>
> I've noticed when setting lash on two separate spit 1500 engines that
> the two open valves don't reach full open at exactly the same crank rotation.
> Which I why I set the valves by the workshop manual chart. Does anyone
> know why this is? Cams in both engines are stock.
The two valves that are open are one intake, and one exhaust. The piston with
the intake open is on the way down, and the one with the exhaust is coming up.
On a 1500, the cam lobe center line is supposed to be at 110 degrees, after
for intake, before for exhaust. So, if you set the engine with one cylinder
at 110 after, the other one, moving the other direction, will be at 70 before.
In other words, theres about 40 degrees difference between the two
centerlines.
I neglected to say yesterday that the exact position of the engine does not
matter for this technic. Just so long as you have two valves mostly open,
you can adjust the two opposite valves.
>
> The difference in lash by either method is very small...at most half a thou.
> The workshop manual method is more accurate.
>
The method I describe *is* the workshop manual method for the engine in
question (BMC A series). Some companies suggested a method of setting the
engine directly on TDC and adjusting four at once. This suggestion strikes
me as not very sound. Doing it this way, none of the valves will be directly
one the back of the heel, and two of them will be real close to the leading
or trailing ramp. A little bit of wear in the cam, and you'll be out of
the ball park.
What evidence do you have that this later method is more accurate?
> timd@ptltd.com (Tim Dziechowski - Phoenix Technologies - Cambridge, Mass)
>
Randy
randy@taylor.wyvern.com
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