They are self aligning, but they have a weird mount onto the heads. The rocker support is 12555582
Here is a pic, they are investment cast roller fulcrum rocker arms
I did a 4.3 to 4.3 swap on a 2000 or 2001 GMC Envoy, the guy found a 2002 4.3.
I had to drill and tap the knock sensor out to a larger size as there was a sensor difference:flat response to resonant senor types. I had a single wire, teh other had 2 wires.
I popped the valve covers off and was suprised to see the roller fulcrum/slide top rocker arms.
The knock sensor is documented here for a 2001 S10 4300 Vortec application. Pretty sure the PCM change was to the 0411 PCM.(I bolded PCM and knock sensor info)
2001 S-10
Brand Identity
The Chevrolet S-10 Pickup continues to expand in versatility. This year, a Crew Cab 4x4 model is offered, joining the likes of the Regular Cabs, Extended Cabs, Long Boxes and Short Boxes (two- and four-wheel-drive varieties). Once again, the S-10 offers the choice of two engines, the efficient Vortec 2200 L4 and the powerful Vortec 4300 V6. In addition, there is a choice of two transmissions, standard antilock brakes, spacious cab and enough cargo room to get the job done.
New for 2001
Models
• 4-door Crew Cab 4x4
Exterior
• Medium Sage Green Metallic replaces Meadow Green Metallic
• Freshened 16-inch x 8-inch aluminum wheel appearance for models with Sport Suspension (ZQ8) (Excludes Xtreme)
• GM Accessories decals and stripes for Xtreme Package (factory-available/dealer-installed)
• Forest Green Metallic is an all-new color (interim availability)
Functional
• Generation III front windshield wiper arms and blades
• National Low Emissions Vehicle (NLEV) system option
• Delco Powertrain Control Module (PCM) replaces Vehicle Control Module (VCM) on Vortec 4300 V6 engine.
• Lower emissions are achieved through the implementation of Enhanced Knock Detection and Spark Correction System "DSNEF"• Programmable door locks
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The roller rockers are noted as a new change for the L35 in this 2001 GM info. This artcle states that teh rocker arms were redisgned for MY 2000. So in and around 2000-2001 the rocker arms were redesigned. In
(I bolded the pertinent info)
"Vortec 4300" 4.3L V6 (L35) Features & Benefits
OVERVIEW
A new Powertrain Control Module highlights a list of refinements in the L35 V6. The low-end torque delivery of an overhead-valve engine, matched with continued improvements in noise, vibration and harshness control and the latest electronic controls keep the Vortec 4300 at the forefront of V6 truck engines.
NEW OR CHANGED FOR 2001 MODEL YEAR
•Powertrain Control Module (PCM) separated from Vehicle Control Module (VCM)
•Detonation Control Improvements
•Air Injection Reaction for Sierra
•Denso Heated Oxygen Sensor for Export to Japan
•On-Road Vapor Recovery (ORVR) System on Jimmy and Safari
•New Cam Bearings
•New Crank Sensor
•New Alternator Ratings
•New Air Cleaner and Mass Air Flow (MAF) Sensor for GMC Savana
•Revised Oil Fill Tube for Chevrolet Express and GMC Savana
•Extended Oil Change Interval for Sierra
•New Starter Motor
•Sleeveless Coolant Sensor
•Improved Manifold Absolute Pressure (MAP) Sensor
CUSTOMER BENEFITS
NEW PCM
The L35 uses a new Powertrain Control Module (PCM) which manages all powertrain control functions. Control of the L35 had previously been left to a Vehicle Control Module, which managed both powertrain and chassis functions, including anti-lock brake systems.
The new 512-kilobyte PCM is mounted on the intake manifold, and communicates with the adjacent VCM via a data bus. The PCM requires revisions to the L35's wiring harness. The customer will notice no change in engine performance specifically attributable to the new control system, yet the L35 PCM offers several advantages over the VCM.
It reduces cost compared to the integrated VCM. More importantly, it gives the L35 the latest-generation electronic controls, and it gives Powertrain full responsibility for engine management. Powertrain engineers developed software for the PCM independently of vehicle platform teams.
The PCM itself incorporates two custom integrated circuits. One controls the fuel pump, exhaust gas recirculation and transmission; the other primarily controls ignition timing and knock sensing. The dual-circuit design trims weight and improves reliability by reducing the number of external wiring connections.
BETTER KNOCK CONTROL
A new "flat response" knock sensor greatly reduces the possibility of detonation, or pre-ignition of fuel before the spark plug fires. Detonation presents itself to the driver as a loud, unpleasant knocking sound and vibration from the engine bay. Mounted at the rear of the engine, the new, more sophisticated sensor "listens" better than the old: It's able to more accurately separate knock from the myriad of sounds produced by an internal combustion engine. The new PCM uses data from the knock sensor to adjust ignition timing accordingly. The flat-response sensor provides the most advanced detonation control available. Combined with the PCM and new crank sensor, it virtually eliminates engine knock regardless of fuel grade.
AIR FOR SIERRA
L35s installed in Sierra pickups with manual transmissions will be fitted with a Secondary Air Injection Reaction (AIR) system. AIR lowers exhaust emissions by injecting warm, fresh air into the combustion process to create an exothermic reaction. The reaction creates heat and warms the catalytic converters more quickly, speeding catalyst light-off and reducing emissions during cold starts--a critical phase in certification tests.
The system requires an air pump, air delivery hoses and solenoid control and shut-off valves. Exhaust manifolds on AIR-equipped L35s are modified with a boss that delivers injected air to the exhaust ports. With AIR, the L35 achieves National Low Emission Vehicle (NLEV) certification in Sierras equipped with manual transmissions. Because of variations in the certification procedure, the L35 does not require AIR for NLEV status in automatic-equipped Sierras.
LOWER EMISSIONS FOR JAPAN
L35s destined for Japan will be fitted with a new Denso oxygen sensor with a 6.6-watt heating element. The sensor reaches full operating temperature more quickly, and equips the L35 to be an "export" Low Emissions Vehicle (XLEV).
ORVR INTRODUCED
The Jimmy and Safari are now equipped with an On-Road Vapor Recovery System. ORVR keeps gasoline vapor from escaping into the atmosphere. The L35 system collects vapor in a 3.1-liter evaporative cannister, and is designed to the stringent .020 inch leak detection standard.
CAM BEARINGS
The cam bearings are manufactured from a new alloy with less lead and more aluminum to improve durability and extend the anticipated useful life of the engine.
ALTERNATORS
The alternator on the L35 is now monitored by the PCM for proper charge rate and operation. The standard alternator in the Sonoma, Blazer, Jimmy, and Safari delivers 100 amperes of output. A 105-amp alternator is optional on the Safari and standard on the Sierra and Savana. Savana's can be upgraded with a 130-amp alternator.
EXTENDED OIL LIFE
New computer algorithms extend the maximum oil change interval for L35s in the Sierra. The maximum permissible interval is 10,000 miles, compared to 7,500 in 2000. The Powertrain Control Module records engine temperature and length of operation at a given temperature, then indicates an oil change when it's actually needed. With new data on real-world customer use, Powertrain engineers have adjusted the software to allow the longer intervals. That means more convenience for the customer and less environmental impact.
STARTER
The new starter motor draws less amperage than the starter used for model year 2000, yet retains the same cold cranking rating. That means equal starting power with less drain on the battery. The starter is also lighter, and costs less to manufacture.
SLEEVELESS COOLANT SENSOR
The coolant temperature sensor uses a plastic insulator to protect electrical leads inside the brass housing, rather than a rubber sleeve. The new sensor reduces the possibility of assembly rejection or shorting in operation.
BETTER MAP
The Manifold Absolute Pressure (MAP) sensor is manufactured to the higher Electro Magnetic Improvement (EMI) standard, which makes it more immune to operational fluctuations in the presence of electrical interference.
CONTINUING FEATURES
The L35's valvetrain was redesigned for model year 2000 to decrease internal friction, reduce noise and improve fuel economy. Low-friction roller pivot rocker arms and roller lifters were introduced. A roller cam chain reduced noise and enhanced durability.
Cam profiles were adjusted to increase low-speed torque without sacrificing high-end horsepower. L35s for California and select states in the Northeast were certified as Low Emissions Vehicle (LEV) compliant.
In recent years, Powertrain engineers have focused on reducing noise and limiting vibration in the Vortec 4300. Accessory mounts have been stiffened. A single-belt accessory drive system with a 100,000-mile belt was developed to reduce both noise and maintenance. The engine block has been stiffened without increasing mass. The cast aluminum oil pan is not only attached to the block, but to the transmission bell housing as well, further increasing overall engine stiffness and limiting vibration. Powertrain's patented sequential central port injection is one of the most precise fuel-delivery systems available, allowing quick starts in all conditions.
With 1 million built annually, the L35 remains one of Powertrain's highest volume engines. It was developed in the mid-1980s by removing two cylinders from the legendary small block V8. A counter-rotating balance shaft was introduced to balance primary crank vibration in the 90-degree block.
"Its basic strengths over the years remain--a balance of good torque, specific output, economy and durability. We've refined it and we're continually keeping it current with things like the flat-response knock sensor." --Ron Meegan, Total Integration Engineer, Gen 1E engines.
LEADERSHIP
The Vortec 4300 remains one of the best V6 engines available. It delivers excellent torque and good specific output in an economical, high-value package, and it continues to surpass increasingly stringent government emissions standards.
"In the Sonoma, the L35 4300 delivers 0-60 mph times under nine seconds... a nice kick in the seat at the low end, and plenty of power for passing or medium-duty towing. It's smooth as pushrod V6s go, and lively enough to spice up a daily commute." --AUTOWEEK'S ULTIMATE BUYERS GUIDE, 1997
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In 2003 after the L35 was dropped in favour of the newer LU3 designation, the 4.3 Vortec V6 went from the CSFI(Central Port Fuel Injection) to the MPFI spider set.
This is the same setup that actually has the injector at the end of the spiders leg rather than a mechanical poppet valve like the 1996-2002 Vortec 305/350/4.3.
GM was replacing teh CSFI units with MPFI units free under warranty for California registered vehicles as Cali gas was wreacking havoc with eth stock poppets. This research led to the V6 wide MPFI injection as the L35/LU3 Vortec V6 lasted past 2010, when teh Vortec 305 L30 and Vortec 350 were dropped when teh newer 1999-2007 GMT 800 trucks came oonline, you could get the 3/4 ton and 1 ton trucks with Vortec 350 for a while, and in teh vans widespread until 2002 and some vans got L31 in 2003. Marine engines used L31 longblocks with the Marine intakes with 25 lb/hr injectors into 2013.
peace
Hog