Speed Secrets: 408 Fast Intake Test

What’s the difference between the FAST LSXR and single plane intake? Richard Holdener explains in this episode of Speed Secrets. 

Single plane carbureted intakes are notorious for making big peak power, and the Fast LSXR intake is the best of the best when it comes to LS EFI applications, but how do the two compare? To find out, on an episode of Speed Secrets Richard Holdener and the guys from Fast stage an intake shoot out.

For a test engine, Richard picked up a 408 LS stroker short block from ATK and topped it with a set of factory GM LS3 heads. A healthy camshaft, 54-470-11, from Comp Cams was installed along with dual valve springs, hardened pushrods, Max Lift Shaft Rockers, and Fast Ignition Coils. With a single plane intake and an 850 carburetor the LS Stroker made 554 HP and 519 Lb-Ft of torque, which is not bad at all. 

Removing the trusty single plane intake, the guys then installed the Fast 102mm LSXR intake with a matching big mouth throttle body and 89 Lb injectors. Judging solely on peak horsepower it looks like the single plane Intake has a 2 HP advantage where as the Fast intake took a 10 Lb-Ft lead in torque, but peak numbers don’t tell the whole story. 

In looking at the graph of the entire power band its clear that the Fast LSXR is the winner. From 3,500-6,000 RPMs, the long runner Fast intake made more power and torque than the single plane manifold. The gains, as much as 27 Lb-Ft at 4,200 RPM, offered a solid 12-15 Lb-Ft improvement throughout the entire power curve. In fact, it wasn’t until above 6,000 RPM that the single plane started to make a little more power, proving the Fast LSXR intake manifold is tough to beat.