from Mast Motorsports clearly illustrates the changes in power offered by different intake designs.

Given the importance of the test motor, we decided to run this comparison between the stock LS7 and Mast Motorsports intakes on something other than a stock LS7. Though plenty powerful in stock form, the stock LS7 would certainly favor the stock intake. The same can be said of a dedicated race motor or massive stroker, as this combo would certainly favor the Mast design. To illustrate the gains offered on a more conventional combination, we chose our 427 LSX test mule, dubbed the Magnificent LS7.

Starting with an LSX block from Gandrud Chevrolet, we combined a Lunati crank with CP pistons and Carrillo rods. Brian Tooley Racing supplied the Stage IV LS7 cam, while COMP Cams came through with hydraulic roller lifters, pushrods, and a trick, aluminum front timing cover. The TFS Gen X 260 LS7 heads were secured using ARP head studs and Fel Pro MLS head gaskets. Moroso stepped up with a complete (wet sump) oiling system full of Lucas 5W-20, and ATI dialed in the rotating assembly with a Super Damper. Finishing touches included a set of FAST injectors, 1 7/8-inch Hooker headers, and a Meziere electric water pump.

Though the supplied Mast intake allowed us to run it in fuel-injected form, we decided to spice things up and run it carbureted. Not only would we be comparing the two different styles of intake manifolds, but we would throw in carburetion versus fuel injection to boot. To establish our baseline, we set up the Magnificent LS7 first with the stock fuel-injected intake. Sporting the FAST 75-pound injectors, the injected LSX was dialed in using a Holley HP management system. This system would also be employed to run the identical timing curve on the carbureted Mast intake. The factory LS7 intake was fed by a 90mm Holley throttle body.

After dialing in a consistent air/fuel mixture to 12.9:1, the LS7 intake produced peak numbers of 641 hp and 571 lb-ft of torque. Thanks to the long-runner design, torque production exceeded 550 lb-ft from 4,400 rpm to 6,000 rpm and more than 500 lb-ft from 3,800 rpm to 6,700 rpm.

The factory LS7 intake offered a pretty impressive combination of power and torque on this LSX combination, but we suspected there was more power to be had from the right intake. The single-plane intake from Mast Motorsports featured a two-piece design that allowed full CNC porting. Everyone present at Westech during testing was more than a little impressed by the finish quality of the intake. It was the kind of part you want to sit up on your shelf and just show off to friends, rather than install and get fuel stained.

Available with either a 4150 or 4500 carb flange, we stepped up to the big boy Dominator. Though we ran this test in carbureted form with a Holley 1050 Ultra Dominator, the intake was also set up for EFI use with injector bungs and fuel rails.

Run with the Mast single-plane intake and Holley 1050 Ultra Dominator, the 427 produced 666 hp at 6,700 rpm and 582 lb-ft of torque at 5,100 rpm. Torque suffered below 4,700 rpm (partially due to air/fuel), but the real culprit was the significant difference in runner length. Having exceeded 800 hp with this intake on a wilder 495 stroker, we know this 427 was just scratching the surface of its potential.

We simply plug the holes using a set of injectors, but all fuel came courtesy of the Holley Ultra Dominator.

Equipped with the Mast intake, the peak numbers jumped to 666 hp at (the same) 6,700 rpm and 582 lb-ft of torque at 5,200 rpm. Both peak power and torque were up with the Mast intake, but the stock manifold did offer improved torque production below 4,700 rpm. Having exceeded 800 hp with this intake on a large-displacement, stroker combination, the gains on this test were more a function of a lack of test motor than lack of ability on the manifold.

427 LS7 Intake Test-Stock vs Mast Single Plane
As expected of the impressive Mast intake, the single-plane easily bested the stock LS7 intake for peak power. In fact, the Mast intake offered both more peak power and peak torque than the stock manifold, but the different designs excelled at different engine speeds. The long-runner, factory intake offered improved torque production below 4,700 rpm, but lost out to the Mast intake above that point. What the Mast intake really needed to strut its stuff was more displacement or engine speed, or both. Run previously on a 495 stroker, we easily exceeded 800 hp with the impressive piece.

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, [email protected]; Holley/Hooker/NOS, holley.com; Lunati, Lunatipower.com; Mast Motorpsorts, mastmotorsports.com; Moroso, Moroso.com; MSD, Msdignition.com; Trick Flow Specialties, trickflow.com