Inside an LQ4
The engine we chose to work with is the all-iron 6.0L Gen III small-block that appears in many different larger pickups and SUVs. Despite the fact that this is a truck engine, it offers more power potential than a typical LS1 5.7L engine because of its greater displacement and larger, 4.00-inch bore. The iron blocks are otherwise identical to their aluminum counterparts, are notably stronger, and add only 65 pounds. The stock LQ4 engines also use a lower 9.4:1 compression ratio compared with the 10.2:1 compression ratios offered in the LS1 engines. More rare but also out there is the Escalade LQ9 with more compression and more power. Other major differences in this LQ4 engine are the use of the taller EFI intake manifold, a deeper-sump oil pan, truck exhaust manifolds, and the truck-specific accessory drive. Because our first few tests were intended to be used with a carburetor on the engine dyno, the EFI manifold was not included. Even though the truck oil pan will not fit a Camaro or Chevelle engine swap, we left it in place for the dyno testing. The truck accessory drive was also not a problem to retain, but we had access to an F-car-style (Camaro/Firebird) front accessory drive, so that's what we used instead of the LQ4 version. Finally, we added a set of Kooks Gen III headers instead of the stock exhaust manifolds because we were assuming that most enthusiasts would run this engine with headers in an older musclecar.
One of the nice things about this new generation of engines is that they are extremely easy to work on. If you are planning on reusing the EFI manifold, it does not require gaskets, as the intake employs a reusable rubber O-ring seal around each intake port. In our case, we intended to use a carburetor, so we lifted the EFI manifold and installed the GM Performance Parts aluminum carbureted intake manifold. This manifold requires the usual gaskets, which Fel-Pro offers. On top of the manifold, we used our battle-tested-tough, Holley mechanical-secondary, 750-cfm 0-4779 carburetor.
Because the LQ4 6.0L is part of the Gen III family, it also uses the GM coil-near-plug distributorless ignition system. The quickest and easiest way to get a carbureted engine running is with MSD's timing/rev control box. MSD has come up with a small electronic box that "talks" to the GM smart coils and triggers them with the appropriate spark timing. The MSD can be fine-tuned for initial timing, as well as both "mechanical" and "vacuum" advance curves by making changes to a couple of very easy-to-understand timing graphs on a laptop computer. That sounds complex, but even we managed to figure it out within about 20 minutes and soon had our initial timing and a full advance curve dialed in.
We configured the engine this way to avoid dealing with the perception that this conversion is overly complex and expensive. The negative side to this plan was that the GMPP intake and MSD electronic conversion box were not cheap, adding more than $850 to the cost of our 6.0L engine. If you chose to retain the factory intake manifold, you could modify the factory electronic fuel and spark curves by using aftermarket tuning software, such as HP Tuner or LS1 Edit to achieve similar power levels. You wouldn't even have to change intake manifolds, since our experience is that the factory truck intake is especially good at making torque while sacrificing only a reasonable amount of peak horsepower. We decided to stick with a carburetor for this series of testing owing to its simplicity.
We also bolted on this GM Performance Parts carbureted aluminum intake manifold along with
We used a set of 131/44-inch Kooks headers on the dyno plumbed into a pair of 211/42-inch
Cam swaps are easy with the Gen III engines. Begin by pulling the rocker shafts off the he
When installing the new cam, sometimes the rear cam sensor has to be lifted slightly out o