Seeing the light at the end of the tunnel is one of the best parts of any build. Knowing you’re close to finishing a significant upgrade or restoration can be insanely gratifying and we are happy to bring your some closure to our LS3 engine install! A few issues back, we began our prep work on this part of our project, and if you’ll remember we figured out the height for the custom motor mounts, solved our pulley situation, changed out the factory oil pan to replace it with a Holley aftermarket model, and installed a Be Cool radiator to keep the engine running cool. In this issue, we pull out the engine one last time in order to marry it to the 4L80E Gearstar Performance transmission. While the engine was pulled out, we took advantage of the situation and shaved the firewall to clean up the engine compartment, allowing us to do the final mock up.

As this project came together we reached our goal of streamlining the engine compartment and modernizing our performance with one of GM Performance’s bestselling crate engines. The new crate engine was reassembled to the car in a few hours, and we jumped right in doing the final step that everybody usually hates; the rewiring. Thanks to some detailed instructions and user-friendly technology from GM, we were able to wrap the wiring process in just under 2 hours! This part of a build is usually tedious and extremely frustrating, so we must acknowledge GM’s efforts in creating a much more efficient and easier to install product. They really outdid themselves with this LS3. Now follow along, as we wrap up the install of this 6.2 liter GM Performance crate motor.

1. In the last installment, we left off with the engine fitted in place but we decided that we had to add a few cosmetic improvements; therefore we needed to pull out the engine one last time.

2. We had initially used a mock-up transmission before installing this Gearstar Performance 4L80E transmission, which was pretty much a plug-and-play system.

3. Before installing the transmission, we had to install the Flexplate or “Flywheel” as some of us refers to it. The Flexplate size will be dictated by the transmission that you use, in our case, a 4L80E.

4. We found our Flexplate at our local Auto Zone and matched it to a 2004 Trailblazer, which is what this transmission was originally used for. Coincidentally, this flywheel is the same as those found on a Suburban, Tahoe or 1500 truck.

5. To make sure that the Gearstar transmission was secured, we held it in place with a new CPP cross member, designed to bolt up from the stock location.

6. We upgraded the stock transmission mount with an Energy Suspension mount that will be able to hold up to the torque.

7. Jason married the engine and transmission together in order to slip the engine back in place.

8. To check the fluids, we used a Lokar transmission mount dipstick.

9. We were ready to install the engine and transmission combination.

10. The CPP cross member attached easily and flawlessly as it bolted up to the old factory specs.

11. Our next item on the agenda was to find a set of exhaust manifolds that would work in this application.

12. As you can see it was a tight fit, but these headers attached with no major problems.

13. For exhaust part of the build, we used Pypes stainless exhaust system.

14. The pre-bent exhaust attached and will flow smoothly as it was mandrel-bent for a better flow.

15. The throttle body was ready to plug in, but not before modifying the factory fuel rails.

16. The fuel rail was removed in order to modify it for a fuel line input.

18. We visited Alternative Hose in Anaheim, CA and Hector suggested this weld-on #6 AN fitting.

19. After a quick weld, the fuel rail and injectors were reattached.

20. As you can see, the fuel input will be easier with that #6 male fitting ready to accept the fuel line.

21. Wes helped out by laying out the harness.

22. This engine harness was easy to hide and really cleaned up the look of the engine. In the future, if we want to add the coil pack covers, all of the wiring will appear to be stealth and very clean.

23. We decided to keep the ECU, or computer, safe from the elements, so we had to cut out the firewall to allow the bulkhead on the harness to slip through.

24. The factory access panel was bolted back on and covered the hole, keeping the elements down to a minimum.

25. Here is a closer look at the harness and the engine computer before it was put inside the interior.

26. It was time to clip the harness to the computer.

27. With the computer plugged in, we just had to bolt on the drive-by wire gas pedal.

28. For an air intake, we used Spectre’s air cleaner.

29. We mocked up the air cleaner to figure out what other parts we needed from Spectre Performance.

30. The results came in the form of this 90-degree 4-inch tube that will also hold the mass airflow sensor.

31. Last order on the wiring menu was this power fuse block. This fuse block distributes power to the engine coil and accessories.

32. As you can see, the fuse box is protected for the elements with a cover. We are going to bolt this fuse box on the fender wells once the fenders are back on.

33. This engine was all wired, plumbed, and ready to be fired up!