LS2 Intake Porting - Manifold Destiny

Throttle-body Porting
In addition to porting the LS2 manifold, VMax offers a ported LS2 throttle body that it recommends to enthusiasts who have made additional engine or tuning enhancements. "On stock applications, the ported throttle body will significantly improve low-speed responsiveness, but it really shines when additional modifications-like a free-flowing exhaust and a performance camshaft-are made," says Incaudo. Sold on an exchange basis under PN VMax LS2 TB, the throttle body retails for $150, shipped.

The factory LS2 throttle body bears PN 12570790 and retails for $477.22 directly from GM. Rather than utilizing air tubes to maintain proper idle characteristics, the LS2 unit has an intake-air control (IAC) stepper motor that electronically opens and closes the throttle blades. One shortcoming of this design is the ridge at the leading edge of the throttle blades.

Although it flows more air than both the 75mm LS1 and 78mm LS6 throttle bodies, the LS2 unit can be ported for even greater performance. VMax's changes include boring and blending out the restrictive ridge at the leading edge of the throttle blades, as shown here.

Flow Testing and Forced Induction
Our LS2 intake was flow tested at 28 inches of pressure using a Superflow 600 flow bench. A stock LS2 cylinder head was used initially to document the head flow using only the Number 6 intake port (Test 1). A stock LS2 manifold was installed for Test 2, and flow was again recorded on the Number 6 port with all other runners blocked. For Test 3, a ported LS2 manifold was installed and the test repeated.

Our results indicated that the low- and high-lift cfm numbers benefited the most. Although the cfm increases weren't substantial, intake-manifold porting isn't all about raw numbers. It also has much to do with the transition and quality of air. Pure cfm increases that decrease port velocity or disrupt flow are often counterproductive to hp.

"In forced-induction applications, the ported LS2 manifold consistently outperforms the LS6 and the popular aftermarket intakes during our test sessions," says Incaudo. "When pressurized, any internal leaking is eliminated, and the overall port volume and runner shapes of the LS2 manifold can perform as intended. On a recent session on a chassis dyno, we gained 20 rear-wheel hp-from 695 to 715-by swapping out an LS6 intake on a '03 C5 featuring our CNC-ported LS6 heads and running 15 pounds of boost."

Port and runner stall at 0.550" valve lift.