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Points / timing

Discussion in '"Stock" Alpine' started by Acollin, May 9, 2022.

  1. Acollin

    Acollin Platinum Level Sponsor

    This stuff only make sense to me on a primitive level. I know how to read the meters and make adjustments , but what they actually do
    /mean separately and together is a bit magical to me.

    I have been tinkering around my 66 series V ( mostly stock) and started wondering a bit. Currently my spark plug gap is .013 and my dwell angle is about 56 degrees. I know that .015 is where my point gap is supposed to be and 60 degrees is what my dwell angle is supposed to be. I know these numbers should be dialed in before one times the car about 8 degrees btdc.

    My current questions are:
    1) if I widen my points to .015 and change my dwell angle to 60 degrees, how much of an effect will I see/ feel?
    2) by changing this numbers a little over or under what the spec sheets want, how will my car respond?

    3) are there safe parameters ex: how low or how high can these numbers go before one does damage or the car will run poorly or not at all?
    Thanks for schooling me . tons more to learn.
  2. husky drvr

    husky drvr Platinum Level Sponsor


    The Alpine distributor has a points cam profile for increased dwell timing for "better" high RPM performance. Also, dwell isn't really independently adjustable from the points gap. The dwell timing, points gap, and distributor cam profile working together control dwell.

    As the point gap widens, the dwell time decreases. WSM 145 states dwell should be 60* +/- 3*. You're in the ballpark. If you widen the points gap, you'll loose a bit of dwell. It should not make any real difference unless you always drive your Alpine at 10/10ths. Most four cylinder engines run a dwell timing of about 45*. I'll guess that your seeing the effect of a bit of wear on your points cam. It should never be an issue unless you are racing.

    Here is an article that explains the answers to your questions better than I can (scroll to the top to see entire article):

    https://www.liveabout.com/dwell-and-timing-explained-even-more-4059400#:~:text=The dwell is adjusted by setting the points,field collapse before it delivers all its energy.

    Hope this helps,
    puff4 likes this.
  3. Acollin

    Acollin Platinum Level Sponsor

    Thanks for the article

    If the wsm says 60 degrees, why do you say most 4cyl engines run a 45 degees?

    Also: I was reading over the “static timing” procedure in the wsm and had a question. If one undoes the connection between the coil and the LT/ distributer to attach a 12 volt bulb, where does the electrical current come from to power up the light bulb?

    Thanks in advance of your answers!!
  4. husky drvr

    husky drvr Platinum Level Sponsor


    You mean this passage in the WSM? You should just remove the distributor cap, not the lead, then use a test light between the terminal and ground.


    The dwell is just a measure of how much time, in rotational degrees, that the points remain closed to allow the coil to charge its magnetic field. As engine RPM's increase, the actual charge time decreases. This could lead to poor performance at high RPM's because of poor coil saturation. The points cam with increased dwell moves the limit of saturation to a higher RPM.

    I got the 45* figure from the article linked above and I'm sure it is a generic statement about four cylinder engines including everything back to flat heads. The points cam shape in our Lucas distributors would be considered "high lift" to cause a faster rise and drop time to allow the increased dwell time for coil saturation. The downside is an increased penchant for point bounce at higher RPM's. Point bounce can be thought of as the coil experiencing a "partial fibrilation" - hurts spark energy at high RPM's. To give perspective, an engine turning 6000 RPM would be firing the points and coil 50 times every second. Which means the dwell time is about 0.01334 of a second to charge the coil for the next switching and firing impulse.

    The period of points closure is specified by the ignition system designer and is typically expressed as degrees of distributor rotation. In a four-cylinder engine, the angle between each ignition cam lobe is 90° and the period of points closure or "DWELL" is usually a bit over 45° of distributor rotation.
    Last edited: May 9, 2022
    puff4 likes this.
  5. beamdream

    beamdream Gold Level Sponsor

    Don't loose too much sleep over any of this, particularly if you're not in competition.

    Simply put, so long as the points open and close somewhere around the 0.15 thou mark you'll be fine, that will put the dwell angle in the ballpark. You will have to go a long way off these parameters to even notice any difference for daily driving let alone damage the engine.

    Main criteria with points are - if they dont open spark plugs dont function, open too wide and the engine will get fluffy as the revs rise.

    As to timing, if you get too far advanced you may get pinging (detonation) which if pushed too far will damage pistons, but you'll get lots of noises from the engine to alert you to this. If you go too far retarded performance will drop off and you'll notice it.

    Assuming your engine has some miles on it, best thing to do is set things up as close as you can to book specs and go for a drive, if it feels good be happy.

    Since the book specs were published half a century ago, there's been significant changes in fuel specs, this alone will have an affect on those numbers so don't get too bogged down in them.

    Ok, just picked up on your plug gap at 0.13 ? If thats the case they need to be opened up to about 0.25, possibly 0.30. No harm in where they're at but definitely not in the plugs efficiency range
    Last edited: May 10, 2022
  6. Barry

    Barry Platinum Level Sponsor

    Lots of good info in your post, but a plug gap of "0.30" is over a quarter of an inch. A plug gap of 0.025" to 0.030" will work; a plug gap of 0.25" to 0.30" will not.
  7. Acollin

    Acollin Platinum Level Sponsor

    Not sure I ever meant to mention plug gap in my question. I never checked the plug gap. My questions concerned point gap.
    No harm no foul!!!!

    So huskydrvr, the test light should be connected in sequence with the coil wire to LT terminal blade —the coil wire connected to the LT terminal blade.
    If so, Question: could I just as easily connect my test light to the appropriate side of the coil and not mess with the terminal blade on the distributer?
    Thanks all
  8. husky drvr

    husky drvr Platinum Level Sponsor


    Yes, connecting on the 12v coil terminal post wired to the distributor will be fine.

    Hope this helps,
  9. beamdream

    beamdream Gold Level Sponsor

    Hey Barry, good catch.

    Working with a 0.30 feeler guage would be awkward to say the least ;)

    Barry, my apologies, put another zero in front of my measures.
  10. Barry

    Barry Platinum Level Sponsor

    No apology necessary; the only people who never make mistakes are those who never participate. I've been there, done that and accumulated a stack of t-shirts.
  11. Tom H

    Tom H Platinum Level Sponsor

    Interesting that the WSM suggests removing the distributor cap and connecting the test lamp AT the distributor terminal, not the coil terminal. I guess they were assuming that you'll want the cap off in order to get to and adjust the points, and just felt while you were doing that why not connect the test lamp right there. Plus, with the cap off, the engine will not accidentally start while you crank the engine.
    Paul A likes this.
  12. beamdream

    beamdream Gold Level Sponsor

    Nor generate a big fat spark in close proximity :)
  13. Jay Laifman

    Jay Laifman Gold Level Sponsor

    For what it's worth, despite all my attempts to get the feeler gauge method to work, whenever I then checked the dwell, it would not be correct. So I first gave up and would do the dwell test only, and just adjust to get it right. Then when I rebuilt the engine about 26 years ago now, I got the Lumination electronic points. It's worked perfectly ever since.

    In the older Porsche world, there are those that say that the points and condensors currently available are not very good quality. So a lot of people ditch the points and get Pertronix. I have Pertronix in both my older Porsches, with no issues for almost as long as the Lumination on the Alpine. Though there are plenty of Pertronix naysayers who stick with points or always carry points in the car should their Pertronix fail. I have spoken with folks at Pertronix (who are of course biased). They say that their units really don't fail very much at all - unless there is another issue, like a worn and wobbly shaft (which is often why someone put Pertronix on in the first place) or the rotor was not put on correctly (for some cars, you need to file down the bottom of the rotor to get it to seat correctly with the Pertronix magnets on it.

    I wonder if there are similar quality issues with the points and condensors available for Alpines. Though 1960s stock Lucas may have started where Bosch 2000s points are now. Ha - just kidding. Lucas got a bad rap because the industry wouldn't pay for better quality - and I think what Rootes selected was better than British Leyland anyway.

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