Holley Dual-Plane: 471 ft-lbs @ 4,300 rpm
Holley Single-Plane: 463 ft-lbs @ 5,200 rpm
Largest Gain: 54 ft-lbs @ 3,500 rpm
In terms of torque production, there really was no contest. Even though peak torque production differed by just 8 ft-lbs, the dual-plane offered gains that exceeded 50 ft-lbs down low. The additional torque offered by the dual-plane in the low- and mid-range is why it is usually chosen over the single-plane for most street applications. I even tested the dual-plane design under boost on a cathedral-port LS application with excellent results. If it’s better naturally aspirated (NA), then it’s better under boost!
Test 2: FAST LSXR vs Mast Carbureted Single-Plane
This test offered a comparison between a long- and short-runner intake design. In fact, I used nearly the same 468-stroker test engine to compare the Mast single-plane intake to the FAST LSXR LS3 manifold. The 468 featured a Darton-sleeved block stuffed with a Lunati crank and rods teamed with JE forged pistons. Unlike the previous test, the 468 was topped with Mast black-Label LS3 heads.
The combination also included factory LS3 rockers, Comp hardened pushrods, and Kooks 1⅞-inch stainless headers. Also present was a Milodon oil pan and windage tray, Meziere electric water pump, and FAST 75-pound injectors. The finishing touch was, of course, the FAST LSXR LS3 intake manifold and 102-mm Big Mouth throttle body. Equipped with the FAST LSXR intake, the 468 produced 732 hp at 6,400 rpm and 665 ft-lbs of torque at 5,200 rpm.
After running the FAST intake, I replaced the EFI system (FAST XFI/XIM) with the Mast single-plane intake. The Mast intake featured a two-piece construction, which allowed them to fully CNC port the internals. This thing was a work of art; the kind you hate to install and get dirty.
The Mast intake was flanged to accept a 4500-series Holley carburetor. To feed the 468, I installed a Holley 1050 Ultra Dominator. The Mast intake was also designed to run in injected form, so I plugged the injector holes with a set of 19-pound Ford injectors. Equipped with the Mast intake, the power output of the 468 increased to 761 hp and 645 ft-lbs of torque. Not that the peak power rose, but the peak torque dropped compared to the FAST intake. In fact, the long-runner FAST intake offered more power up to 5,900 rpm, but the Mast single-plane pulled away up to 6,700 rpm.
The two-piece Mast LSX intake was designed for high-RPM high-horsepower LS3 applications. (The company also offers cathedral-port and LS7 versions.)
Likely designed for slightly smaller and milder applications, the FAST LSXR intake performed well on this 468-inch stroker. It is hard to argue with more than 730 hp from any manifold.
FAST LSXR vs Mast Carbureted Single-Plane (Horsepower)
FAST LSXR LS3: 732 hp @ 6,400 rpm
Mast Carbureted Single-Plane: 761 hp @ 6,500 rpm
Largest Gain: 47 hp @ 6,700 rpm
The high-RPM nature of the single-plane intake was evident in this curve. The CNC-ported Mast intake was a work of art and boy, did it pull hard on the top end. Unfortunately, all the top-end power came with a trade-off lower in the rev range; in this case, below 5,900 rpm.
FAST LSXR vs Mast Carbureted Single-Plane (Torque)
FAST LSXR LS3: 614 ft-lbs @ 5,100 rpm
Mast Carbureted Single-Plane: 631 ft-lbs @ 5,300 rpm
Largest Gain: 37 ft-lbs @ 4,300 rpm
Much like the previous test run on the Holley Hi-Ram versus the stock LS3 intake, the long-runner FAST LSXR offered considerably more torque up to 5,850 rpm. The FAST offered torque gains as high as 37 ft-lbs lower in the rev range, but the high-RPM single-plane pulled away strong past 5,900 rpm.
Test 3: Stock LS7 vs MSD Atomic for LS7, Modified LS7
This was one of those instances where an intake manifold swap did not trade low-speed torque for top-end power. In fact, this intake improved power through the entire curve, so you know it was the right choice for the engine combination.
Assembled by Cool Performance Machine, the 427 LS7 test engine was created by sleeving an LS3 block. The 4.130-inch bore received a complete Manley stroker assembly that included flat-top pistons, H-beam rods, and a Platinum-series (4.0-inch) stroker crank. Also included in the mix were Total Seal rings, a custom CMP cam (.644 lift and a 246/254-degree duration split), and an adjustable cam sprocket. In true LS7 fashion, the stroker featured an Aviad dry-sump oiling system. Feeding the over-bore LS7 was a set of CNC-ported CMP Brodix SI LS7 heads (395-cfm). Lucas 5W-20 synthetic oil, a Holley Dominator management system and Kooks long-tube headers were included in the mix. The build list also featured an ATI dampener, Meziere electric water pump, and FAST 102-mm throttle body.
It was easy and fast to swap intakes on the LS7. The factory LS7 intake offered good power but nothing compared to the MSD Atomic.
This test involved running the stock LS7 composite intake against the MSD Atomic AirForce LS7 intake, which is also available for cathedral-port heads. Equipped with the stock LS7 intake, the modified LS7 produced 642 hp at 6,800 rpm and 554 ft-lbs of torque at 5,400 rpm. Torque production exceeded 540 ft-lbs for a 1,100-rpm spread (from 4,750 to 5,850 rpm). Since both intakes offered long(ish) runners, I was eager to see how well the MSD compared to the stock LS7.
After installation of the Atomic intake, I was immediately rewarded with both extra torque and horsepower. The peak numbers jumped to 684 hp and 586 ft-lbs of torque. The MSD intake offered nearly 20 ft-lbs below 3,500 rpm but as much as 40 ft-lbs elsewhere. The gains became serious after the tach passed 4,500 rpm. As much as I liked the extra 42 hp (peak-to-peak gain), I also liked the fact that the MSD improved the power output everywhere on this modified LS7.
Equipped with the stock LS7 intake, the CMP-modified LS7 produced 642 hp and 554 ft-lbs of torque. Both intakes were run with a FAST throttle body.
Stock LS7 vs MSD Atomic for LS7, Modified LS7 (Horsepower)
Stock