The time has finally come: ever since we began this LS1 stroker build in our August 2006 issue, we've been forcing readers to hold their collective breaths; the completion of our hands-on, home-grown engine still months away. With a bulletproof Lunati rotating assembly, bumpy-yet-streetable Lunati Voodoo cam, and high-flow 11-degree heads from ET Performance, we've held high hopes for this garage-built mill. These expectations have extended both to performance output, as well as our ability to successfully demonstrate how a driven do-it-yourselfer can save some dough and reap a bunch of satisfaction by assembling a hi-po Gen III with his own two hands.
When we left you last time, we'd bolted this new 383-inch motor into our 2001 Trans Am and were just about to hit the starter. We've done that, and having completed a thorough break-in, went ahead and got some dyno and preliminary track results for you. We've also added up the dollars spent on this project, and have done some research in an attempt to draw some comparisons to other options for stroking your ride. All of that information will appear below; but first, in the do-it-yourself spirit of this story series, we'd feel the job wasn't complete if we didn't give you a few final hints and tips for engine startup, break-in, and tuning. After all, our target audience has been readers who may be looking to tackle their very first engine build--these issues all go along with the territory. In the spirit of following the path that typical do-it-yourselfers may trod, read on!
FIRE IT UP--WITH CARE
With any newly installed engine, there's bound to be one or two issues to resolve right off the bat--and they might surface before the engine is even fired. Care must be taken that any problem be identified and dealt with immediately, lest you risk damage to your engine--or yourself. So before you bump the starter motor, be sure to:
* Take one last look that oil, coolant, and other fluid levels are topped off.
* Turn on the ignition; look for any arced wires, and listen for anything suspicious.
* Cycle the fuel pump a few times to build pressure in the fuel rails; check for any leaks. Both sight and smell are key here. (If you've just installed an aftermarket fuel rail system, don't be surprised if some of your AN fittings need to be tightened a bit more.)
* Have a fire extinguisher and battery disconnect wrench close at hand--you can never be too safe!
The moments just before a new motor is first fired are possibly the most nerve-racking in any engine build; but if you've taken the time to do things right, chances are excellent that you'll be home free. With the above final items checked, turn the starter--so long as basic provisions like fuel injector size have been addressed in the PCM tune (we'll get to all that momentarily), the engine should start up and run immediately. Watch that oil pressure comes up within the first few seconds--this is absolutely essential. (If it doesn't, stop and find out what's wrong!)
With the motor running, don't just start driving around, as you're not quite in the clear yet. As the engine starts to warm up, continue to watch for fuel or other fluid leaks--metal and fluid changes that occur with rising temperature mean problems that don't show themselves immediately could quickly and without warning cover the garage floor with liquid. As soon as the coolant reaches full temperature (indicating that the thermostat has opened), turn the engine off and let it cool to the point where you can open the radiator cap. Top off the coolant as needed; this may need to be done a few times. Also during this initial engine run time, listen for anything mechanical that sounds strange, like lifters that haven't been able to pump themselves up; it never hurts to shut things down and wait a few moments for oil to dribble into where it needs to be rather than run a lifter dry and risk damaging it.
Our initial startup experience was relatively trouble-free, other than a mysteriously dropping coolant level, which turned out to be due to a bad radiator cap. No abnormal noises were heard emanating from under the hood, and we immediately noticed that our 383 exhibited a lopey idle that definitely did not sound stock. So much for a sleeper! We also took note that with our high-volume SLP oil pump circulating the lifeblood of the engine, plenty of oil pressure was at hand--always a good sign in a brand-new engine. Having passed these initial checks, all systems are go--we're ready to start driving and getting this engine broken in!
THE BIG BREAK-IN
OK, so it runs--good work! But your big-cube engine isn't quite ready to impress your buddies on joy rides, much less hit the local drag strip--and we're not just talking about making sure the tune is dialed-in (more on that momentarily). Anyone who knows the least bit about automobiles has heard the shpiel that new engines need to be "broken in." Going through this procedure ensures optimum power output and long component life, but what exactly is going on here, and what's important to know for the Gen III?
During the first several hundred miles of operation, the metal parts of the engine "mate" to each other. While advances in technology mean that engine parts are manufactured to more exacting tolerances than ever before, the microscopic uniqueness of any one piece of metal that comes off of the assembly line or out of a machinist's cylinder honing machine continues to endure. Think of this mating like the last step in machining: all surfaces that contact one another "wear" or "finish" each other to the point they'll operate at for the rest of the life of the engine. We want this initial wear-in to occur, but if we try to get it to happen too fast, the engine parts will instead wear out prematurely.As far as GM small-block engines go, allowing flat-tappet lifters to properly mate with the camshaft lobes was a huge concern back in the day. This necessitated special lubricants, and also required the engine to be spun above a minimum rpm for the moments following initial start up. Happily, those days are ancient history, and thanks in part to this advance, no elaborate, "ceremonial" break-in is required for an LS1-based engine. But our beloved V-8s still have important parts like bearings--and most significantly, piston rings--that require a wear-in period to operate properly.
So, how to go about this? We spoke to Mark Chacon, Lunati's East Coast Regional Rep., about his thoughts on this issue. "As motors are breaking in, and in regards to piston ring seal, they want a constantly changing engine rpm environment. This is why city driving is generally the optimal condition for any motor break-in. The worst thing that you can do with a new engine is to put it together, fire it up, and then head down the interstate with the cruise control on. While a little bit of freeway driving is OK, certainly for the first 500 to 1,000 miles I would try to avoid long trips or periods where you're operating at a constant engine speed," says Chacon.
OK, so staying at any one engine speed is bad, but this isn't to say you can go take your new engine to six grand the first time out. On the contrary, restraint must be used to keep engine speeds and loads reasonably in check. "Don't go out there and just hammer through the gears all the time; you need to be a little more conservative about how you drive the vehicle. A varied range of rpm usage, combined with keeping it easy on the motor, allows the face on the ring to do a better job of seating to the cylinder wall," says Chacon.
The type of fluid used during break-in is also important. You may have heard that synthetics are "too good" to use during the first miles on a new engine, and this is true. The main reason for this is the piston rings, which as we have said need time to seat to the cylinder walls properly; if they don't, horsepower and efficiency will be left on the table thanks to reduced cylinder pressures. Mark Chacon elaborates: "The ring face must have ample time to break in to the cylinder wall finish, and running a conventional oil for the first 1,500 miles or so will aid this. Ring seal needs to be firmly established before synthetic is introduced into the motor, and one of the reasons the factory LS1 has such a heck of a time with ring seal to begin with, in my view, is that many come from the factory with synthetic oil in them. Once you put synthetic in, what you've got is what you've got, and the rings may never really wear to the cylinder walls. Of course, feel free to eventually switch to synthetic because of its better properties, but make sure the rings have seated fully first; short of using a cylinder leakdown tester, mileage accumulation is the only way to tell whether this has occurred."
As engine parts wear in, more small metal particles are being cast off into the engine oil than would usually be expected. Therefore, keeping the engine oil clean during the break-in period is essential. In furtherance of this, be sure to use a high quality, high capacity filter that can capture very fine particles. As to fluid change intervals, a good rule of thumb from Lunati is to drop the oil after 100 miles to get the initial bearing cast-off material out of the system. Then, change the oil after 500 miles, and again after 1,500 miles have accumulated, from which point forward you can follow manufacturer-recommended change intervals and swap to synthetic oil if desired. Stick to these simple driving and engine oil maintenance tips during the break-in period, and you will help your stroked LS1 live a long, happy life under your GM performance car's hood.