For the past two months, we've taken readers on a detailed ride through a full-on LS1 engine assembly. In Part 1 of this homegrown motor build series ("My First Stroker," Aug. 2006), we prepped our block and installed a Lunati rotating assembly. With a 4-inch stroke and .005 cylinder hone, we came out with a 383 ci short-block. Our second segment ("My First Stroker, Part 2," Sept. 2006) showcased everything from our Lunati Voodoo camshaft installation to compression ratio calculation, and ended with bolting on our 215cc ET Performance cylinder heads. In both of these stories, we'd done our best to highlight all of the tips and tricks needed not only for Gen III engine assembly, but for adapting the stock block under the hood of your late-model ride to accept stroker internals and other high-performance parts. We've kept focus on holding a reasonable budget while upping the fun with a serious but manageable project for the do-it-yourselfer.
And now, the excitement continues: in this segment, we'll finish off the engine assembly and get our big-cube LS1 installed into our project Trans Am, making it ready to fire up!
We start with bolting the rest of the valvetrain atop our garage-built mill. Though it's possible to reuse the stock LS1 rocker arms with our ETP heads, they simply aren't up to the task of handling large spring pressures. Their particular stud-mount design-aside from being non-adjustable-isn't ideal for the prevention of valvetrain deflection and geometry change under engine operation. Even worse, the rocker stud diameter is only 8mm (equivalent to a tad more than 5/16 of an inch)-a far cry from past GM small-block engines, which normally had 3/8- or even 7/16-inch diameter studs. We decided to go with the ultimate in valvetrain stability: shaft mount rocker arms. See the sidebar on the fully adjustable Jesel rockers we chose for this build.
Pushrod Length Determination
Once a rocker arm is chosen for a given engine, the final piece of the valvetrain puzzle that must be ironed out is the pushrod. This item transmits the movement of the valve lifter to the rocker arm, but it needs to be just the right length or else valvetrain geometry will be wrong. This situation will lead to accelerated valvetrain wear, reduced horsepower, and parts breakage; with the length of the pushrod in error more than a few hundredths of an inch in either direction, it will even make the rockers physically impossible to install. Each engine's unique combination of camshaft, lifter, head gasket, block deck height, cylinder head, valve stem length, and rocker dictates a unique pushrod length that needs to be physically measured with extreme care. Therefore, the right pushrod for an engine cannot be accurately known until the engine is nearly fully assembled. The measuring procedure is fairly straightforward, and like we have with the rest of this engine build, we're going to take you through it step by step. We'll show you this process as performed on cylinder number one, but you should repeat these measurements on at least one other cylinder on the opposite cylinder head; you never know when machining tolerances on various parts might create different pushrod needs for different cylinders (though this is uncommon).
Pushrod and Rocker Arm Installation
With our required pushrod length known, it's time to order up a good set of pushrods. Once they are in hand, we can install and adjust the rocker arms to Jesel and Lunati specifications, completing our valvetrain installation.The basic rocker adjustment procedure for each of the LS1's cylinders is the same one hot rodders have used for decades. (Note that the 2-crank-position rocker adjustment procedure outlined in the GM service manual will only safely work for cams with small durations.) First, bolt the rocker assembly on while both valves are closed, i.e., a bit after the intake valve closes. Then, keeping a close watch on the movement of the rockers, rotate the crankshaft until the exhaust rocker just begins to open the exhaust valve. At this point, the intake rocker can be adjusted-since we're at the very beginning of the exhaust stroke, we know the intake valve can't possibly be opening yet. Then, rotate the crank until the intake opens and then almost completely closes. At this point, we can safely adjust the exhaust rocker, as we know the exhaust closes immediately after the beginning of the intake stroke and will stay so for some time.This adjustment procedure is much easier to do on an engine stand than it would be with the motor installed in a car, and happily, it's a one-time-only task for a hydraulic lifter cam. Think about this: a camshaft with solid lifters would not only have to have its rockers periodically readjusted, but it would have to be done while the engine is hot!
TOPPING IT ALL OFF
With the rocker arms on and all valves adjusted, we've completed the last step in the assembly of our engine internals. It's now time to cover up our stroked LS1 and add new items like ignition coils, a higher-flowing intake manifold, and an underdrive crank pulley. Along with modifying a few stock components along the way, this will get us ever-closer to reinstalling the engine into our patiently waiting Ram Air Trans Am.
Valve Cover Modification and Installation
We were all ready to cap off our ET Performance heads by putting the valve covers on, but then we hit a bit of a setback. Despite the added clearance afforded by ETP's raised valve cover rail, we found that our stock valve covers wouldn't go on. Not only did nearly all of the rocker adjuster nuts hit the oil deflectors on the underside of the covers, but the baffling and bracing under the covers also interfered with our Jesel rockers' shaft-mount system.
We immediately ruled out springing for a set of aftermarket valve covers (and their accompanying coil relocation kit) because of cost and packaging concerns. Beyond this option, valve cover spacers are another common solution to the rocker-clearance issue. By lifting the stock valve cover further off of the cylinder head, added space is afforded for the valvetrain. Though readily available from several different manufacturers, we didn't want to use them for a few reasons. First, valve cover spacers are an added expense, costing a couple hundred bucks or more (remember that we're keeping an eye on our budget). More significantly, the geometry of our ignition and nitrous systems would be affected: we simply didn't want to run the risk of plug wires not reaching the spark plugs, direct-port nitrous lines having to be bent at extreme angles, the wiring harness having to be lengthened, and other possible issues associated with raising the valve covers even further than ETP already had. (And as we'd discover later, spacers wouldn't even have worked in our F-body; they wouldn't have allowed our ignition coils to fit between the valve cover and the plastic box surrounding our A/C evaporator!)
With these concerns in mind, we reluctantly decided to ditch the factory PCV system and gut everything under the factory covers in hopes of getting them to fit. Environmental pollution concerns aside, losing this probably isn't a bad thing since the LS1's sub-par PCV system is known to contribute to oil consumption, and excess oil vapor entering the engine can also cause detonation problems. We'll show you how we substituted for the PCV system in a moment; but for now, let's take a look at the factory valve covers and how to mod them up.
The Gen III uses a cast aluminum valley cover that installs into the area atop the engine block between the cylinder heads (traditionally known as the "lifter valley," though the LS1's lifters are not really visible in this area). Unlike past generations of small-block, where hot oil from the valley area would splash onto the underside of the intake manifold, the LS1's valley cover isolates the intake manifold completely from all the hot stuff inside the engine. This contributes to a cooler intake and consequently a denser incoming air charge, as well as improved oil sealing (the front and rear of the intake were notorious locations for leaks on earlier small-blocks).
The higher horsepower numbers that come from a stroker are only possible if one can reliably light the fires that burn over 50 times per second in each cylinder. While the LS1 ignition system is quite good from the factory, we decided it wouldn't hurt to make a few upgrades, especially considering that we'd be throwing some nitrous into the mix down the road. (See the sidebar for more technical information on this topic.) That said, let's show you just how these upgrades are installed.
One of the last remaining items that must be installed before we can drop our stroked LS1 into the engine cradle is a rather basic one: the engine (or "motor") mounts! The stock mounts will be reused, but we treated ourselves to an ARP bolt kit (PN 434-3102, $22.50) consisting of stainless steel, hex-head bolts.
While engines of years past utilized a crank pulley bolted to the front of the engine's harmonic damper (often referred to by the misnomer "harmonic balancer"), the Gen III has a one-piece harmonic damper with machined surfaces for the accessory belts to ride on. While it's possible to reuse a GM unit on a stroked LS1, we're going to take a page out of the classic hot rodding manual and replace it with a smaller-diameter "underdrive" unit from SLP. By allowing the power steering pump, water pump, and alternator to turn more slowly for a given engine speed, fewer horsepower are lost and accessory life is increased.
It seems like a no-brainer, but thanks to its press-fit design, installing the crank balancer can be one of the most strength-demanding portions of an engine build. Tools are available-or can be improvised-that help you gain the mechanical advantage you need to slowly press the unit into place. But unfortunately, they all involve turning in the direction of crank travel-meaning the crank will want to rotate and work against you. A GM J 42386-A Flywheel Holding Tool (or similar unit that bolts in place of the starter motor) is a good idea as it will keep the crankshaft from spinning and make your life a lot easier.
Absent your access to such a tool, there are some other options to help make sure you'll be able to get the balancer on without simply turning the engine over. For example, you might choose to install the balancer before the rocker arms go on: put in the spark plugs, and all eight cylinders will have sealed pockets of air in them to resist piston movement. But since we have already installed and adjusted our rockers, we'll get the balancer on as far as we can; then, if need be, we'll wait until the transmission and driveshaft are hooked up to tighten the crank bolt the rest of the way (they'll help resist crank turning significantly).
The Lunati crankshaft-though it has a keyway slot for the oil pump drive-is not machined for the use of a keyway to help locate the harmonic damper. While such an additional keyway is only really necessary for supercharged applications, it would have been nice if Lunati had pre-machined its crank for one, especially since most aftermarket harmonic dampers have a corresponding slot ready. Though the damper is neutrally balanced, we'll still do our best to line up SLP's would-be keyway slot as close as possible to the Lunati keyway further back on the crank snout. In this way, the SLP-engraved timing markings on the outside rim of the balancer will be at least roughly close to where they ought to be (although a need for a timing light is an unlikely scenario on the electronically controlled LS1).
There are a few cooling system items to install onto our LS1 before the engine will go into its home under the hood of our project 2001 Firebird. These primarily include the water pump and thermostat.
As to the water pump, we're reusing the stocker, but an upgrade to a new GM water pump is not a bad idea if your vehicle has a lot of miles on it. This isn't your only option though: you may want to upgrade to an aftermarket mechanical water pump or even swap to an electric pump for reduced parasitic drive losses (it purportedly takes less energy to turn such a pump electrically than it does to spin a pump mechanically). But this author simply can't be convinced that an electric pump can ever be as reliable as a mechanical pump. Combine this street-minded attitude with the interest of cost savings, and we're going with the GM pump.
The thermostat is a cooling-system item that hot rodders have swapped out for decades. With any high-output engine, a cooler thermostat should be used to help ward off detonation. While the stock 195-degree unit is good for emissions and winter warm-ups, it's not so good for horsepower.
Intake Manifold and Throttle Body
The increased cubes of a stroker are worthless unless the intake system is able to provide enough flow to fill them up. Early-model LS1 engines with the original LS1 intake manifold are in serious need of a higher-flowing intake; later LS1s had the LS6 unit, which flowed much better. But even this intake can't match the flow capabilities that aftermarket manifolds afford with their larger runners and increased throttle body openings.
There are quite a few intakes on the market that will work on an LS1, but very few that are composite (and hence virtually impervious to the heat soak issues that plague aluminum and steel manifolds). While our stock LS1 had previously been upgraded to a composite 78mm F.A.S.T. LSX intake manifold (see "F.A.S.T. On The Gas," Jan. 2006), even its larger-than-stock throttle body opening could prove restrictive now that we're running 6.3L of displacement. Fortunately, F.A.S.T. makes it easy to upgrade its LSX intake and sells its 90mm top shell separately, avoiding the need to purchase an entirely new manifold. We also need a bigger throttle body to match, and so looked to Holley for a new LS Series unit (since the Holley throttle body does not include a new seal, we ordered a 90mm one from F.A.S.T.: PN 30-54011, $9.27). Conveniently, all of these items can be installed while the engine is still on its stand.
Intermission! Dropping the Engine into the Subframe
We've reached the physical limit of bolting parts onto our LS1 while it's still on the engine stand: the reality of having to attach a chain to the engine in order to lower it into an F-body's subframe means that items like the fuel rails will have to wait, lest they be accidentally broken or damaged. Once the engine is secured in the subframe, though, more can be done to get it ready to be inserted into the car with relatively little difficulty.
Now is also a good time to install little items you might not have transferred to the new engine yet. For example, the ECT sensor screws into the front of the driver side cylinder head and a plug goes into the same hole at the rear of the passenger side head. Put the oil filter on if you haven't done so already. You should also put in place-even if loosely-all fasteners you removed when taking the engine out of the car and stripping it to the block. For example, there are several attachment bolts for ground straps on the heads and engine block. Hopefully you've labeled all of this stuff when you took everything apart so you know what goes where! It's easier to do all of this now as access to some areas of the block will be restricted once the engine is sitting in the subframe (also known as a cradle).
With the engine in the subframe, we can continue installing components onto the engine, and we begin with the fuel rails. Avid readers will recall that this vehicle has already been upgraded with a Racetronix fuel system, including pump, wiring harness, and 60 lb/hr Siemens/Mototron fuel injectors (see "Fuel: Up!," April 2006). This system will be able to provide all of our necessary fueling, even if we have to wire in a pump voltage booster to be able to safely handle large amounts of nitrous injection.
But we're looking at 450-500 rwhp naturally aspirated, and likely an eventual 200hp shot of nitrous on top of that. Also taking into consideration that our ZEX nitrous system is designed to receive fuel from a fitting on the fuel rails, we wanted to make sure the rails were large enough to accommodate all of this flow. We called Speed Inc. and ordered an LS1 fuel rail kit; follow along as we bolt it on.
Modifying the PCV System.
Since we had to cut the PCV baffles out of the valve covers in order to provide adequate clearance for our valvetrain, the system can no longer be used without gobs and gobs of oil entering the intake manifold. Though technically the PCV system is an emissions piece that should not be altered without incurring the wrath of the EPA, in this case we had no choice. Here's how to go about it.
INSTALLATION OF THE ENGINE INTO THE VEHICLE
We're about done with this segment of the story, but wanted to leave you with a few final tips and tricks on installing the LS1 into the engine bay of the ever-popular Fourth Gen F-body. It's not as hard as you might think, and the engine-in-cradle system means a good chunk of your drivetrain, wiring harness, and exhaust system can attach to the motor before it's installed, saving much of the shaved knuckles and cursing that invariably come from working in cramped underhood quarters!
Rock and Roll, MoHawk and all: Jesel's J2K Rocker Arm System
Theoretically, you can pick up a set of rocker arms for your LS1 for a few hundred dollars-or even reuse the stockers if you're brave. But before getting yourself up in arms (no pun intended) about the price of a Jesel shaft rocker system, know this: it'll help your engine last longer, operate more safely, and make more horsepower. Sound like a lot to expect from a rocker arm set? It is-and Jesel delivers. Rocker arm design is a complex science, but we'll try and hit the highlights so that you can make an informed buying decision regarding your next set of rockers.
Stud-mount rockers have been a part of the small-block "Chevrolet" since the very beginning, and the Gen III continues the tradition. As we have stressed many times over, GM engineers did one helluva job on the factory LS1, and their design choices resulted in an engine with nary a fault. But despite all the modern technology they incorporated, one area they didn't change much was the old-school stud-mount rocker system. More than likely, the bean counters upstairs just wouldn't allow a better, more-costly-to-manufacture design through their stingy hands. The engineers did the best they could and came up with a single-plane geometry for the valve, rocker, and pushrod, as well as a stand mounting system and rollerized fulcrum for the rocker itself. The result is a valvetrain that has overall performed admirably for the emissions-friendly, low-lift camshafts of factory engines-despite some reported dark spots of bent pushrods and broken rocker arms. The problem arises in that stock-style stud rockers simply can't stand up to the demands of greater engine speeds and valvespring pressures without incurring the above-mentioned penalties in engine longevity and power production. We spoke to Jesel's Rob Remesi about the advantages his company's shaft rockers provide.
"When the Chevrolet small-block V-8 was introduced in 1955, one of its most highly touted features was its lightweight, high-revving ball and stud stamped steel rocker design," says Remesi. "This stud rocker setup served performance and racing enthusiasts for years before it became overstressed and Band-Aids started to appear. The first modification made was to install polylocks, which allowed one to maintain valve lash longer and adjust the hydraulic lifters so that they didn't pump up at high rpm. Then, as more aggressive cam profiles surfaced and valvespring pressures increased, press-in studs started pulling out of their bosses. Chevy came out with screw-in studs that didn't pull out, but their small diameter allowed them to flex too much. The fix was larger screw-in studs made out of stronger alloys. But as spring pressures continued to escalate, they too would flex, so stud girdles were invented to tie all of the studs together, mimicking the solid shaft-type rockers found on Chevy's sister division engines like Cadillac and Buick.
"Many engine builders are still struggling today with stud rockers, girdles and polylocks-antiquated parts that have no place in a modern performance engine. Dan Jesel started his company to provide the best quality rocker systems for the performance racing industry as well as the weekend warrior, and he is credited with inventing the first effective aftermarket shaft rocker system. He designed stands that bolted to the standard stud bosses, yet relocated the rocker pivot point any distance he desired away from the valves. That's the crux of the entire stud versus shaft debate-you can't change the rocker pivot length and correct the rocker geometry unless you move the pivot point. So, no stud rocker can perform as well and as reliably as a longer pivot shaft rocker-it's that simple. Shaft rockers are more stable at high rpm-ensuring accurate valve timing events-and are mounted to the head using a steel stand that positions the roller directly over the valve tip. Meanwhile, a stud rocker is aligned by the stud location and the pushrod and guide plate (as applicable)-not the best for holding the rocker where it is supposed to be-resulting in additional frictional losses. Reduced valvetrain friction equals more power and longer component life, regardless of valve lift or rocker ratio," says Remesi.
Jesel's J2K series is the latest and greatest iteration of the company's technology. The rockers' so-called MoHawk beam is claimed to be the lightest and strongest rocker design on the market, resulting in the lowest possible moment of inertia (a measure of how much of an object's mass is actually in motion as it moves or pivots). This not only increases the rpm an engine is capable of, but also lengthens valvespring life. "The components used in our rocker set for the ET Performance LS1 heads are the same components that we used to build the rockers for the Katech-built C6R engine that just won the 24 hours of LeMans," says Remesi. "When a rocker set is shipped from our facility, we don't know whether it is going to be used on a race engine or a street engine. There is nothing better than on-track testing to prove the durability of engine components; you can rest easy knowing the same Jesel parts that are going into your street LS1 have just been proven in one of the world's most grueling endurance races!"
Hopefully, you can start to see that when you weigh in the benefits a Jesel shaft rocker system provides to your engine, the investment is a darn good one.
We Have Ignition!
When introduced in the 1997 Corvette, the LS1 featured many major changes from past small-block engines, and one of the most significant was its coil-near-plug ignition system. After the LT1's notorious OptiSpark featured just the previous model year, the LS1's one-coil-per-cylinder system was no less than a revolution in terms of GM V-8 ignition. But like all things found under the hood of a GM performance car, we love to modify and improve-no matter how good any one factory system might be. That said, upgrades are available on the market to make the LS1's ignition system perform even better.
By definition, for an equivalent displacement engine to make more horsepower, you must increase cylinder pressures. Hi-po parts like better-flowing cylinder heads, large-runner intakes, and wilder cams all help jam more oxygen and gasoline into the cylinder, which, when lit, create the enormous spike in pressure that presses down on the top of the piston, twists the crank, and sends torque to your rear wheels. But the denser the air-fuel charge is, the more difficult it is to properly ignite-and adding nitrous oxide to the mix only compounds the problem. This science holds equally true whether you're dealing with a stock-displacement engine or a stroker motor like ours.
One of the major players offering components to up the output of Gen III ignition systems is MSD. The company now offers higher-output coils to further enhance the LS1's fuel-mix-igniting ability. Here are the coil specs for all you techno-freaks out there: a turns ratio of 52 to 1 acts with a primary resistance of 0.57 ohms and a secondary resistance of 3,100 ohms to yield a peak current output of 150 milliamps. Combined with a spark duration of 1.2 milliseconds and a maximum voltage of 44,000 volts, these coils purportedly put out three times the spark energy of the stock ones. But let's not forget that these coils also produce the multiple sparks from which MSD Ignition takes its name. According to MSD's Todd Ryden, "the multiple sparks don't necessarily increase horsepower, but add significantly to the drivability aspect of the vehicle. They help provide a good idle, quick throttle response, and will also assist in supercharged or nitrous applications." Lower emissions and increased fuel mileage are certainly no bad thing, and MSD's system helps ensure a complete burn of the air/fuel mix under any engine condition imaginable.
The perfect complement to these coils are MSD's Super Conductor plug wires, which spec out at less than 50 ohms per foot (factory wires are normally in the vicinity of 1,000 ohms per foot); so very little energy is lost as current travels to the plug. Despite this small resistance value, MSD's special winding procedure for the copper alloy conductor and its ferro-magnetic impregnated core yields only a tiny fraction of the electromagnetic interference (EMI) emitted by other aftermarket wires-shielding your radio and other devices from static. The wires also feature a dual-crimp terminal and use a proprietary silicone/synthetic-blend boot material for the ultimate in strength and heat resistance.
With products from MSD guaranteeing a powerful spark under all operating conditions, we have no worries about our ignition system being ready, willing, and able to light some serious fires within the bores of our 383 LS1!