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Prestolite Dual Point Advance Curve BACKS OFF! (retards 4 degrees)

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  • tomhoo
    replied
    Yes, I know the capacitor is irrelevant with a module, however, it's still an interesting conjecture.

    It appears both of my Heathkit ignition analyzers (one tube, one solid state) both work(!)

    What is interesting is that with my single points with dwell around 28*, does not behave like like the ideal waveforms.

    The ringing after the spark extinguishes is a damped sinusoid, however, it never damps to zero before the points close - and that is around idle speed. When you increase rpm, the dwell eats up the same portion of the 45* available, but the spark is a fixed duration which means as rpm is increased, the portion of the remaining 15* for the points to damp out the coil gets smaller and smaller. Around 4000, there is about 1/2 a sine wave and the points close.

    Now the frequency of the ringing is maybe 1/2 that of the pictures I've seen of an ideal waveform. The capacitor in the Delcos was .194uf which I thought was low - but the other Delco had the exact same capacitance. The Presto caps are around .24uf if I remember.

    I'm tempted to swap caps to see what it does to the waveform.

    ___________________________

    RE: Presto Weight Fix: Another fix would be to fab limiting stops into the bottom plate so that the cam plate does not limit the weights by the pins. If the stops engage the weights in the plane through their CG, the pin wear would be even and even when worn, the weights would do their job.

    _______________________

    RE: Dwell Meters that can work on a distributor chucked in a lathe: I have a Knight Kit Auto Analyzer that can do this either in a running engine or a distributor being spun on the work bench. This is not a common feature. I'm eyeing up a "newer" Knight 375A...

    Leave a comment:


  • bezhawk
    replied
    Originally posted by tomhoo View Post
    I have to laugh. I don't think I've seen one comparison of points conversion modules on an ignition scope.

    And I believe with a scope, it is possible to determine the optimal condenser size for a given coil.

    But no one's talkin'
    But, you only need a condenser if you are running points with that coil. With a points replacement module, you do away with the condenser entirely.

    Leave a comment:


  • tomhoo
    replied
    I have to laugh. I don't think I've seen one comparison of points conversion modules on an ignition scope.

    And I believe with a scope, it is possible to determine the optimal condenser size for a given coil.

    But no one's talkin'

    Leave a comment:


  • Dan Timberlake
    replied
    I think some of the points conversions maximize dwell and whack the stock coil with a pointed stick with a rusty nail in it for genuinely enhanced performance.

    Leave a comment:


  • tomhoo
    replied
    Back when I was a child, amassing my hoard of "hard" parts, the Delco was taken for granted. Only recently, did I realize it was only available for 2 years.

    And then there is the non-Delco single point distributor.

    Why? Oh, Why?
    _____________________

    Back to business...

    I'm thinking any of these "points conversion" modules. If they are nothing more than an electronic switch, the problem of dwell and wimpy coils is still present.

    I've never tried on of these 40 or 45k coils (I think there is a 58k canister out there too). I have an Accel 140001 - actually, it's from the Delco HEI conversion kit that lets you run an external coil (ugh! that was when I lost all faith in Accel and aftermarket ignition in general...) But it is academic - I'm not putting that bumble bee under my hood for all to see and jeer at!

    Leave a comment:


  • geoffgogle
    replied
    1962 was a sad year for studebakers enviable reputation as possibly the car least likely to leave you stranded on the side of the road--particularly if the road was in the heart of central africa in the zambezi valley bordering both zambia and zimbabwe and teaming with REAL WILD ANIMALS---1962 WAS THE ADVENT OF PRESTOLITE DISTRIBUTORS--GENERATORS[ALTERNATORS IN 63] AND STARTERS--THE GENS.AND STARTERS WERE O.K--THE DISTRIBUTORS AND ALTERNATORS WERE ABYSMAL--TALK ABOUT THE WEAKEST LINK LETTING THE SIDE DOWN//

    Leave a comment:


  • tomhoo
    replied
    UPDATE:

    Simply cleaned up my Delco that was setup maybe 20 years ago.

    It is a joy to see rock steady timing and a proper advance curve.

    Nest step it to decide on which Pertronix to use. Can get a good deal on an Ignitor I and will probably go that route although I'd like to try the III.

    Then there is the bypassing the PINK resistance wire - I detest working under the dash of the 63 Lark. Tempted to install a lug mounted 12v 20 amp relay at the coil so I don't have to deal with the ignition switch.
    NOTE: If I have to tap into the ignition switch, it might be worth the effort to conveniently locate a "sub-box" for the IGN and ACC terminals that would make any future electrical mods easier.

    RE: Presto weight/timing issue:

    The problem is that that top for the weights is the end of the the cam plate slot. When this happens the force on the top and the centrifugal force on the weight CG produces a couple that is reacted by the pins. The result is that you get wear that allows the weight to "curl" upward.

    Note that before the weight hits the stop, the centrifugal force is reacted in-plane with the springs so there is no couple.

    A solution to this would be to shim the cam plate so that it is very close to the weight top face so that when it wants to lift, it hits the bottom of the cam plate. Unfortunately, this would required shims to be placed under the cam plate clip (and reducing the thickness of the shaft spacer the cam plate rests on.

    While it would be interesting to solve all these issues, I don't have the time or money to invest in this "Presto hobby."

    Leave a comment:


  • tomhoo
    replied
    UPDATE: Checked timing with hardly used, babied Sun timing light and it completely agreed with the Sears Penske.

    Also learned that Mallory's 61001M is a point eliminator. If I had to pick between Mallory, Crane, and Pertronix, I'd be compelled to pick Mallory even though I've never liked their products.

    I also tore down my spare Presto and it was as I suspected, the cam plate slot limits the weight travel. This is a reaction that is out of plane with the CG so that the weight wants to "curl" up when it is limited. I was hoping to rebush the weights, but the bottom face is worn too. Not worth the effort to repair (of course, I haven't priced new bushed weights - would not be surprised that they are $50 a set - heh heh)
    _________________________

    DELCO WINDOW:
    I was looking at my 2 Delco's and they do not have roll pins in them. One I remember re-pinning after shimming and I used welding rod with mushroomed ends to retain, the other looks factory where the pin was quite mushroomed with a heavy grid pattern where pressed. I know they are supposed to be shear pins, not sure what to use. Also, the one I shimmed, has excessive end play when originally set to .005-.010 inches. Don't know where all that wear came from.

    Maybe I'll just clean up the Delco and put it in to see what the timing does.

    Leave a comment:


  • tomhoo
    replied
    UPDATE: Just borrowed a like new Sun timing light to break the disagreement from my other two timing light readings.

    I'm totally undecided what way to go:

    LIKES:
    • OEM look
    • OEM HEI systems
    • Delco Window Distributors
    • Delco HEI Distributor performance
    • Pertronix & Crane modules that don't use an external box (OEM look)


    DISLIKES:
    • Points and condensers (they are getting just too expensive compared to electronic)
    • Prestolite Dual Point with its bushing issues (shaft and weights)
    • External ignition boxes
    • Delco HEI Distributor looks (hideously non-OEM look)
    • Pertronix Ignitor III is over $100 which is too much for inferior to OEM aftermarket stuff.

    Leave a comment:


  • PackardV8
    replied
    Pertonix has it's fans, but I convert them to the Mopar solid state trigger.

    FWIW, it costs me $300 to completely rebuild one correctly with all new parts.

    Jack Vines

    Leave a comment:


  • tomhoo
    replied
    I don't think I have point bounce or float around 3000-ish. The springs of my points are much stiffer than the Standard X suffix points.

    Timing is pretty solid and does not jitter much at all, maybe 1*. NOTE: I have power steering which is a real pain to see timing - it is not possible to look on a radial line, so there is parallax error.

    Now hearing this about "new" caps failing, given the cost of points/cond, I'm really leaning towards Pertronix (but which one) or the Crane XRi which seems to have lots of complaints on the internet.

    I could make a hobby of getting the Presto right, but seriously, why should I do that? Even points for the Window are almost $20 which is totally insane in my world. And then there is getting HD ones and how do they vary? Pointless definitely has advantages. And seeing how my "points" have almost stranded me a couple blocks from my home, there is no argument that points are more reliable. I put this all in the "50 year old failure modes" category.

    Leave a comment:


  • Bud
    replied
    If you have a scope, I recommend using it to look at what is happening with the ignition. A variation in dwell at different engine rpm is definitely a cause for concern as it shows either you have excessive wear on the distributor shaft and bushings or you could have a problem with point bounce or float which will give an unsteady dwell reading. If the dwell is changing then it's a guarantee that the timing is changing. If your scope doesn't show anything, then it's time to find someone with a distributor machine to check out the distributor. Also keep in mind there have been several people reporting including myself about new stock condensers failing shortly after they were installed. Bud

    Leave a comment:


  • tomhoo
    replied
    Ah, a dwell change... I would like to answer that question. If dwell changes due to point contact duration, then there is a 50/50 chance the timing would change (depending on which point was varying.)

    I actually have two of those Heathkit Ignition Oscilloscopes - might be time to break one out and use it.

    I'm also warming up to the Window w/Ignitor and FireBall III Pertronics...

    Leave a comment:


  • Dan Timberlake
    replied
    An oscilloscope would probably be required to reveal the symptom, if not the disease, but certainly a wacky unsteady dwell reading would indicate there is indeed "a problem."

    Leave a comment:


  • WCP
    replied
    Does a dwell change coincide with the timing retard observed?

    Leave a comment:

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