Is the extra 20 or so horsepower worth the cost of the FAST manifold? That is something every 5.3L owner will have to decide, but remember, these gains will only increase with wilder and/or larger LS combinations. The power was up nearly everywhere with the LSXRT, to say nothing of nearly reaching the 500hp mark, but the question remains. As expected, the big winner in our truck trio was the FAST LSXRT intake and FAST 102mm throttle body, which produced 492 hp at 7,100 rpm and 422 lb-ft at 5,800 rpm. The TBSS intake improved the power output from 4,500-7,000 rpm. Equipped with the TBSS intake, the power numbers increased to 473 hp at 6,800 rpm and 419 lb-ft at 5,300 rpm. Next up, we installed the TBSS intake and 90mm Holley throttle body (the throttle opening on the SS intake was larger). After dialing in the air/fuel ratio and timing, the 5.3L produced peak numbers of 464 hp at 6,900 rpm and 414 lb-ft of torque at 5,300 rpm with the stock truck intake. To start the test, we installed the early truck intake and Accufab throttle body. The LM7 was run sans accessories and with a manual throttle body swapped in place of the drive-by-wire unit. Save for new Fel-Pro MLS head gaskets and ARP head studs, the remainder of the LM7 short block was left stock.įor testing, the 5.3L was equipped with Hooker 1 7/8-inch long-tube headers, FAST 46-pound injectors, and a Holley HP EFI management system. The spring package supplied on the GenX 205 heads was more than adequate for the hydraulic roller cam lift and rpm potential. The GenX 205 heads were combined with a healthy Comp cam (Grind # 277LrR HR13) that featured a 0.614/0.624-inch lift split, a 227/243-degree duration split, and 113-degree LSA. The GenX 205 heads were designed specifically for the small-bore LS applications (4.8L-5.7L), and offered enough flow to support well north of 550 hp on the right application. The stock 706 heads were swapped out in favor of a set of Trick Flow Specialties (TFS) GenX 205 heads. Rather than run them on a stock LM7, we upgraded our high-mileage, junkyard engine with ported heads and a cam. The best compromise was to test them on what the majority of enthusiasts are running, so naturally we turned to the 5.3L. Compared on a bone-stock engine, the gains offered by the TBSS and LSXRT would be greatly minimized, but running them on an 800hp, big-inch stroker would be equally foolish. With the original truck intake being so versatile, is it possible to better the factory truck intake? That's what we are here to find out.Ĭhoosing the test engine was as important as the intakes we planned to run. As luck would have it, the factory truck intake is a solid performer, bettering both the original LS1 and LS2 for power and nearly matching the much-sought-after LS6. See part 12660709 for matching fuel rails. Intake 12580420 has a PCV port and is configured for the 1999-2006 style MAP sensors. Excellent upgrade for 1999-2006 4.8, 5.3 and 6.0 LS Truck Engines. Highest Performing factory Cathedral Port Intake. What this means is that there are also thousands upon thousands of truck intake manifolds available. Genuine GM 12580420 TBSS Intake Manifold. As if that weren't enough, the smaller 4.8L and larger 6.0L both shared intake manifolds with the 5.3L. GM produced literally millions of trucks and in many cases the 5.3L was the base engine, meaning it was produced in the greatest numbers. The reason behind the popularity is that they are both powerful and plentiful, always a good combination. The 5.3L has quickly become the go-to engine for swaps, performance builds or just about any type of performance use. sporting higher compression and 243 heads, everyone loves 5.3L truck engines. leaves the intake clean looking.It doesn't matter whether it's a lowly LM7 or a top-of-the-line H.O. Looks wise anything is better then a TBSS it looks like dog shit, especially with all the wires running over the top.Īlso if you swap to LS2 you will need new fuel rails, and if you don't clean up and modify the engine harness it will cross over the top and defeat the purpose (looks wise) I can clean up the harness for you, or you can do it your self. Your only choice is a LS2, you can get it ported or get a Ls6 with a LS2 plastic nose plastic welded onto it.Īnything other then the factory 5.3 (TBSS) is going to be a downgrade performance wise. LS6 flows the best, but is limited to a 3 bolt 8 wire throttle body, which isn't really compatible with your truck 4 bolt 6 wire throttle body. LS3,L92 won't work either they are rectangular ports. LS7, has its own heads, won't work on any other motor, unless you swap heads, but then you need a larger bore to accommodate the larger valves. I take it you want to swap the intake onto your Blue V8 rado? They are basically a aluminum Gen IV version of the LM7 cast iron block 5.3L, they have cathedral port heads like the LS1,Ls2,LS6 truck motors (except L92).
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