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Ignition TimingMy mechanic will adjust my carburettors next week, and he ask me for the ignition timing-data. He tryed with the neon-lamp, spotted on the fly-wheel, and he read 13 degr., he said. He do have no data-sheet for the car (I think only 2 XK 120 where sold new in Norway) I told him could contact the XK-lovers-group. I should appreciate if someone could give me the data a mechanic need to do a proper job adjusting the ignition. - Martin Jacobsen Set the contact breaker points to .012" and the sparking plugs to .022". Turn the engine clockwise from the front until the #6 (front) piston is on the compression stroke and 5 degrees (approx. 2 flywheel teeth) before top dead center. Set the distributor micrometer adjustment to the centre of the scale. Attach a voltmeter or 12v light between the distributor connection and ground, and turn on the ignition. Rotate the distributor until the light just comes on. Clamp the distributor. Then take the car out and drive it. If it pings accelerating up a hill, retard it using the micrometer adjustment and test again. - Mike Eck '51 XK120 OTS '62 3.8 MKII From memory, I believe 10 to 12 degrees before top dead center (BTDC) will be fine! The neon lamp approach is the preferred classic method - always works! This should be done with the vacuum advance disconnected and plugged, with the endine running at idle. Could be done with the vacuum line connected, but this way we remove another variable! - Larry Schear Twin Cam, Inc. On my car, eng. # NC8338-9, the factory SUPPLEMENT TO MK VII/XK120 SERVICE MANUAL for MK IX called out 4 degrees for all Mk IXs -- but my AUTOBOOKS 702, XK120, 140, 150 MK 7, 8, 9 by Kenneth Ball (published 1973) gives far more detailed info for all models. For my Mk IX, distributor # 40665.A (which I have) and 9:1 head, timing is 5 degrees BTDC. On mine, timing marks are set into front crankshaft damper (with pointer to set bolted in above sump); scale is: 10/////////0 (lines are vertical). So I set the pointer at the center line (5), timed it statically (with light hooked up to distributor and points so it flashed when they opened), and dynamically (with white chalk mark at center line ,5, stroboscopic timing light hooked up to #6 cylinder, vacuum advance disconnected, and distributor clamp loosened to turn it); set at 500 RPM (normal idle) and 1,000 RPM as a check. No high-RPM/total advance test done (may do later), but spot on after all this; runs perfectly, to 5,000 RPM -- no pings or other problems -- just runs correctly! Bruce tells me there are MANY variables re: timing -- MANY different distributors were used, etc. My Kenneth Ball book calls out distributor #s, timing for ALL models of XK120/140/150/VII/VIIM/IX; if anyone needs this info, let me know at <jagmkix@cwo.com>. - Larry Martz
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