If you've been following the buildup of GMHTP's project 2001 Trans Am WS6, you know that we've been hinting at an imminent displacement increase. While bolt-ons like our full exhaust, big intake, and direct-port nitrous system have gotten excellent power increases out of this Pontiac's internally stock engine, there's nothing like a bump in cubic inches to really wake things up.
Unfortunately, pumping up cubes usually means pumping many thousands of dollars in the direction of a speed shop's bank account. Highly competent shops exist throughout North America that will be happy to take your hard-earned cash and turn your late-model, Gen III-powered ride into an impressive performer. This is definitely not a bad way to go.
But putting together one's own high-power, stroked EFI engine can be just as--or more--rewarding than enjoying the end product. After all, anybody with a wad of cash and zero hands-on knowledge can drop his or her car off at one of the aforementioned establishments and drive away a few weeks later with a couple hundred extra horses under the hood. The more unique breed of person dreams of building and installing such an engine at home, thereby gaining the satisfaction of tackling a seemingly daunting task many would not dare. But can such an undertaking really be done in the average suburban garage? Or is this power-hungry do-it-yourselfer destined to spend thousands of dollars extra having a shop build and install this stroked motor instead?
The time has come to find out. We're going to double the fun and halve the cash by building a stroker in our own garage. Follow along as we transform our Trans Am's 346-inch LS1 into a 383-cube LS-wonder.
STROKER PARTS SELECTION
As we've hopefully made clear, there are two interlocking themes to this story: build-it-yourself, and build on a budget. The two go hand-in-hand, as the do-it-yourselfer is likely building his or her own engine in large part to save labor costs.
The question of what one looks for when building a budget-conscious stroked LS1 can't be asked unless one knows how tight cash really is. Someone on an absolute shoestring budget can get away with cost-saving measures like reusing the stock cylinder heads and just having a simple port job done to them. However, when it comes to the parts to actually make the engine a stroker, there are minimums of what must be bought, and the major items include a crankshaft, connecting rods, and pistons.
Before we get into how to go about choosing components, keep in mind the single most important canons of engine building: inform yourself, set realistic goals, and stick with your decisions throughout the stages of selecting parts, engine assembly, and eventual enjoyment out on the road. Ignore these, and disaster is certain to occur. And while we'll guide you in the right direction of understanding stroker LS1 component design and selection, we'd be doing you a disservice if we purported to include "everything you need to know." We just don't have the room to cram it all in. So, do your research! We'll mention some good books to pick up, and of course there's a ton of info to be garnered from visiting LS1-oriented Web sites. It also helps to make sure you pick up a copy of GMHTP every month!
Crankshaft: The Heart of a Stroker
GM uses a 3.622-inch crankshaft from the factory in the LS1; so how much bigger should you go? For our application, we wanted to make sure we would still have a reliable, daily drivable car that wouldn't suck fossil fuel like there was no tomorrow. Therefore, we chose to go with a 4-inch stroke, giving us 383 cubic inches (6.3 liters). Though larger cranks can fit, our choice to forego "throwing in the kitchen sink" is based on a few things in addition to those we've already mentioned. First, clearancing of the block will be minimal, saving us headache. And, keeping our planned moderate nitrous usage in mind, we'll limit our horsepower level enough that we'll be able to safely stick with our stock steel main caps without worry that we should have shelled out cash for some expensive billet units--and the accompanying machining costs to fit them to the block.
The analysis doesn't end there. Absent an adjustment in rod length, increased crankshaft stroke will decrease compression height (the distance between the centerline of the piston pin and the face of the piston). With our plans for nitrous use, we wanted as much ring land strength as possible; the smaller the compression height, the less space there is for the rings, and at a certain point the top compression ring will have to be moved too far toward the face of the piston, exposing it and the now-thin ring land to more heat than they can bear. You'll see these dimensions explained further in the photo captions when we get to piston assembly.
Connecting Rods and Pistons: Adding to the Equation
There are a lot of LS1 stroker crank manufacturers, and that variety extends to the rods and pistons. When choosing each of these components, the money you'll need to spend will rise with the amount of horsepower you're looking to make. It's possible to go overboard for a budget street build--but more importantly, it's possible to "cheap out" and buy parts from less reputable companies, many of whom have their stuff made overseas. It is far better to spend a little extra money on a company with a good name, so you can rest easy knowing the parts will stand the test of your lead-weighted right foot.
Matching all of these items can be a hassle though. Different crankshafts are often manufactured with varying journal shapes as well as counterweight sizes, so this limits the range of rods that can be used. (We are not going to get into the debate on optimum rod length here; it's beyond the scope of this article. You've probably heard it: longer rods decrease piston side loads, while shorter rods increase piston speed and decrease dwell time.) Different piston designs can interfere with the shape of the crank throws at bottom dead center, and different rod designs and lengths also affect piston specifications. Plus, after juggling rod length with piston pin height, you have to throw all of this into your compression ratio equation.
Worst of all, after the hours upon hours of head-scratching and parts-matching, the crank must be precisely matched to the rods, pistons, and all other reciprocating masses using a process called "balancing." This can get expensive; it involves drilling and often adding heavy, pricey Mallory metal in precise locations in the crank counterweights. Think of it like balancing a wheel and tire--only it's much more complex, and the stakes are far higher.
Save yourself the headache of all of the above issues and buy an entire rotating assembly that is already matched, balanced, and ready to go. It takes a lot of potential for error out of the equation--and you'll save money, too, as it's a package deal. Rotating assemblies for high-power, reasonable-budget builds like ours are readily available in many different configurations of stroke and piston type; see the sidebar on the Lunati rotating assembly we chose for this build.
The Rest of the Engine
Once you've got an idea which rotating assembly you want, the only other major item to put thought into is the cylinder heads. We're not going to dictate what makes a good head and discuss all of the options out there for LS-series engines (see our "Gen III/Gen IV Cylinder Head Buyers' Guide," Jan. 2006). There's just too much to it. What's important from a do-it-yourself perspective is this: combustion chamber size (cc). Along with head gasket thickness, piston valve relief pocket cc, and a couple other factors, this will determine your compression ratio. A cylinder head and a rotating assembly should be chosen at the same time, since not all heads can be had with all combustion chamber cc's. We won't get to install our heads in this segment, but expect an in-depth discussion of cylinder head selection, as well as a helpful sidebar on compression ratio and how to calculate it, soon!
Beyond rotating assembly and cylinder heads, there are other miscellaneous items you'll need, like a camshaft, valve lifters, timing chain, oil pump, and so on. Some of these components can be reused if dictated by a particularly tight budget. We'll discuss these other items in the photo captions and sidebars as we go along. (But we won't get to most of these extras until next time, when we'll also have a complete rundown of all parts used and tally up the cost.) Just remember, we're not doing anything crazy here: just a dependable, streetable build without blowing too huge a wad of dough. With these emphases in mind, let the fun begin!
Now that we've checked everything out in terms of measurements on the block, it's time to start our final block cleaning. Begin by inspecting all threads in the block, both in terms of bolt holes as well as holes for oil gallery plugs. Look for leftover sealant as well as any damaged threads. We discover that our head bolt hole threads are pretty gummed up from the thread compound GM used when originally assembling our LS1. This could interfere later on with proper installation of our ARP head studs, and could also prevent proper torquing of head bolts (if used in lieu of studs). | 
Conveniently enough, ARP sells a tool specifically for cleaning head bolt hole threads on LS1 engines (discussed in the tools article elsewhere in this issue). The tool works just like a tap and can be turned with either a 1/4 open end or a tap turning tool from a tap and die set. Treat it just like a tap: turn it in slowly, and back it off every few turns to help loosen the goop on the threads and prevent jamming the tool. | 
Look at all the crud that comes out of each head bolt hole! Between holes, clean the tool with Brakleen and then shoot it with WD-40 for lube before you hit the next hole. You can probably just ask your machine shop to do this thread cleaning process for you if you don't mind paying a bit extra (there are 10 M11 holes to clean per head and it takes a little time). |
With all threads in the block inspected and cleaned as needed, it's time to give the block a thorough washdown. These two types of solvent (normally used in paint prep) will come in handy for our purposes as they work very well at cleaning metal. Mineral spirits will be used for general cleaning of the block and all metal components we install, and the more-potent 100 percent virgin acrylic lacquer thinner will be used to clean the cylinder walls just before we install the pistons. | 
Put the block on the floor with the front facing downward. Use a clean funnel and pour mineral spirits into the hole formerly occupied by the barbell restrictor. The main oil gallery runs all the way from here to the front of the engine, so mineral spirits will begin leaking out of any hole that isn't currently capped with an oil gallery plug (our machine shop had removed a few of ours). Also dump some mineral spirits down the passages that feed the valve lifters; they're located just above the camshaft bore. | 
Remove the oil gallery plug at the driver side front of the engine block if you haven't done so already. Shine a flashlight into this hole and look down the oil gallery passage to double-check that no debris is present. After you've done this and are confident the passage is clean, you can put the block back on the engine stand. |