I have replaced head gasket, cam, rocker arms and lifters in my son's 93 Sunbird. SOHC. No2 intake rocker has broken twice since. Replaced lifter and rocker both times. Car is rapping again and I know No2 is culprit. What could be problem?
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Re: Rocker arm failure
Did the timing belt break at one time? Aside from the obvious of it sounding like your son did what mine did and tried to race the vehicle beyond it's abilities if the timing belt broken at one time it may have damaged the valves. If the valve impacts the cyclinder it is possible that it can damage the rocker and cam. When you pull the head off this time have the head re-worked and valves replaced. This should solve the problem.
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In engines with rocker arm valve systems, the procedure I'm familiar with is to remove a rocker arm cover, and (one at a time!) while the engine is running, slowly back off the rocker arm retainer nut or bolt just until you hear the lifter tapping, then tighten it a quarter turn. If you can identify a lifter that is already tapping, tighten its rocker arm slowly until it stops tapping, then adjust it. Do not over-tighten! This can damage the engine.
Listen carefully to how the engine sounds; if it starts to stumble when you tighten a loose rocker arm, you've gone too far. If you cannot get the engine to run well without tapping, you may have too much wear in the valve train and may be due for a head overhaul, or you don't have adequate oil pressure in the lifters in question.
Repeat until all rocker arms are done. Replace the rocker arm cover using a new gasket, then (in a V-engine), repeat the procedure on the other side of the engine.
Wearing safety goggles, or better yet, a transparent face shield, is strongly recommended. Sometimes oil will squirt out a considerable distance from the lifter side of the rocker arm during adjustment, and the direction is not readily predictable.
There is no such thing as a rocker shaft. There is a cam shaft, rocker arm assembly, Rocker arm, lifter etc. If you are talking about the rocker arm assembly that bolts to the head, it is 58 Ft/lbs. If you are talking about the actual rocker arms, you tighten them till they contact the push rod and the valve stem and then you put oil control clips on so the oil does not spray and you start the engine. You tighten them down till the chattering noise goes away, then back them off 1/8 to 1/4 turn.
Move the intake secondary rocker arm A for the No. 1 cylinder. The secondary rocker arm A should move independently of the secondary rocker arm B.
If the intake secondary rocker arm A moves freely, go to step 5.
If the intake secondary rocker arm A does not move, remove the secondary rocker arms as an assembly, then check that the pistons in the secondary rocker arms move smoothly. If any rocker arm needs replacing, replace the secondary rocker arms as an assembly, then retest.
Repeat step 4 on the remaining intake secondary rocker arms with each piston at TDC. When all the secondary rocker arms pass the test, go to step 6.
Check that the air pressure on the shop air compressor gauge indicates over 400 kPa (4.0 kgf/cm2, 57 psi).
Install a 10 x 1.0 mm adapter to the inspection hole, then connect the air pressure regulator
With the specified air pressure applied, move the intake secondary rocker arm A for the No. 1 cylinder. The secondary rocker arm A and secondary rocker arm B should move together. If the intake secondary rocker arm A does not move, remove the secondary rocker arms as an assembly, and check that the pistons in the secondary rocker arms move smoothly. If any rocker arm needs replacing, replace the secondary rocker arms as an assembly, then retest.
YOU HAVE TO REMOVE VALVE COVERS LOOSEN REMOVE ROCKER ARMS ASSEMBLY KEEP ROCKER ARM ASSEMBLY IN ORDER SO THEY GO BACK IN THE ORIGINAL POSITION.YOU HAVE TO REMOVE INTAKE MANIFOLD ALSO.YOU NEED A REPAIR MANUAL FOR TORQUE SEQUENCE ON THE INTAKE MANIFOLD AND ROCKER ARMS TORQUE.
First, your engine has rocker arms, if you have a 4 cylinder you have 8 rocker arms, and if it is a 6 cylinder you have 12 rocker arms. Now if it is indeed a rocker arm making the noise, the cause is most likely a bad lifter or a worn cam shaft.
You either have had the wrong valve seals installed, they are physically missing, or the valves are incorrect (too loose in the guides/stem too thin). The rocker arm seals will not contribute to your issue. If it did not have the oil smoke before you took the head off, the issue is with whatever the machine shop did. Valve seals have to fit TIGHT, or oil will go down the valve stem into the intake.
Take the head back to the machine shop & tell them to fix it. For free.