It’s now been over a decade since General Motors released its fifth-generation small-block V8, coded LT. Launched in 2013 with the C7 Corvette, the LT ushered in a new era of pushrod performance thanks to the addition of direct injection. It also represented the company’s first wholesale redesign of its small-block architecture since the 2005 Gen IV, which itself was heavily based on 1997’s Gen III platform that introduced the now-legendary LS series to the world.

First published in the November 2024 issue of Street Machine

Although the Gen V LT may appear outwardly similar to those Gen III/IV LS mills, only the 4.40in bore spacing, deck height, 90-degree V, cam location and pushrods are shared. To suit direct injection and new packaging methods in modern cars, the block and mounting bosses were redesigned, and this is an important consideration if you’re looking to swap an LT into a classic car.

Fortunately, one of Australia’s foremost experts on engine and chassis swaps, Jason Waye of Tuff Mounts, recently slung an LT V8 into his HQ Kingswood wagon, and he’s applied what he learned during the process to create a Tuff Mounts LT swap kit, which should be available to purchase by the time you read this. We asked him for the full lowdown on what was involved.

SWAP SHOP

If you’ve read this far and found yourself dreaming about chucking one of GM’s new, 1064hp, twin-turbo LT7 V8s (Tech Torque, SM, Sep ’24) into your HQ-WB, we have some bad news. The 5.5L, DOHC LT6 and LT7 mills are part of GM’s Gemini Program, which shares no DNA with the production LT engines, so the Tuff Mounts LT kit won’t work for them.

The good news is that the iron-block 6.6L L8T truck engine does share family architecture with the LT, so Jason is already looking at cooking up a seriously spicy L8T project in the future. “Commodore LT kits will be what we bring out next, and then I think we should have a look at the L8T and see how far we can go with that platform,” he says

TOTAL CONTROL

Rebuilt and toughened up by Steve at Shift Right Transmissions, GM’s beefy 4L80E overdrive transmission shifts gears in Jason’s Quey. But how is he planning on running the electronically controlled auto?

“I’ve been mucking around with a prototype version of Haltech’s new Ti4L transmission controller,” Jason explains. “It plugs into the ECU and has been super easy to set up and configure.”

The Haltech Ti4L looks to be a great solution for those wanting to run a modern, electronically controlled GM 4L-series trans in their street machine, and we’ll bring you more info upon its public release.

Step-by-step

1. Jason sourced a low-mileage, second-hand L87 – a truck variant of the 6.2L LT1 found in Corvettes and Camaros – and had it freshened up by Cory Read at Read’s Mechanical. Apart from the intake manifold and a few minor differences, both the L87 and LT1 share very similar specs.

2. The amount of tech in the Gen V small-block provided Jason with plenty of challenges, starting with the direct injection (DI) system. “I thought this engine swap would be super easy, and we even changed our engine to port injection to simplify it, but there’s nothing the same as on an LS,” he laughs.

3. Jason fitted a Brian Tooley Racing intake manifold to switch the L87 to port injection. “There aren’t many aftermarket computers that can run the direct injection system, and we’re all used to port injection with the LS, so the theory with converting our engine to port injection was that it would be just like an LS3,” he says.

4. It isn’t just the direct injection that’s tricky with LTs. “There is also the variable-pressure oil pump and variable valve timing,” Jason explains. “We didn’t need any of that, as that’s all for economy and emissions to try to make these pushrod engines as clean as possible.”

5. Jason sourced block-off plates for the DI injectors from ICT Billet, along with the alloy valley plate, but he will have Tuff Mounts equivalents on the market by the time you’re reading this. “There are a couple of different-diameter injectors used in LT,” he says. “Early ones are 6mm; later on, they’re slightly larger.”

6. Jase tried something new with this project: 3D-scanning. “We 3D-scanned our engine before we started making parts, and this helped us massively when it came to prototyping designs,” he explains. “We then 3D-printed prototypes to make sure they fitted how we wanted, and were then able to put them into production with no rushing or hurrying anyone along.”

7. The HQ runs this aftermarket cast-alloy sump thanks to another curveball the LT lobbed Jason’s way. “On all the LT sumps, there is an integrated oil pick-up, which makes it pretty damn annoying to get around,” he says. The sump you see here will be available for purchase from Tuff Mounts.

8. The Tuff Mounts LT features a VE Commodore water pump, both for practical and aesthetic reasons. “If you look at a Gen V water pump, they’re bloody ugly, and they make it difficult to run drive accessories on the front,” Jase says. “I also struggled to find water pumps in Australia for them. We were playing around with the scan data and made the adapters to convert the VE pump to suit the Gen V engine.”

9. Chasing reliability at a reasonable price, Jason chose this VE Commodore radiator and fan package for the HQ. “We ran a VE V6 radiator in the Fox-body (SM, Aug ’22) and never had any problems,” he says. “The hope is to use factory radiator hoses, even if they require a little trimming.”

10. The Tuff Mounts crew used their 3D scans to design adapters that match the Gen V water pump inlet and outlet with those of a VE Commodore, while maintaining the correct accessory belt offset. The Commodore parts should also be easier to source locally than Corvette or Camaro spares.

11. GM moved the engine mounting bosses on the Gen V, so Jason made all-new mounts to suit.

12. Behind the factory timing cover is an American-made Katech billet oil pump, chosen so that Jason didn’t have to deal with the complexity of controlling the LT’s factory variable-pressure pump.

13. A BTR 225 bumpstick is hiding behind this new Tuff Mounts VVTi-delete cam plate. While variable valve timing can improve the spread of power, it’s not super-beneficial in a typical street machine application. The plug on the front of the cover is for the Gen V cam position sensor.

14. The BTR Trinity port-injection manifold is a popular option for people pushing serious power through Gen V mills. General Motors itself ran a port-injection manifold on top of the direct-injection system on the 755hp, supercharged LT5 V8 used in the C7 Corvette ZR1.

15. One thing that did make the swap easier was the LT’s physical size being very similar to the old LS. With the same deck height and bore spacing, a Gen V should fit anywhere a Gen III or IV can, albeit with new mounts.

16. One thing that did make the swap easier was the LT’s physical size being very similar to the old LS. With the same deck height and bore spacing, a Gen V should fit anywhere a Gen III or IV can, albeit with new mounts.

17. “In America, the LT platform has been going for years, but there is nothing out here,” Jason says. “The swap wasn’t difficult to do, but it took heaps of time and reading to understand how to make it work. Bill at RaceMAX Direct provided a lot of advice, and having a direct line to the guys at BTR through him was key.”

18. While a factory drive-by-wire throttle would have worked, Jason’s pursuit of simplicity saw him opt for an old-school cable throttle. “This means we don’t have to hang a new accelerator pedal,” he says. “I had the 102mm Nick Williams throttle on the shelf, so it worked out perfectly.”

19. Switching to port EFI and removing some of the tech from the Gen V has made controlling the 6.2L mill a breeze. “We talked to the Haltech team and ran through our idea, and after a few brainstorming sessions, we worked out that their Rebel LS should run this combo no worries,” Jason says.

20. “We received a lot of help from companies like Haltech and RaceMAX, even though we had some weird requests for them,” Jason says. “The LT platform is largely unknown down here, but these companies were so eager to help us out and really made it possible.”

21. For wiring, simplicity once again ruled the day. “The stock cam sensor and VVTi sensor are still there, just unplugged,” Jason says. “We need to change the cam sensor plug on the Haltech loom, but everything else is just like a Gen III/IV, and we are using mostly factory parts.”

22. “We don’t have plans to go crazy with the power, as the HQ is just a street car; I don’t want to put a ’cage in it,” Jason says. “Our LT kits will be available by the time of Drag Challenge 2024; we’re waiting for confirmation on one final part before we’re good to go.”

23. “Access to the LT engines is far greater in America, as they’ve been on sale there for so long,” says Jason. “LS V8s are getting more difficult to find, as they’re so old now; the LS was introduced in 1997! This HQ hasn’t been a cheap build, but I think we can make it a lot cheaper and easier for everyone else.”

24. A TCE flexplate and converter join the LT to a 4L80E four-speed auto, which was freshened up by Steve at Shift Right in Sydney. The LT retains the same standard bellhousing pattern employed by Chevy small-blocks right back to the 60s, allowing for a range of transmission options.

25. A new transmission crossmember and rear mount have been designed for the Tuff Mounts LT swap kit. The crossmember includes pass-throughs for dual exhausts and was designed to work with a range of transmissions. Jason found he only had to do a little massaging of the HQ floor to fit the big 4L80E, despite it being noticeably fatter than a TH400.

26. The standard alternator placement on Gen V engines wasn’t going to work in the HQ due to the front-mounted steering box. Tuff Mounts has designed a low-mount alternator bracket for the RHD market, which Jase says should suit most popular Holdens.

27. Aussie street machiners have been hesitant to embrace the LT platform, thanks largely to the complexities around the direct injection, drive system, and the variable timing and oil pumps – not to mention the fact that LS-specific mounts and headers won’t work. But in tackling Jason’s HQ project, he and the Tuff Mounts crew worked out solutions to these issues so you wouldn’t have to! The resulting Tuff Mounts swap kit makes the LT a bolt-in proposition for popular platforms like HQ-WB using off-the-shelf parts. Now, get swappin’!