if you do have worn rockers with only a groove worn into them, (which would be very likely on an engine that old) you can get a decent adjustment with a feeler gage cut down to slightly narrower than the valve stem. Except for the 4 years or so I had the engine with the rebuilt rockers, I have done it for 30 years now. However they can wear far enough where there is an actual recess in the rocker. At that point they need to be refurbished. Several places do it, I had Larrowe and sons do mine, I was very pleased. But then again being that old you (well, I don't know about YOU personally, I meant your trucks engine) most likely have worn guides as well as any other malady that may strike this area of the engine.
Last edited by brokenhead; 05/03/2013 6:43 AM.
