Perplexing valve adjustment

I have followed the advice of many of you and obtained the "Z" block and a dial indicator to adjust my valves. When I get the pully in the correct spot, and then place the z block in place, I rock the rocker back and forth. The problem is that I can sometimes get the rocker to click a second time. For example, a light push on the rocker might read as .1 mm, a little firmer push yields .2 mm. What is the correct method? Should I push as hard as I can on the rocker or accept the first 'stop'? Does any of this make sense to you?

BTW, I am sure that the z block is not moving and that the dial indicator is secure as well.

Thanks!

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E. William Reinecke
1988 Carrera Targa

Treying this for the first time I have made the same observations and will be interested to hear what the procedure is.

William and Bruce,

Did you 'preload' the dial indicator to at least 0.5" 'into' its' travel range before tightening the indicator to the 'Z' bracket?

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Warren Hall
1973 911S Targa

Warren - yes. In fact, the geometry of the distances involved requires that the dial indicator be loaded almost a half an inch before the checking the play. I also replaced the tip of the indicator from a point to a 'foot' so that it would not slip off the adjusting screw or fall into the screw slot.

Willian,

I sounds as if there may be a wear pattern inside the swivel-foot that sometimes 'catches' and sometimes doesn't, and the difference just happens to be 0.1 mm or 0.004"! Did this happen on more than one particular rocker?

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Warren Hall
1973 911S Targa

Yes, it has happened on more than one rocker. But it is funny because it seems to be that the rocker is not resting on the cam properly, not the valve stem. I press the rocker firmly on the valve stem and then rock it towards the cam to measure the gap. It will 'click' and register a bit more gap than at first.

OK, I thought it was happening at the valve end ... it may be due to rocker-arm shaft or bushing wear (maybe a little of both) ... and it sounds as if you will have to do a bit of pushing and wiggling on valve adjustments, though ultimately you probably should take a look at all of the rockers and shafts. Did you see Leland's pictures showing rocker shaft wear as practically the only noticeable wear inside his engine?

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Warren Hall
1973 911S Targa

Yes, I have experienced this. If, in performing this procedure, you both pull and push on the rocker arm, there is some potential for your measurement to include some (about half) the rocker arm play, if there is any. Further, I do not believe this is what you are experiencing. I believe Warren was right the first time in that it suggests a worn swivel foot. By the way, I have wondered whether the swivel foot can be replaced without removing the rocker arm.

Anyway, I have found that if you don't go with the longest measurement, the tappet will make noise. the trick I have found is to make your clearance (0.1mm or whatever it's supposed to be) be the farthest you can get it to travel. If you can get the gauge needle to move farther than spec, it's too loose. At least that's what I've found.

Andras suggested that the dial indicator mathod may avoid inaccurate readings due to the cupped foot that contacts the valve stem. I think this is related. I miss Andras.

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'83 SC

Thanks for the tips. I was adjusting them to the first 'stop'...I guess that explains the racket in the valves. I am going to go back and push them as hard as I can and see what happens...I am sure that the cam presses them harder than I ever could!