IF, (and this is a big one) the camshaft isn't worn, or the lifters don't have cupped-out bottoms, you should be able to eliminate any mechanical noise from the valves with a good adjustment. A camshaft has what's called an "acceleration ramp" that gradually takes up the slack between the parts before the valve is pushed open. Once all the clearance is taken up, the valve is opened, and closed by the movement of the cam, and it slows down just before the valve meets the seat, to prevent battering the seat on closing. The clearance specification just happens to match the height of the acceleration ramps. If an intake valve has a .006" clearance, for instance, the gradual lift before opening is 6 thousandths. Generally, exhaust lobes have more clearance than intakes, to account for the higher operating temperatures, and the tendency for valve stems to "grow" at normal running temps. Hydraulic cams also have clearance ramps, but they're usually much less, normally about .002" for intake and exhaust.
I like to get an engine up to normal operating temperature, shut it down, and do an engine-stopped valve adjustment. Inline 6-cylinder firing order is 1-5-3-6-2-4 on every one I've ever worked on, so write the firing order down in halves:
1-5-3
6-2-4
The nunmbers above each other are "companion cylinders", where both come to the top at the same time. When #1 is on compression, ready for adjustment, #6 will be at the top of the exhaust stroke, with the exhaust valve closing, and the intake opening, getting ready for the intake stroke. This is called "rocking" where the valves, and rocker arms are moving in opposite directions. Turn the engine by hand and watch the #6 rockers. When they're rocking, #1 is ready to adjust, both intake and exhaust. Make 1/3 turn of the crankshaft, and #2 will rock, and #5 will be ready for adjustment. Every 1/3 turn, another cylinder pair will line up. In 2 turns of the engine, all 6 cylinders can be adjusted. No mess, no splatter, and you can get a perfect adjustment the first time!
Jerry
