GM LS Engine Build - Lester Scruggs

We were looking for a well-used iron-block 6.0L motor, and the national chain of LKQ Auto Parts shipped us a very gritty, complete LQ4 engine that fit our requirements perfectly. For those of you not up on LS architecture, the iron 6.0L is the least expensive route to the most displacement. These iron-block 364ci engines sport a stock 4.00-inch bore and a 3.62-inch stroke. In the May '07 issue ("550 HP for Under $4,900"), we bolted a set of untouched L92 heads on a stock LQ4 short-block and with a mild Comp cam made a carbureted 550-plus horsepower. That got us thinking that if we punched up the displacement with a stroker crank, we could make even more torque and horsepower. That's what our Lester Scruggs (his initials are LS) motor is all about. To pump him up, we added a Scat 4.00-inch forged-steel stroker crank, a set of Mahle pistons, and other goodies.

This month, we'll detail the assembly techniques along with a couple of simple, inexpensive tools you'll need to assemble an LS engine. You may have heard about expensive assembly tools required to build these engines. This seems to come from people who have never built one. The truth is, you don't need those pricey tools, and the ones you do need can either be built for free or are reasonably priced. The only other specific tools you'll need are a handful of metric sockets and end wrenches-that's it. So follow along as we rub a little personality into Lester Scruggs.

Jim Grubbs Motorsports did all the precision machine work, which included a sonic cleaning, boring and torque-plate-honing the cylinders, and then a careful decking. Here's where we missed a chance to bump the compression more by placing the pistons at just below deck height like we've done with all our previous small- and big-blocks. The difference is that all LS engines use multilayer steel (MLS) head gaskets that generally measure around 0.050 inch thick. This creates a less-than-optimal piston-to-head quench area of more than 0.055 inch. We should have decked the block to push the pistons out of the deck by perhaps as much as 0.010 inch. One way to help this is to use thinner MLS gaskets, now available through Fel-Pro. With the 12cc dished Mahle pistons, a -0.005-inch deck height, a 0.053-inch head gasket thickness, and a 70cc combustion chamber, the static compression computes out to 9.8:1. The reason for the slightly dished pistons is because we plan to give Lester an ego boost with a blower in the near future and the conservative compression makes it easier to crank up the manifold pressure on pump gas. Mahle makes a flat-top piston in this bore/stroke application that bumps the compression to 11.1:1.