Originally Posted by glennsea
I need to remove the intake manifold to check for a collapsed lifter or broken CAM lobe.
The one thing that I am not sure about is I have to remove the dist and then turn the engine over manually to check. My thougt is to index the dist straight to the rear and mark the firewall, remove it, then remove the manifold, then reinstall the dist on the index.
At this point I should be able to rotate the engine and watch the lifter to see if it moves. If it move, it is collapsed, if not broken lobe.
Will the method work and am I missing anything?
I'm assuming you have miss fire, rough running, or noise that makes leads you to look into whether the cam is getting valves off their seat.
The first thing to check is whether the valves are being actuated and if so by how much. This is a somewhat messing proposition where the engine is run with the rocker covers off. You can make some aluminum foil covers to catch as least some of the flying oil. If this is a Chevy or other engine that feeds top end oil from the push rod, this stuff really can fly.
The first test is of general observation, do all the valves open and close. the next is a bit more detailed as you look for amount.
Determining why if any don't actuate correctly or sufficiently is the next step. It's best to start at the top and simple and work down. First you're looking for a bad rocker and how well it addresses the valve stem. With that comes the pivot, A Chevy would be using a ball and socket arrangement retained by a nut on a stud. Other brands could be same similar to rockers bushed on a shaft. You're looking for wear and structural failures. In the case of ball and socket types that usually is cracks and splitting in the socket or damage to the ball. Where the rockers are on a stud, you're looking for looseness or bending of the stud. For rockers on a shaft it's usually wear of the bushing.
Then pull the push rod from the subject cylinders and check them for straightness and end wear. If you've found nothing to this point it's now time to dig deeper. This is where the intake comes off and for most modern designs that means the distributor comes out. That should start with pulling with a wrench or bumping with the starter to bring the damper's timing marks to the zero degree point Top Dead Center or (TDC). The damper passes this spot twice in a complete engine firing cycle. Once for the number one cylinder and again for the cylinder directly opposite number 1 in the firing order, for a Chevy that would typically be number 6. You need to mark two things for installation alignment on is the location of the housing and the other the rotor. The gears that drive the distributor are spiral cut and there is usually an oil pump drive on the bottom. The former will cause the rotor shaft to rotate upon removal and installation, this can play havoc with your senses, thus the requirement to locate and mark carefully before removal. The latter headache will be the oil pump drive, it will move a bit with distributor removal often making re-engagement and testy enterprise. For a Chevy a long screw driver can be used to rotate the pump drive till all this comes together. Chevy and Ford use an intermediate shaft between the distributor and the oil pump, you do not want this to come out, getting these back from on top is a real exercise.
Removal of the offending lifter will tell you whether you're looking at a failed plunger which would be it's internal valve mechanism or whether the cam has lost a lobe. If the bottom of the lifter is scored up and cut concave, you can be sure the cam lobe under it is also gone. At that point you're going to have to loosen the oil pan and remove the front timing cover as well as remove the radiator, water pump, maybe the grill to get enough space to pull the cam out. None of this is very pleasant at this level.