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<DIV><FONT size=2>As said elsewhere TDC and BDC are not relevant, if you are
referring to the piston. If you look at the valve timing the inlet lobe is
at its peak 70-odd degrees before BDC, and the exhaust valve is at it's peak
about the same distance after BDC. So the back of the lobes are under the
followers 180 degrees from there, which is more than 70 degrees before TDC and
after TDC respectively.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>But it shouldn't make a difference, look at the cam profile,
and the base circle should extend for significantly more than half way round the
cam, in theory giving more than 180 of engine rotation where the clearance
should be the same.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV>
<DIV><FONT size=2>Note in theory, which is why I said it's one of the reasons
why I find the position of greatest gap to adjust them, which on mine (and
others I have done) can be several degrees either side of the strict RON
point. </FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Also, whilst the dynamic forces on the piston etc. are
slightly different on compression and expansion etc, statically TDC is
directly above BDC, how could it be anything else?</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>PaulH.</FONT></DIV></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2> </FONT>----- Original Message ----- </DIV>
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<P class=MsoNormal><SPAN style="COLOR: #1f497d">Regarding Rule of Nine, I
understand having 8 all the way up to set 1. But there is a significant
rotation between “real close to the top” in front of, and after TDC. This can
be seen with rotation the engine and seeing very little to no movement. Also,
if I am not mistaken 8 TDC is not perfectly in line with BDC of 1; there is a
bias. This means that when 8 is TDC, 1 is not absolutely BDC ready for
measurement. So the question is, how do you ensure, with all of that slop,
that you truly have BDC?<o:p></o:p></SPAN></P></DIV></BLOCKQUOTE></BODY></HTML>