After a recent discussion with the Editor about the best combination of performance in and dollars out, we decided to go to the source to find out what the GM powertrain engineers would do if they were in our shoes: big power and torque ambitions and a very skinny wallet.
Since 1997, GM has produced the LS1, LS2, LS3, LS4, LS6, LS7, LS9 and LSA engines for Chevrolet and GMC pickup truck, van and SUV applications, SST, Hummer, Cadillac CTS, CTS-V and Escalade, Pontiac GTO and G8, and Corvette applications, and nine different variations in Gen III and Gen IV configurations. This presents the enthusiast builder with a huge array of options and choices using stock factory parts.
We sat down with Dean Guard, chief engineer for all of GM's powertrain small-block engine programs, and his right-hand man, Mark Damico, to talk about what's currently available in the way of LS small-blocks in America's wrecking yards and want ads, which parts go best with other parts, and how to build lots of power, torque and reliability with stock GM parts.
SC: If you were building an LS small-block for street performance use, where would you start?
MD: The '01 and later LQ4 truck engine with aluminum heads gives you 360 hp and six-liters of displacement, with an iron cylinder block. The cylinder heads and the ports are the same as those on the LS6 engine, but the LQ4 has bigger combustion chambers, about 71cc. Stock compression was 9.4:1. If you pick up the LQ9 piston, which is a flat-top piston, you can get back to 10:1 compression. Or, you can just look for an LQ9 engine, which is rare because it was built for the Cadillac Escalade, but we built hundreds of thousands of LQ4 engines for the trucks, so they're easier to find. If you use the piston and rod assembly from the LQ9, which has floating pins, you get the compression, and the 400 hp.
SC: Is there a thinner production head gasket that you could use to get even higher compression without compromise?
MD: We've avoided it because you can get into pushrod problems. We went to a multi-layer steel gasket in 2001. When we set up the engine, we designed it for the graphoil gasket, which was 1.33 millimeters compressed. Multi-later steel gaskets can go down to 0.7 millimeters.
SC: So, you'd recommend the iron-block truck engine for long-term durability?
MD: Unless you really need the lighter weight of the aluminum version to take weight off the nose of the car. The 6.0-liter LS2 and L76 aluminum engine (SSR, Trailblazer, CTS, and Corvette) or the 7-liter aluminum engine is about 100 pounds lighter, but it will be a lot more expensive and harder to find. If you're going to build an engine from the 6.0 or 6.2 truck engine, you should look into the '07-and-later cylinder heads. They have bigger ports, larger valves, and more airflow, and they bolt right on.
SC: Every one of the LS engines since 1999 has come with electronic fuel injection, catalysts, oxygen sensors, black boxes, and so on. Would you recommend buying all of the electronic components along with an engine package, or going to the aftermarket?
DG: You'd have to have the oxygen sensors, for sure, or run an open loop, where the engine will run rich all the time. For most applications, all you really want is the right fuel and the right spark and everything else is not important to what you're doing. There are a lot of decent set-point controllers out there, but the problem is, you have to buy it, and you have to do the work. You have to have the resources to where you can sweep the spark and sweep the fuel and determine how rich you want to be, with how much spark. One of the things you have to watch out for is that we changed from 24X to 58X when we changed from Gen III to Gen IV, which means the crankshaft position sensors used to read 24 times per engine revolution on the earlier engines but Gen IV engines read 58 times per revolution, once every six degrees.