This whole LS engine phenomenon is really rockin', and we wanted to dive right into the party. The difference between Car Craft and the rest of the magazine world is that we're like you-we don't have the $13,000 to drop on a brand-new, all-aluminum crate engine that makes tons of power. Instead, we went the more tradition route of building our own stroker motor.
We were looking for a well-used iron-block 6.0 LS engine, and the national chain of LKQ Auto Parts shipped us a very gritty, complete LQ4 LS engine that fit our requirements perfectly. For those of you not up on LS engine 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 stroker motor. 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.
LS Stroker Motor Machining
We purchased a complete engine from LKQ because we wanted to run the stock heads on our stroker motor just to see how much power we could make. With the benefit of hindsight, we might have saved money buying a long-block. The stock components we reused were the block; the stock front, rear and valley covers; the heads, the valve covers, and the coils. We replaced everything else, including the stock oil pan. Had this been a Camaro motor, we could have possibly reused the oil pan.
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.
Machine Work Description Source Price Clean and Magnaflux JGM $88.00 Bore and torque plate hone JGM $224.00 Deck block JGM $150.00 Balance rotating assembly JGM $198.00 Install cam bearings JGM $44.00Short-Block Assembly
Here's where the fun starts. After returning the block to our shop, we cleaned it one last time with hot soapy water and then began the assembly. We'll spare you the details of the half day we spent measuring bearing clearances. While aluminum block motors need a little more clearance, we aimed for the more traditional 0.0025-inch rod and main bearing clearance spec along with a proper crank endplay and rod side clearance. Assembling the short-block is not much different from building any small- or big-block, but there are some minor details that change. LS engines are actually very easy to assemble.
LS Assembly Tricks
There are some specific differences in assembling a typical LS engine, including a couple of required oil gallery plugs, the front and rear covers need a little attention, and there's a cool technique to installing the oil pump. None of these steps is difficult, and you can bolt on all these parts without expensive specialty tools. Let's get to it.
Final Assembly
Now that the short-block is complete, there are just a few more steps to bringing Lester Scruggs to life. All factory LS engines use torque-to-yield head bolts that can only be used once. Since this engine is destined for multiple cylinder head tests, we opted for a set of ARP heads studs. Another excellent reason to use the studs is to eliminate the problem of blind head boltholes. Coolant or water that seeps into the head boltholes while bolts are installed can cause a hydraulic situation when the head bolts are torqued that can crack aluminum or iron blocks. The ARP head studs eliminate that possibility.
Torque Specs
The following values are a combination of factory and aftermarket fastener torque specs as employed on this engine. The specs for the main and head studs came from ARP and cannot and should not be used with factory fasteners. All ARP torque numbers are with the ARP moly lube. All torque values are in ft-lb unless noted.
*These items were not used in this buildup nor included in the overall price but are included for reference.
**The overall cost of this engine may seem high, but it includes everything from the carburetor to the oil pan, including the starter motor, water pump, belt, and accessory drive. We didn't include the alternator and power steering pump because those pieces were included with the original engine. All these details are items the street engine will need but are rarely included in the overall price of an engine-especially crate engines.
