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FAST LSXr 102mm LS3 Intake Swap

Top Swap: Let your LS3 breathe easier and make more power with an easy LSXr intake manifold upgrade from FAST

Patrick Hill Jan 5, 2016
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Swapping intakes for more power is nothing new in the world of performance. Even with the excellent design of today’s LS-based small-blocks, and all their modern technology, the new top dog in the world of performance still responds to old-school upgrades like this.

Fuel Air Spark Technology (FAST) has recently updated their 102mm LXSr intake manifold, and is also launching a new line of modular intake runners to be used with this two-piece intake, so LS3 owners can use their intake as a tuning tool to better suit racing conditions and other applications. We talked to Billy Godbold at FAST’s parent company, Comp Cams, about the intake’s design and benefits.

“The combination of the enhanced runner geometry over stock for performance applications along with optimizing the plenum volume and allowing a larger throttle body are the main benefits.”

Shortening or lengthening intake runner lengths has long been a way to alter an engine’s performance. In the past, this typically necessitated a full intake manifold swap. But with the new modular runner system, all someone has to do is unbolt the intake, open it up, and swap the runners.

Our test subject Camaro, a 2012 model, already had a full Trick Flow top end kit installed, along with Trick Flow headers and cat-back LSR Performance exhaust system. We were interested to see what an intake swap would do for our car, and after spotting the announcement about the modular runner kits at the 2014 SEMA Show, we definitely wanted to try one out.

At the time of our story, the production runner kits weren’t ready yet, as FAST was still finishing up R&D on them, but the intake itself was ready to go. So, we figured splitting this up into two parts would be best for you, the readers, giving us more space to explain everything. This part will cover the install and testing of the intake as-is, while part two will showcase changing the intake runners, and how shortening or lengthening runners affects engine performance. We’ll also test FAST’s upcoming 102mm drive-by-wire throttle body as well.

We headed to our local LS specialist and dyno shop, Antivenom Performance in Seffner, Florida, to get the job done. We’ll also note that we didn’t do any computer tuning with this intake swap, it was just a straight-up install.

Parts for Fuel Line Assembly
Vendor Part Number Description Price
Summit Racing RUS-640940 Straight Fitting (x2) $10
Summit Racing SUM-220887b 90-degree Fitting (x4) $16
Summit Racing SUM-240820b -8AN Braided Hose 20-feet $1,151
Summit Racing SUM-220687b 90-degree Fitting (x2) $14
Summit Racing SUM-220690b Straight Fitting (x2) $5
Summit Racing RUS-632093 -6AN Braided Hose 20-feet $110
Summit Racing FRA-491989-BL EFI Adapter Fitting $18

1 2012 Chevrolet Camaro 2/33

01. For our baseline, we strapped our test ’12 Camaro SS to the Dynojet chassis dyno at Antivenom Performance in Seffner, Florida. The car put out 433 horsepower at 5,900 rpm, and 408 lb-ft of torque at 5,200 rpm.

2 2012 Chevrolet Camaro Ls3 3/33

02. The LS3 in our ’12 SS already had a Trick Flow Specialties top end kit installed, which consisted of Trick Flow heads, cam, and headers. It also had an LSR Performance cat-back exhaust system.

3 Intake Swap 4/33

03. After letting the engine cool down, we started the intake swap by removing the factory airbox assembly.

4 Factory Ls3 Intake 5/33

04. After disconnecting the fuel line from the fuel rails and removing them, we unbolted the factory LS3 intake and set it aside. The beauty of the LS series is they use a “dry” intake, so you don’t get coolant going everywhere when doing an intake swap.

5 102mm Intake Manifold 6/33

05. The heart of our story is the new LSXr 102mm intake manifold with modular runner capability. Aside from being able to bolt on a larger (102mm) throttle body (especially for engines with power-adders), the enhanced runner geometry over the stock LS3 intake along with optimizing the plenum volume are the LSXr’s main performance benefits.

6 Lsxr Intake 7/33
7 Lsxr Intake 8/33

06-07. The two-piece construction of the LSXr intake opens the door for the interchangeable runner system it employs. This feature allows the hard-core enthusiast and racer to now use the intake manifold as another tuning tool. Being able to lengthen or shorten runner length can change an engine’s performance drastically, allowing for the point of peak power and torque to be moved in the rpm range, along with increasing those peaks to adjust for track and atmospheric conditions.

8 Stock Intake Left Right 102mmintake 9/33
9 Throttle Body Inlet 10/33

08-09. On the left is the stock intake, on the right is the LSXr 102mm. You can see the difference in the throttle body inlet size between the two, which allows for a bigger throttle body and therefore more air to flow into the intake manifold.

10 Vacuum Port 11/33

10. Before installing the intake, you’ll need to cap off this vacuum port on the back, which isn’t need on an LS3 application.

11 Intake Throttle Body Gaskets 12/33
12 Throttle Body Gasket 13/33

11-12. Transfer the intake and throttle body gaskets from the factory intake to the LSXr intake.

13 Greg Lovell Lsxr Intake 14/33

13. Antivenom Performance owner Greg Lovell is always happy to show off his “big guns” and here we could use them to show off the LSXr 102mm’s much larger inlet size.

14 Rubber Isolators 15/33

14. The intake comes with these rubber nubs that must be installed on the bottom of the intake before it is set in place. These rubber isolators help cushion the intake floor against engine vibration, and the vibration caused by the flow of air through the intake.

15 Feed Hose 16/33

15. Before installing the intake on the engine, hook up the feed hose for the power brake booster.

16 Fastening Bolts Removal 17/33

16. To make sure the intake lid doesn’t come loose during engine operation, it’s a good idea to remove all the bolts fastening the lid to the intake manifold base, and apply some thread locker to the threads so they can’t back out from vibration.

17 Front Intake 18/33

17. The map sensor on the 5th-gen uses a larger nipple than earlier LS engines, so the port on the front of the intake must be drilled out to accept it.

18 Holding Slot 19/33

18. With the sensor in place, use the included screw to secure it to the intake via the holding slot, as shown in the photo.

19 Fast Intake Install Kit 20/33

19. The FAST intake install kit comes with button-head bolts that are used to replace the factory valley cover bolts. The factory bolts are too tall and won’t allow you to bolt the new intake down, if you don’t swap them out for the included fasteners.

20 Valley Cover Bolts 21/33

20. With the valley cover bolts replaced, we could set the FAST LSXr intake in place.

21 Stock Throttle Body 22/33

21. Here was an unexpected problem we ran into. With the stock throttle body installed, we had a hair’s clearance between the belt tensioner pulley and the throttle body. While this might not have been a problem, even with the tensioner moving during engine operation, it just didn’t sit well with us.

22 Camaro Tensioner Corvette Tensioner 23/33

22. The solution to our problem was easy though. We swapped out our Camaro tensioner (right) for a Corvette tensioner (left). The Corvette tensioner uses a smaller pulley, along with clocking the pulley at a different spot. The GM part number for this tensioner is 12569301, and is available through Summit Racing, Scoggin-Dickey, or your local Chevrolet dealership.

23 Corvette Tensioner Bolted 24/33

23. With the Corvette tensioner bolted in place (it uses same bolts and mounting location as the Camaro tensioner) we now had plenty of clearance between the pulley and the throttle body. The tensioner swap did require us going to a shorter belt, which we grabbed at the local auto parts store, in our case a Gates K060785. You can use this number to cross reference to whatever brand you prefer.

24 Extender Vacuum Hose 25/33

24. Another item you’ll need is an extender for the 0.50-inch diameter power booster vacuum hose, which is available at most auto parts stores.

25 Factory Fuel Rails 26/33

25. The factory fuel rails won’t work with the LSXr intake so we went with a set of FAST billet rails to complement our install. This also required a little bit of plumbing work on the fuel system. FAST sells a fuel line conversion kit (PN 54028-KIT) that is designed for 4th-gen Camaros but can be adapted with a few tweaks to work on a 5th-gen.

26 Custom Fuel Line 27/33

26. We wanted a certain look with our install though, so we decided to ring up Summit Racing and order the individual parts to make up our own set of custom fuel lines. The part numbers for everything we ordered can be found in the sidebar elsewhere in this article.

27 High Pressure Rubber Line 28/33

27. From the high pressure rubber line, you’ll need two pieces, one piece cut long enough to join the two fuel rails, the other to run from the passenger side fuel rail to the main fuel line coming off the body. To install the AN fittings on the rubber line, unscrew the end from the fitting, then insert onto the rubber line as seen here.

28 Screw Fitting 29/33

28. Then screw the fitting into the receiver as such.

29 Fuel Rail 30/33

29. This is what you should have, ready to be connected to the fuel rail.

Fittings 31/33

30. These fittings are used to connect the line coming off the rail to the body fuel line, while retaining the quick-disconnect feature of the original fuel lines.

30 Lsxr Intake Factory Engine Cover 32/33

31. And here’s how it all looks when done. The factory engine cover can’t be installed with the LSXr intake, which isn’t a loss in our opinion. Seeing that FAST intake instead is much better.

31 Dyno Results 2012 Camaro 33/33

32. On the dyno, we saw a big increase with the new intake, far exceeding our expectations. The LS3 cranked out 469 horsepower at 6,200 rpm, and 448 lb-ft of torque at 5,100 rpm. That’s a gain of 36 horsepower and 40 lb-ft of torque over our baseline. The other bonus was we didn’t lose any power down low, and saw increases in torque and horsepower throughout the rpm range, especially in the upper powerband.

Dyno Numbers
RPM LS3 Intake LSXr 120mm Intake
HP Torque HP Torque
3,100 210 355 216 366
3,200 220 361 229 376
3,300 231 368 239 381
3,400 242 374 256 395
3,500 251 377 271 406
3,600 262 382 284 414
3,700 273 388 292 415
3,800 282 390 301 417
3,900 289 389 313 422
4,000 295 387 320 420
4,100 307 393 336 430
4,200 316 395 348 435
4,300 326 398 360 440
4,400 335 400 367 438
4,500 340 397 373 435
4,600 350 400 384 438
4,700 356 398 390 436
4,800 365 399 400 438
4,900 373 400 408 438
5,000 382 401 422 444
5,100 396 408 433 448
5,200 405 408 439 444
5,300 412 406 445 441
5,400 412 401 449 437
5,500 415 396 450 429
5,600 418 392 454 426
5,700 419 386 452 416
5,800 421 382 453 411
5,900 433 386 452 403
6,000 432 378 459 402
6,100 429 368 463 399
6,200 428 363 469 394
6,300 422 363 464 387
6,400 420 352 462 379
6,500 419 352 460 372


Summit Racing
Akron, OH
Seffner, FL 33584
Memphis, TN 38118



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