like 3-4 thousandths loose, engine runs smoother, and has
a nice cam tappet sound, more torque.
The fact that it has more torque is one good reason to buckle down
and do it. It has to do with the “quieting ramps” that are built
into the cam profiles. Basically, the cam profile tries to gradually
close up the valve lash BEFORE it starts the actual valve opening.
As a result, clearances on the low side tend to cause the valves to
open – just a hair – long before they’re supposed to, and stay open
– just a hair – long after they’re supposed to have closed.
Besides causing a considerable reduction in low-end torque, this
can’t be good for valve life.
Those same quieting ramps also can cause confusion when measuring the
clearances. You’ve gotta be very sure to be all the way around on
the heel of each cam lobe. If you try to measure anywhere near the
actual lobe, you may actually be on a quieting ramp and get smaller
clearance measurements than you should.
Also remember that running clearances aren’t the same as cold
clearances, which are what you can measure. The whole point of the
clearance spec is that it won’t totally close up under any condition,
including shortly after startup when the valves themselves are hot
but the head is still cold.
I dunno if 3-4 thou is the best advice. IIRC, it was different on
exhaust than on intake. The exhaust should be 3-4 larger than spec,
the intake should be right around the wide end of spec, .012" I
Doing this job involves removing the cams, which in turn involves
fiddling with the timing chain tensioner. Be sure you understand
what’s involved there. I think most of us who have done this job
would recommend NOT trying to fully retract the tensioner to its
latch. Rather, just go ahead and take the sprockets off and set them
on their supports, adjust the valves, and then “trip” the latch on
the tensioner while putting the sprockets back in place.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !On 23 Apr 2014 at 6:32, Ronbros wrote: