The pushrods and valve stems looked perfect and the lifters seemed solid, but there was significant wear in the rocker arm fulcrums. Sure enough, the rocker arms on the no.2 and no.6 cylinders had significant sideplay and most of the others also seemed sloppy. Time to pull off the valve cover and explore. Using a stethoscope, it was obvious that the noise was coming directly from under the valve cover and it sounded homogenious. Shaft-mounted roller rockers like the Yella Terra units are inherently more stable because they cannot rotate axially, so these applications don't require pushrod guideplates.Īfter running my 4.6L stroker engine for over 30,000 miles with the stock stamped steel rocker arms, the engine started to make a noticeable ticking noise especially from idle to 2500rpm.
JEEP CHEROKEE YELLA TERRA ROCKERS PLUS
Stud-mounted roller rockers can rotate on their axis (the studs) and therefore require pushrod guideplates to maintain valvetrain stability plus hardened pushrods that won't wear in the guideplates.
JEEP CHEROKEE YELLA TERRA ROCKERS FULL
Unlike stock stamped steel rockers, roller rockers maintain a constant indicated rocker arm ratio throughout the full valve lift because the center line of the roller stays constant and only its contact with the valve stem center line changes. The reduction in friction with roller rockers has additional benefits of reducing the operating temperature and foaming effect of engine oil to provide a cooler running engine. The use of needle roller bearings at the rocker fulcrum combined with a roller tip at the valve greatly reduces horsepower robbing friction in the valve train to provide a measurable power increase over standard rocker systems. The roller tip on roller rockers eliminates this side loading action. This inside force leads to irregular and rapid valve, valve guide, and valve seat wear in many engines. The traditional metal tip on standard rockers literally drags across the valve tip as the rocker opens and closes causing high side loading on the valve. A high rate of fulcrum wear, flexing, cracking, splitting and breakage are common problems that will result in power loss or possible piston failure due to detonation of the incoming air/fuel charge. Stock pressed steel rocker arms are prone to failure in high performance applications. Roller rockers are infinitely stronger than stock stamped steel rocker arms and are more resistant to bending and breakage under high spring pressures at high rpm. Yella Terra Roller Rocker Installation Jeep 4.0L Engine Yella Terra Roller Rocker Installation Jeep 4.0L Engine
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