LS3 In­take Shootout!

We Dyno-Test 19 Man­i­folds So You Don’t Have To

Hot Rod - - Contents - Richard Hold­ener

hWay back in 2015, we per­formed the mother of all LS in­take tests by run­ning 20 dif­fer­ent in­takes de­signed for cathe­dral-port heads. That test in­cluded every cathe­dral-port in­take we could get our hands on, in­clud­ing the var­i­ous fac­tory ver­sions. The prob­lem with do­ing the mother of all in­take tests for the cathe­dral-port guys is that it left out the LS3 own­ers. GM even­tu­ally re­placed the cathe­dral-port heads with high-flow, rec­tan­gu­lar-port heads when it in­tro­duced the LS3, L92, and L76 mo­tors (to name a few). Blessed with what were es­sen­tially race heads right from the fac­tory (flow­ing 315 cfm), the rec-port mo­tors of­fered even more po­ten­tial than the fac­tory cathe­dral-port com­bos. Not sur­pris­ingly, the af­ter­mar­ket jumped on the band­wagon to of­fer all man­ner of in­take com­bi­na­tions for the new cylin­der-head con­fig­u­ra­tion, so it was only nat­u­ral that we had to test them. Un­like the pre­vi­ous ad­ven­ture, we de­cided to split up the EFI and car­bu­reted in­takes and test them sep­a­rately. Pro­vided here for your view­ing plea­sure are the re­sults of part 1 on the EFI in­takes.

Be­fore get­ting to the re­sults, we need to point out a few facts, the first of which is that the fac­tory LS3 in­take is one of the best OE in­takes ever pro­duced. Un­like the pre­vi­ous cathe­dral-port ex­am­ples, even the mighty Trail­blazer SS (TBSS) man­i­fold, the stock LS3 in­take, has proved tough to beat. Oh sure, it’s pos­si­ble to shift power pro­duc­tion higher in the rev range with shorter run­ners, but this usu­ally comes with a trade-off in low-speed torque—some­times a sig­nif­i­cant one. This is an im­por­tant point, as many of these in­takes were not de­signed for our mild cam-only LS3 crate mo­tor—specs on our COMP 54-496-11 hy­draulic roller mea­sure 231/247 de­grees at 0.050 and 0.617/0.624-inch lift with a 113 lobe-sep­a­ra­tion an­gle (LSA)—and would be bet­ter suited to some­thing with wilder cam tim­ing, more dis­place­ment, or both. In­takes should be thought of in terms of en­gine speed (much like a cam). The run­ner length (and other de­sign vari­ables) de­ter­mines the ef­fec­tive op­er­at­ing range. Match this range with the right cam tim­ing, head flow, and dis­place­ment, and you have a win­ning com­bi­na­tion.

The in­ter­net will be quick to grab the peak num­bers from this test and run with them, but there is much more to an in­take, or the power curve it pro­duces, than sim­ple peak val­ues. A re­view of the data will re­veal that the dif­fer­ence be­tween the least and most pow­er­ful in­takes was more than 65 hp. This is a sig­nif­i­cant chunk of change, but peaks only tell part of the story, as ac­cel­er­a­tion is a func­tion of av­er­age power pro­duc­tion. Un­der­stand­ing this, we in­cluded av­er­age power pro­duc­tion from 3,100 to 7,000 rpm. We also in­cluded torque pro­duc­tion at 4,000 rpm, be­cause street driv­ing en­tails much more time in this part of the power curve than at max­i­mum rpm. The point here is that all of the data is im­por­tant, and if you’re look­ing for the very best man­i­fold ever made, you are look­ing in the wrong place. No such an­i­mal ex­ists, so don’t be dis­ap­pointed. If, on the other hand, you’re look­ing for data to select the best in­take for your ap­pli­ca­tion, sit back and en­joy.

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