murrayarnold Posted August 31, 2020 Report Share Posted August 31, 2020 Good day all. Does anyone know how much advance/retard that the small wheel puts on the timing. How many revolutions relates to one degree for example. Thanks Quote Link to post Share on other sites
RobH Posted August 31, 2020 Report Share Posted August 31, 2020 (edited) If it is a Lucas original then I believe 11 clicks of the serrated wheel equals 1 degree. The modern replica distributors may have a different number of serrations on the wheel and a different thread on the shaft, so that probably won't be right for them. There should be a series of graduations visible on top of the vacuum unit behind the diaphragm housing. Those are 4 degrees each. Edited August 31, 2020 by RobH Quote Link to post Share on other sites
Peter Cobbold Posted August 31, 2020 Report Share Posted August 31, 2020 1 hour ago, RobH said: If it is a Lucas original then I believe 11 clicks of the serrated wheel equals 1 degree. The modern replica distributors may have a different number of serrations on the wheel and a different thread on the shaft, so that probably won't be right for them. There should be a series of graduations visible on top of the vacuum unit behind the diaphragm housing. Those are 4 degrees each. The disy specs usually refer to disy degrees, so crank degrees are double. Quote Link to post Share on other sites
RobH Posted August 31, 2020 Report Share Posted August 31, 2020 (edited) The info I was quoting says those are crank degrees Peter. Edited August 31, 2020 by RobH Quote Link to post Share on other sites
ed_h Posted August 31, 2020 Report Share Posted August 31, 2020 I calculated rather than measured this, and came up with something closer to 20 clicks per degree. I think the fineness of the serrations on the wheel may be differentbthan Rob's. My logic is here, at the bottom of the update at the bottom of the page: http://bullfire.net/TR6/TR6-11/TR6-11.html Quote Link to post Share on other sites
Peter Cobbold Posted August 31, 2020 Report Share Posted August 31, 2020 8 minutes ago, RobH said: The info I was quoting says those are crank degrees Peter. OK Rob. In the past Ive been caught out by the bible and this page, until I spotted the small print in blue: http://www.teglerizer.com/mgstuff/advance_curves.htm Peter Quote Link to post Share on other sites
RobH Posted August 31, 2020 Report Share Posted August 31, 2020 (edited) 40 minutes ago, ed_h said: I think the fineness of the serrations on the wheel may be different than Rob's. Yes I wonder whether there was much consistency in the serrations over time. I doubt the clicks were supposed to be the calibration - that was why there were graduations provided on the shaft. Edit: I've just been out and measured a DM2. It's difficult to tell exactly because the graduations are quite wide but as best as I can tell there are 42-45 clicks per graduation division of 4 degrees. That makes near as dammit 11 clicks per degree, at least for that particular dizzy. Edited August 31, 2020 by RobH Quote Link to post Share on other sites
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