[TR] adjusting valves hot

Randall tr3driver at ca.rr.com
Thu Sep 17 22:08:44 MDT 2009


> M'self, I think this practice persists from the early days of 
> hot rods 
> and hydraulic lifters.  Then, it was fairly common to see V-8 owners 
> cutting a big slot in a spare valve cover to minimize oil 
> splash while 
> adjusting lash when hot.  I suspect this was necessary because cam 
> grinding wasn't quite as precise as it is today, nor was the 
> manufacture 
> of the lifters, so the lashes necessary varied.

I believe there was another reason.  Hydraulic lifters have a tendency to
'pump up' and hold the valves open if the engine is run at a high enough rpm
to cause valve float.  A common workaround "back when" was to adjust for
zero lash (or just a little bit of lash) with the lifter fully extended.
But they would not reliably extend without the engine running, so the easy
solution was to do it with the engine running.

I'd have to go dig out the manuals to be certain, but ISTR that the book
valve adjustment procedure for my 65 Oldsmobile V8 was to back off the
adjustment until the valve lash was audible; and then turn the nut a certain
number of turns.  The idea being to center the hydraulic lifter in it's
range.  There were even special clips available to go over the oil holes in
the rockers, to reduce the amount of oil thrown around.

Randall


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