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Thread: ? Timing Light Myths ?

  1. #1
    JCT Guest

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    I have had several people tell me different things about using timing lights on MSD Ignitions. Lets hear myth busting facts.

    Adjustable timing lights... will they work or not?
    Non-Adustable timing lights... are they the best suited?

  2. #2
    msdtechsupport1 Guest

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    We recommend using non-adjustable timing lights because of their analog circuitry design. Adjustbale digital type lights tend to pick up interference from the MSD and can be off as much as 1 degree per thousand RPM.

  3. #3
    JCT Guest

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    Thanks very much for the reply. Maybe this will settle things around here!

    Jay

  4. #4
    Join Date
    Jul 2003
    Location
    Seattle, WA
    Posts
    303

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    I think there may be a more specific answer to the question about digital timing lights. Some of us have inquiring minds and want to really know what the deal is. I doubt if one type of light is more likely to pick up interference than another. What is far more likely is that at idle, a CD ignition puts out 8 sparks or so. Digital lights may start triggering on any one of those 8 sparks erratically causing the mark to jump all over the place. Analog lights are more likely to see the cumulative effect of the spark group as the trigger signal. One manufacturer even offers a tune up feature on a CD ignition that tells the unit to only output one spark per cylinder just so that any light will give good results. Besides, the real reason for owning a dial-back timing light is to check your distributor advance at high RPM. Normally you would not have timing marks out past 10 degrees or so. If you are not running a vacuum or mechanical advance distributor, or don't want to monitor your spark advance at high revs, save your money and get a standard light. Hope that clears up a few questions.
    -Lazarus

  5. #5
    Join Date
    Aug 2018
    Location
    Canada,Ontario
    Posts
    1

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    I apologize for bump the old topic, but I have some interesting observations that I would like to share, maybe this will help someone in the future because once I was on the lookout for useful advice.
    Here are some Engine issues that my timing light told me about .Spark scatter due to badly worn distributor shaft with points ignition. (Dwell meter would have pointed this out too,)
    Upside down centrifugal advance weights.
    Worn centrifugal advance mechanisms.
    Seized mech advance mechanisms.
    Pooched vac advance canisters ( with mityVac pump).
    Outer damper ring slipping.
    Vacuum advance canister installed where a pressure retard canister was called for ( Turbocharged Corvair).
    Adjusting a few centrifugal advance curves.
    Testing coil wires, dist cap and rotor in No spark at plug situations.
    Testing for spark in intermittent electronic ignition module failure situations.
    Setting ignition timing of aftermarket CDIgnition on dirt bike that required repositioning the magneto rotor and running key-less.

    As far as accuracy, it's always a nagging worry. The best I have is comparing 2 lights, after a wary informational static timing check when possible, since worn components can allow several degrees change when running. The old self powered orange Xenon light my dad gave me over 40 years ago seems to be pretty consistent so far.nce I run MSD unit https://mechanicguides.com/best-timi...-msd-ignition/ I use a non dial back light, since the digitals won't work on MSD, and a timing tape to plot curve. and BTW, always use the positive stop method to first find TRUE TDC.
    Tuning articles all over the web and in mags will tell you how much @ what rpm for all sorts of engines and builds from dyno tests. Those guys with the dynos can figger out just what the engine likes better than my ear, and the closest drag strip is 60 miles away, makinf that method inconvenient at best.
    So I value a good timing light highly.

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