Timing confusion !

Discussion in 'Mech Tech' started by redgaz, Aug 7, 2019.

  1. Chrisd

    Chrisd Supporter

    I noticed the name!

    Honest guv, I've checked, but it is an old version (1989). I think the last code is GD but I could be wrong
     
    Last edited: Nov 14, 2019
  2. 77 Westy

    77 Westy Supporter

    It doesn’t matter what the code is, your engine isn’t standard. As above, set it to 30deg BTDC at maximum advance with the vacuum port on the carb plugged. Presumably you have a timing scale and know where TDC is?
     
    mcswiggs likes this.
  3. exactly the same engine as mine, was fuel injected, now on ict carbs. i have 123 distributor on mine.

    timing is set as per @redgaz 's point #1, post #1 in this thread: "1) Set at 28-32 degs BTDC max advance, vac hose off and blocked @ 3000 rpm with strobe."
     
  4. Chrisd

    Chrisd Supporter

    77 Westy - thanks and yes I have a strobe and timing scale and TDC

    Rob.e - I was not sure how different the settings might be so I thought I'd check. But having this information really helps.

    Cheers
     
    rob.e likes this.
  5. ^this. Plug the vac hose on the carb. Timing at idld will likely end up at about 10*, but it’s irrelevant.
     
  6. redgaz

    redgaz Supporter

    One of my main problems with setting ignition timing on my AE 1600 tp engine was assuming that the one and only 'V' groove in the innermost side of the crank pulley was TDC, it's not, it's 5 ATDC, so for ages i was setting the timing 5 degrees out.
    In 1970 with all the Californian emissions stuff intact ,DVDA dizzy etc which it hasn't had on for a long time, one would set it at idle to that mark (5 ATDC) and back then that was probably ok.
     
    mikedjames likes this.
  7. mikedjames

    mikedjames Supporter

    Distributor codes, timing pulleys, timing characteristics. From 1972. 20191114_205005.jpg
     
    Valveandy likes this.
  8. PIE

    PIE

    You havnt been pumping your accelerator without the engine running by chance have you, that will make fuel drip from the bushes, the accelerator pump will dump on the shaft and without the vacuum it will leak.
     
  9. mikedjames

    mikedjames Supporter

    Its a weakness of all the carburettors they see fit to put on aircooled VWs is they have steel in aluminium alloy throttle spindle bearings.

    The throttle body I have which I think is off a Mk2 Golf GTI has needle roller bearings... so they dont wear and leak...but they arent washed with petrol either, as that goes in from the injectors just above the inlet valves..

    Carburettors with roller bearings also need seals on the spindles...
     
  10. Unless you’ve got Dellortos ;)...
     
    Dubs likes this.
  11. ...or the big Webers, I believe...
     
  12. I agree with the "set the maximum advance to 28 - 32 BTDC with vacuum disconnected".
    This all depends of course, on where TDC is on your particular engine! :thinking:

    Resurrected from an old post of mine elsewhere -

    VW produced pulleys with a large variety of timing marks for different engines, and for different local emission/fuel quality requirements.

    It follows that a 40 year old engine may not have the correct pulley, probably having been rebuilt more than once. Never trust pulley marks on a new-to-you engine.

    Find and mark the TRUE TDC. Ignore the "pencil-through-the-plughole" method, it's inaccurate.

    Mash out the insides of a spark plug and insert a length of threaded rod through it secured by a nut on either side. Adjust this so that about 10mm protrudes further into the cylinder than a spark plug would.

    Insert this into the plug hole and turn the engine by hand until the piston jams against the rod. Draw a temporary mark on the pulley where it lines up with the crankcase centre. Turn the engine the other way until the piston again jams against the rod and again mark the pulley.

    True TDC lies EXACTLY halfway between the 2 marks. I've filed a large new notch on my pulley and scratched "TDC" on it for future reference.

    You now have a true TDC you can rely on for the life of the engine. :thumbsup:

    -----------------
    To time for a vacuum advance distributor….

    Get the engine running and warm at whatever timing works.

    Disconnect and plug the vacuum tube.

    Set the timing so that maximum advance when revved hard is 28 degrees BTDC. No need to make a second timing mark. I’ve treated myself to an adjustable strobe light for £30 – just dial up 28 degrees and turn the distributor until your new TRUE TDC mark lines up with the crankcase centre.

    Should run like a dream now, mine does :thumbsup:
     
    Last edited: Jan 11, 2020
    Iain McAvoy, Chrisd, Davipon and 2 others like this.
  13. Chrisd

    Chrisd Supporter

    Hi all. A puzzle for you.

    I have checked timing on my bay. Timing mark found (see picture) and vacuum plugged. The bus was running generally OK yesterday but with some juddering at 30mph.

    So today I checked the timing and it was way out. At least 15degrees. So I've pulled the distributor round, quite a way and now (timmed at 30 at 3000rpm ) she is backfiring and spitting.

    Any ideas other than to sack the numpty who is fettling.

    I was wondering if I have marked the correct timing mark between the two white marks?

    Thanks
     

    Attached Files:

  14. 77 Westy

    77 Westy Supporter

    Are you sure they’re timing marks and not the indentations from the pulley balance weight? The timing groove is on the backside of the pulley, you can feel it but it’s not easy to see. As you don’t have a timing scale, what are you using as deg. advance/retard? And how/where have you marked TDC?
     
    snotty likes this.
  15. Chrisd

    Chrisd Supporter

    I agree it took a long time to find the mark. I painted the two on the front to indicate where the mark is on the back of the pulley. You can just see the tiny mark, grey colour notch in the closed up photo.

    The timing scale is on the other side. You can see it in the top left corner of the photo.
     
    77 Westy likes this.
  16. 77 Westy

    77 Westy Supporter

    Sorry, I spotted the timing scale just after I posted, then the computer crashed and I couldn’t edit… Why have you marked two points on the pulley? I guess you know which one to use. For the timing to move 15 deg. maybe the distributor has seized, have you checked that the vacuum and mechanical advance moves freely?
     
    Last edited: Jan 4, 2020
    Chrisd likes this.
  17. Chrisd

    Chrisd Supporter

    Thanks for he reply. I painted two spots as an old mechanic once mentioned that it is easier to spot the dark space between the two ...does not really make a difference as I'm looking at the timing spot itself when I'm checking.

    So latest observation is that if I set the timing to be 30degrees at 3000 rpm and then let the rpm back to idle, the timing at idle is high (about 15 or 20).

    I will read up about the suggestions on vacuum advance etc as I'm not sure what to do there.
     
  18. 77 Westy

    77 Westy Supporter

    It’s possible the advance mechanism is sticky – the bit that moves with the bob weights and springs as the revs increase. You can check that the vacuum advance moves by sucking (hard) on the hose to the can while looking at the points plate inside the distributor. Red arrow:

    distributor exploded drawing.jpg
     
    Chrisd likes this.
  19. Chrisd

    Chrisd Supporter

    77Westy you are a star!
     
  20. @77Westy that's a great picture of the distributor, where is it from?
    A
     

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