The .013" valve clearance is a "cold" setting isn't it? So after the pushrods and valve stems heat up and expand, doesn't that value reduce toward zero?
If so, then having an initial .001" intake cam lift occur at 31 degrees (as Doug supposed) could make sense. The mechanical "slack" would mostly be gone in a "warm" engine.
Or do I need to change to different hallucinogen?
Great discussion - as always.
Hey Doug - you haven't "un-spammed" my email status yet! - lol
Jim M
--Previous Message--
: It sounds like the discrepancies and
: variations could be in the setup for
: picking up the measurement off the
: lobes, going by the lobe center you are
: fine.
: Glad it worked out!
: Glen
:
: --Previous Message--
: Glen, I looked at the angles when the
: cam
: showed the 0.013" lift off the
: base circle as mentioned yesterday. I
: repeated the test a few times and got
: different values but all close to each
: other with a similar spread around the
: LCA. For example, in one test that I
: remember 0.013" lift on opening
: came up as 22 BTDC, on closing 59 ABDC.
: That's 22 + 180 + 59 = 261. (261 / 2
: ) - 22 = 108.5
:
: Likewise, if I found the approximate
: "max lift" point on the cam
: intake lobe, set the indicator to
: "zero" and took angle
: readings 0.005" each side of max
: lift, the average came in at 108.5
: again.
:
: So I had one set of measurements based
: on the start of lift and one set of
: measurement based each side of max
: lift. Both tests consistently came up
: with an LCA of 108.5 and I am happy
: with that.
:
: I did not make these tests on the
: exhaust lobe.
:
: I don't pretend to know the specs of
: the S2 cam beyond being told the LCA
: was 110 and the opening/closing angles
: are supposed to be 31/71 with a
: duration of 282. I cannot tell you why
: 0.013" of lift didn't occur at 31
: BTDC. Maybe 31/71 occur closer to
: 0.001" of lift. I'm not sure it
: matters if the max lift on the intake
: lobe happens when it is supposed to.
:
: Regardless, I greatly appreciate your
: help with this. I was in a total state
: of confusion regarding the cam sprocket
: position prior to your posts.
:
: Regards,
: Doug L.
:
:
: --Previous Message--
: That's a good number but I'm curious
: why
: the opening/closing points didn't come
: in right?
: To my knowledge that is a symmetrical
: grind.
: Maybe you should check with Ted to be
: sure.
: What are opening/closing points?
: Glen
:
: --Previous Message--
: Success !
:
: I tried a few different orientations of
: the 2 bolt holes on the cam sprocket
: and ended up where I started. I was
: not able to get opening to start at 31
: BTDC and end 71 ABDC with 0.013"
: of lift. However, when I used the
: 0.005" before and after max lift
: and averaged those angles... I came up
: with 108.5 degrees. Then I took the
: degree values at 0.013" of cam
: lift (before and after) and applied
: Glen's formula and again came up with
: 108.5 degrees. That tells me that I
: have found the max lift and set it at
: an acceptable position.
:
: I understand that a few degrees of
: advance may improve low end torque...
: more importantly, when the chain
: stretches, I should end up close to the
: 110 ATDC spec.
:
: Thanks to all for the help. I feel
: much better now.
:
: Doug L.
:
:
: Doug L.
:
:
: --Previous Message--
: "The indicator extension sits
: inside
: the bottom of that lifter."
:
: OK but inside the tappet is concave, so
: ANY misalignment will reflect in the
: readings to some degree.
: If the numbers don't come out right
: when you check it or you don't get
: repeatability, this is where you might
: first look as a cause.
: Try it and see what you get.
: Glad it's making some sense!
: Glen
:
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