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Ignition timing scatter

Discussion in 'Rover P6 Engine 4 cylinder' started by Demetris, Oct 10, 2018.

  1. Demetris

    Demetris Well-Known Member

    The last time that i went for a ride with my TC, it felt somewhat lazy so i thought i d' better have a look at the ignition timing. Timing light on the flywheel and it was obvious that at idle, the timing varied at what looked like 3 or more degrees. Taking the average of that, it seemed indeed to be around the TDC, so i turned the distributor a little in order to bring it back up to the required 6 degrees BTDC. Now the car drives better, but i wonder about the timing scatter at idle (at speed it looks to be rather stable). The timing chains must be well worn now, at around 110K miles, and at least the top one feels somewhat slack on finger pressure.
    So, do i have to blame the timing chains only, or could wear in the distributor cause this problem?
    The distributor is a standard Lucas 25D4, with Lumenition magnetronic fitted.
     
  2. harveyp6

    harveyp6 Well-Known Member

    It could be either or both. Probably the best thing to check first is the distributor, purely because it's the easier option.
     
  3. sdibbers

    sdibbers Well-Known Member

    My guess would be the springs under the distributor baseplate. I had my dissy rebuilt and recurved a few years ago. Before then it was always all over the place timing wise. It got so bad the ignition would go to full advance above 1500rpm
     
  4. classicalgreen

    classicalgreen Active Member

    I changed my dizzy for a full electronic version at NEC visit. though rev counter seems to be. fluttering or wondering when idling, everything else seems fine. unsure state of chains and timing gears but until I get other issues or high mileage ( current showing 38K and thought to be correct despite. 6 owners as spent life in London ergo high traffic and little used ) at later date.
     
  5. sdibbers

    sdibbers Well-Known Member

    I've always wondered what sort of advance curve those off the shelf electronic dissys have? I wonder if they are best for our four cylinder cars.
     
  6. sdibbers

    sdibbers Well-Known Member

    @Demetris Maybe take off the oil filler cap and see how much slack the top chain has. Are you hearing any timing chain rattle at start up?
     
  7. Demetris

    Demetris Well-Known Member

    OK, thanks to all of you for your advice. As i happen to have a new old stock 2200 TC (complete with the famous rev limiter rotor arm) on the shelf, i think that i will just swap it (minus the rotor arm). I presume it won't be exactly what my engine needs, but it won't too far away, and my engine has already the carbs of the 2200 TC.

    Steven, the top chain doesn't feel too bad, and there are no nasty rattles either, so i am not rushing to replace the chains, especially as i drive it so little these days. Perhaps one day i will remove the sump to replace the bearings, so i could do the chains, tensioners and oil pump gears in one go. Not that any of these feels bad now, but as i already have through the years gathered almost all the required parts, just for the satisfaction that i will have again an almost new engine.
     
  8. PNP

    PNP Member

    I currently have the distributor for my SC Auto away getting checked out and regraphed. It has an accuspark electronic ignition that I installed a little while back that tey say is working fine.
    Although I have got it back yet (next week) they indicated that the main problems were (in order) 1. the rotor button, 2. tired springs & 3. the age of my leads (they ask you to send it with the distributor).
    The service they offer includes checking the curve and tweeking it for modern fuel. Its costing around AU$250 (150 Euro) including a new set of leads.
    Rebushing the shaft or playing with weights would have been extra.

    Scientifically, I'm hoping its a good investment.

    Note, I'm also redoing the valve clearances before I put her back on the road I won't be able to report back for a few weeks
     
  9. classicalgreen

    classicalgreen Active Member

    I was told advance curve is set up for each car version they supply .it are complete with auto advance vacuum unit fitted , so not the type with 'programmable' advance which would be better still. ( and cost ££ ) as for performance ..it hasn't made any difference acceleration but does start and run better especially when warm. have a gut feeling initial advance can be set higher than the 6 degree recommended but aware there are many saying actual TDC mark isn't. accurate on some engines . will check that out next season when I het chance.
     
  10. sdibbers

    sdibbers Well-Known Member

    Which supplier are you using for this? most seem to sell the same unit no matter the application.
     
  11. classicalgreen

    classicalgreen Active Member

    if I recall correctly was "power spark". I bought it few years back at my yearly. trip to NEC show in November. was a full unit with dizzy cap minus HT Leads. ( already replaced) came with a high energy coil as part of kit. slight re-wiring needed on dizzy but instructions came with unit. ending up using one less wire if I recall(white trace?)
     

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