1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Dwell angle or points gap?

Discussion in 'Bay Tech Clinic' started by Ian and Shelley, Oct 16, 2019.

  1. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    294
    Location:
    Umina Beach
    Hello...

    A few more questions...

    When setting points at 18 thou ( as recommended in many manuals I get a dwell angle of 35 ish
    If I drop gap to about 12 thou I get 46 dwell angle..

    I believe we aim for dwell of 45-50

    Should I assume I am poorly setting points with feeler gauge and accept dwell angle as correct? Or other reasons for errors?

    Also, clarification of my thinking please .....
    When setting the points and locating the high point of dizzy cam, should this high point alsoalsobe be showing TDC. I.e..zero degrees on timing scale or about 8 degree BTDC?
    Or are dizzy cam and position of timing scale not relevant

    Thanks as always..
     
  2. cbus

    cbus Well-Known Member

    Messages:
    12,721
    Location:
    sunshine coast
    Highest point on cam is when you set points gap.

    Trust dwell rather than manual setting with feeler gauges.

    50 is setting for new points.
    Old points accept 42-58.
    Anything between that is fine.

    Additional info...
    Set gap to widest of choices ,is about 45-50dwell
    This allows for wear which closes gap and retards timing.

    Many points inferior rubbing block now and wear quickly.
    Especially in first 500km
    Check dwell or timing after a few days and at 2.5k km just in case.
    If it starts to run rough at low revs and poor idle a few 100 km after fitting new points it's usualy due to rubbing block wear and hence retarding timing.
     
    Last edited: Oct 16, 2019
    Mordred, Wayne murray and grumble like this.
  3. tillis

    tillis Well-Known Member

    Messages:
    297
    Location:
    gold coast
    Yep recently checked points in my 82 T3...had to grind them flat and set them by eye a bit much obviously...a bit advanced and hesitates starting but then it flies!
     
  4. David H

    David H Well-Known Member

    Messages:
    6,017
    Location:
    newcastle
    That be 'old school'! Love it.
    Cheers
     
    Last edited: Oct 17, 2019
  5. Kai

    Kai Well-Known Member

    Messages:
    4,768
    Location:
    Sydney, NSW
    Make sure the two contact faces are square with each other. A lot are not out of the box and will give you a skewed result. just requires a small amount of bending.
     
    Barry likes this.
  6. T1 Terry

    T1 Terry Well-Known Member

    Messages:
    1,426
    Location:
    Mannum South Australia
    On the road I got to the point of making sure the points closed as the dissy turned and then set the timing static. The wider the points gap the less time the coil has to reach saturation so when the points open and the magnetic field in the coil windings collapses, the spark to the plugs is reduced .... but .... the wider the gap the more time the coil has to dissipate the oscillations in the primary windings (surge backwards and forwards) and the more time the condenser (capacitor) has to charge so the points close is clean with no arc back across the contacts so the contacts stay clean and not pitted a lot longer.
    The relay feeding full battery voltage to the coil really helped with the coil saturation so I never experienced any down side to the wider than normal gap, just had to make sure the points closed and opened on every lobe, particularly no.3 cyl because the timing is slightly off set on that cyl to assist cooling.

    T1 Terry
     
    David H likes this.
  7. David H

    David H Well-Known Member

    Messages:
    6,017
    Location:
    newcastle
    Hi Terry,
    Could you explain more how this happens please? I'm Shultz;). Know very little. I'm still processing the coil comments!
    Cheers
     
  8. Barry

    Barry Well-Known Member

    Messages:
    4,782
    Location:
    Abbotsford NSW
    @T1 Terry

    Wasn’t the retard(?) of #3 only on early non dog house / oil cooler type 1 motors?

    The oil cooler in the non dog house blocked the air flow and made #3 run hot
     
  9. T1 Terry

    T1 Terry Well-Known Member

    Messages:
    1,426
    Location:
    Mannum South Australia
    Watching the primary pattern on an oscilloscope showed the points based ignition engines all the way through the air cooled motor range still had that offset on no.3 cyl compared to the others. Any that had an after market electronic trigger conversion that did away with the points would show the primary patterns perfectly matched one on top of the other. In any other vehicle it was a red flag the distributor bushes were worn and it would show a curve across the spread patterns at the points close position, but the VW would have 3 points close identical and no3 separate.
    A real catch for anyone who didn't know about it and put the plug wires in the distributor cap with no1 180* out from where it should be, not long after no3 would drop an exhaust valve on a long hill climb, generally heading up either Mt Ousley or Bulli Pass, I lived in the Illawarra back then and had a mechanical workshop in Wollongong called ACEIS Automotive.

    T1 Terry
     
    oldman and David H like this.
  10. Mr Beckstar

    Mr Beckstar Well-Known Member

    Messages:
    1,116
    Location:
    Bateau Bay, NSW
    And that’s what caused my breakdowns at Mallacoota! :mad:
     
    Mordred likes this.
  11. Mr Beckstar

    Mr Beckstar Well-Known Member

    Messages:
    1,116
    Location:
    Bateau Bay, NSW
    The cam that opens the points is ground to a shape that gives number 3 cylinder a little less advance. There are four lobes on that cam, one lobe for each cylinder. VW did that as they knew that cylinder would run hotter then the others because of the oil cooler location.
     
    David H likes this.
  12. T1 Terry

    T1 Terry Well-Known Member

    Messages:
    1,426
    Location:
    Mannum South Australia
    Never be tempted to file the spike off one side of the points or to file the contacts flat. You could do this back in the very old days because the contacts were actually all white metal, not just a white metal coating. Back when the contacts were pure white me.tal, you could actually unbolt the contact piece from the base or arm and replace it, the same with the spring and the rubbing block. Now all points contacts are "ventilated" in other words, a hole in the centre so there is even less area to coat with the precious white metal.
    This does make the dwell angle the better choice for resetting a used points set, but I've been resetting the Kombi's points by eye on the side of the road for that long now I couldn't be fussed to go and find a dwell meter :lol:

    T1 Terry
     
    TeeBee, Grantus, oldman and 1 other person like this.
  13. 1500king

    1500king Well-Known Member

    Messages:
    1,563
    Location:
    Adelaide, SA
    0.015" point gap. Stick to vw spec on dwell, 45-55 degrees.
     
  14. 1500king

    1500king Well-Known Member

    Messages:
    1,563
    Location:
    Adelaide, SA
    If you can't achieve it, then distributor is probably needing some love.
     

Share This Page