Lotus Elan

Uprated Ignition Coils

PostPost by: type26owner » Fri Aug 13, 2004 2:58 am

Hey Rick,
The trick is make the very best of the present situation. The Lucas dizzy requires regular maintenance and if this is done on a yearly basis it will perform very well. There's five areas to check assuming you've already replaced the problematic points with a hall effect or photo diode switch. If you've have not done this already then by all means do so soon. First, the timing scatter is affected by the vertical axial play of the mainshaft. The play should be between .000-.002" and normally shimed between the drive gear and the dizzy body. Anymore and the power output of the engine is deminishing. Two, the mechanical advance centrifical weights need lubing with a light white grease like LubriPlate on the pivot pins and their rubbing pads. Do not let them develop fretting rust! Three, the mechanical advance springs are subject to rapid fatigue. Replace or adjust them to maintain the proper advance curve. Four, inspect the mainshaft drive gear for any wear or looseness. This means checking the mating jackshaft in the engine for gear wear and any movement along it's rotation axis also. Five, adjust the tension to the manual specs for the camshaft drive chain. I can always tell when the maintenance needs to be done again when it starts to backfire on overrun. It does this as an occasional loud sharp pop. I suspect this is mainly due to the stiction of the advance weights from lacking enough lubrication and it introduces more and more hystersis into the advance curve.

I've found the twincam is extremely sensitive to small timing errors. The problem is it only delivers maximum performance in a very small bandwidth of a few degrees but it will still runs with an underwhelming lackluster in a huge timing bandwidth. Even the 104 hp rated engine should gently stretch your neck muscles when it comes on the cams at 4k rpms when it's tuned correctly.
Regards,
-Keith
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PostPost by: steveww » Fri Aug 13, 2004 9:36 am

Timing scatter comes from slap between the drive and jackshaft also the drive may become loose on the dizzy shaft. Reconditioned units are available from a couple of suppliers and Mallory do a new unit that will fit. The old dizzy of my twinc had about 6 degrees of scatter and whilst the engine ran OK it was a significant improvement when I installed a recon unit :D

I agree with Keith that lubrication is essential. I put a few drops of engine oil down there every time I do a general check of fluids etc.

Of course if you are not too worried about originality then you might want to try <a href='http://www.bgsoflex.com/mjl/mjl_edis.html' target='_blank'>http://www.bgsoflex.com/mjl/mjl_edis.html</a> or the more exspensive options from DTA, Emerald etc.
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PostPost by: type26owner » Fri Aug 13, 2004 3:01 pm

One last little minor point everyone should be made aware of. The dizzy rotors have been changed in size in the last couple of years. They are now taller by about 1mm. This is no problem unless you've also got a rotor from a hall effect or photo diode which needs to be installed underneath it. The extra thickness of the switch's rotor can cause the dizzy rotor to sit too high and it could rub on the plastic boss which houses the carbon contact feature of the cap. If this happens the dizzy rotor will short out within a few hours. Bummer time. :( But preventable.
-Keith
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