This is the reason valve lash on old engines is difficult to adjust, the rocker on the left has a wear depression of about .010.  Normal feeler gauges will bridge this depression and prevent accurate adjustment.  The rocker on the right has been ground by hand with an angle grinder and 80 grit wheel. This engine ran well for several more years before replacement.

Doug T

The Highlands, Louisville, Ky.

Ted, that topic was a nice one. When i adjustet my valves i sett it to 0,020 cold, to be shure the hot clearence would be enough. But i see it would have worked out with 0,019 cold as well.

Robin Norway

Here’s a link to a past thread discussing several different methods for adjusting the valves.  The quarter turn method is about as simple as they come though.

http://www.y-blocksforever.com/forums/Topic8614-3-1.aspx

Lorena, Texas (South of Waco)

1/4 turn.

The thread pitch is 20tpi, so that is .050" per thread (1/20). 1/4 of that is .0125, multiply by the rocker ratio, 1.54 and you get .0193" For low ratio rockers it comes to .0179"


Lawrenceville, GA

I used the 1/4 turn, it worked great. Thanks you all for the advise.

Robin Norway

i looked at the 1/2 turn mentioned and thought it was incorrect.It is 1/4 turn.The theory is based on the pitch of the thread.How far the screw moves as you turn it.

  

Its a quarter turn Rob - and it works like a charm.

 
 Steve Metzger       Tucson, Arizona

Im with Doug T on this one. Is it half a turn or quater of a turn ..Can't remember?



"Came too close to dying to stop living now!"

The problem you are encountering is probably caused by wear on the rocker arm pad that contacts the valve stem.  The valve stem is proan to wear a groove in the rocker that can be several thou deep.  When this happens the feeler gauge bridges the groove and you end up adjusting to the unworn surface of the rocker arm.  Take the rocker arm shafts off the engine and you will see the groove that I mention.  

If you don't want to do that you can probably get close to the proper lash even with worn rockers in the following manner.

Briing #1 to TDC with both valves closed (compression stroke).  Grasp the pushrod with your fingers and twirl it round as you tighten the adjuster.  When it just stops twirling you have established zero clearance within the groove to the valve stem.  Back off the  adjuster 1/2 turn to get the nearly the proper lash, tighten the lock nut if you have one. Repeat this step for the other valve of #1.  Crank the engine 1/4 turn and proceed to do the same thing with #5 and so on through the firing order.  I like to do this with the engine warm but not hot,  in actual point of fact hot or cold will not make enough difference to bother with if the rockers are this worn.

Doug T

The Highlands, Louisville, Ky.

I adjust mine cold by using the firing order.Once you find TDC on compression on # 1 adjust in order 15486372 by turning motor 1/4 turn in direction of regular engine rotation.