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!
Once clearance is checked and verified to be OK, the valve covers are thoroughly cleaned of all metal shavings and set atop the heads. Being sure to use a new GM valve cover gasket (PN 12560696), torque the stock valve cover bolts to 106 in-lb. Turn the crank over at least twice (one cam revolution) and make sure you don't hear any contact under the covers. If it sounds OK and there's no binding as you're trying to turn the crank, you should be good to go! | 
We weren't able to get our hands on a new GM valley cover gasket (PN 12558178) in time for our engine assembly, so we were forced to reuse the stock one. Like the oil pan and front/rear cover gaskets, it's a controlled compression aluminum carrier design like we described in our gasket sidebar last issue. After thorough cleaning of all surfaces, the valley cover is set in place and the bolts torqued to 18 lb-ft. Though ARP has bolt kits available for the valley cover (PN 434-8001, $36.04 for stainless hex-head bolts), we had to use our F.A.S.T.-supplied button-head cap screws which, with their flatter heads, give enough clearance for the thicker-than-stock F.A.S.T. intake to sit above. | 
By virtue of their location in the valley area between the cylinder banks, the LS1's knock sensors are excellently positioned in the block to sense engine acoustics. They look the same as the knock sensors GM has been using since the TPI days, but are specially tuned for the acoustic signature produced by abnormal combustion in the LS1's aluminum-block engine. They are torqued to 15 lb-ft with a 7/8 deep socket. Don't overtighten these suckers, they're sensitive pieces of equipment! The piece of wiring harness that connects to these two sensors must also now be installed as the intake manifold is soon to go on atop them. |