Are Carbs Still King?
Part 2: LS3 Intake Insanity
In the July 2018 issue of HOT ROD, we hatched a plan to test every intake manifold for the LS3 engine that we could get our hands on. Given the popularity of the rectangular-port LS3 configuration, it was only natural that the aftermarket embraced it with open arms and offers all manner of intake manifolds, both carbureted and fuel injected. In fact, there were so many intakes available for the LS3, we had to break our test into two parts. Part 1 covered the EFI intakes; in this installment, part 2, we tested a variety of different carbureted intakes. After all, man does not live by EFI alone, and carbs are plenty popular for many performance applications. Thanks to performance products like the MSD ignition controller, adding a carbureted intake to your LS3 has never been easier. But which one do you choose?
Much like our test on the EFI intake shootout, we need to point out a few facts before we get to the results. For this test, we compared all of the intakes to the factory LS3 EFI intake. The combination of average and peak power makes the stock manifold difficult to beat. If you don’t believe us, just check out the results of part 1. Knowing that an intake should be chosen for the intended combination, and no test engine will offer the right combination for all intakes, we decided to throw in a twist for part 2. Rather than use the cammed LS3 crate engine in part 1, we stepped up and built a 415 stroker using components from Wiseco, K1, and AFR. Using an LS3 block from Gandrud Chevrolet, we assembled a powerful combination that we hoped would better favor the power potential of some of the single-plane intakes from Edelbrock, Mast, and TFS. Of course, this wilder combination was less well suited to the dual-plane intakes, but such was the trade-off inherent in testing them all on one engine.
The various LS groups might gravitate toward the big peak numbers, but as always, there is much more to any given combination than simple peak power and torque. A comparison between the least powerful dual plane and the most powerful single plane revealed a difference of 54 hp, but that hardly tells the whole story of the comparison between these two extremes. Though the single plane offered as much as 63 hp at 7,000 rpm over the dual plane, the dual plane offered an additional 62 lb-ft of torque at 3,500 rpm. For any kind of acceleration contest, the single plane would be the clear winner, but not every LS3 owner is looking for low elapsed times and high trap speeds. The dual plane even offered more low-speed torque than the factory (long-runner) LS3 intake, which is no easy feat!
Knowing there are endless reasons behind choosing an intake, we included not only peak power numbers but also things like average power production from 3,500 rpm to 7,000 rpm, as well as torque production at 4,000 rpm. As indicated in part 1, if you are looking for the most powerful manifold ever made, you are looking in the wrong place. It simply doesn’t exist. However, the information provided here should help you choose one to suit your carbureted application. Be sure to check out our video to hear them run!