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Distributor Gear Off Half A Tooth
https://slantsix.org/forum/viewtopic.php?t=57785		 Page 2 of 2
Author:  Old6rodder [ Tue Jun 02, 2015 11:45 am ]
Post subject: 
I ran across a wide contact cap some time ago that I use on my Toad engine for this purpose. Could be an even easier adaption than cobbling a rotor.
The contacts're only aluminum (though appear to be holding up well), and I know nothing of it's parentage, so can't guide you toward one should you wish. Certainly someone else here'll know more about'em than I do.

My own (back yard of course) response to your situation'd be to make the pick-up position on the plate adjustable for rotation (having had to do that for various point sets in the past), shouldn't need much movement.
Author:  SlantSixDan [ Tue Jun 02, 2015 12:16 pm ]
Post subject: 
The wide-contact cap (2098 765 black bakelite, then 2444 690 tan alkyd) was used with a long/narrow-contact rotor (2098 770) as part of a service package (2448 273) issued in 1962 to combat crossfire during cold starts. These parts were factory equipment until 1966 when they reverted to the narrow-contact cap and regular-contact rotor for unexplained reasons—probably because the upgraded alkyd cap material's improved dielectric strength and resistance to carbon tracking made the wider contacts superfluous. There was limited service of the wide-contact cap and rotor in the aftermarket, and always with aluminum cap contacts rather than superior brass, bronze, or copper.

Much though I wanted to, because "hey, cool!", I've never found an actual operational improvement or difference with the service package parts vs. the narrow-contact cap and normal-contact rotor…except in one particular case. My '62 Lancer was an extremely low-miles car when my father bought it. Still with its original early-production first-version cap and rotor. Narrow aluminum contacts, black bakelite material, 1889 424. Crossfire city in cold starts. The service package, which I hunted down, solved the problem. But so did every subsequent narrow-contact cap and regular-width rotor I ever installed.

All of that said…why are we making such a big to-do about this what might be objectionable in theory, but doesn't cause any actual problems in how our engines run?
Author:  Reed [ Tue Jun 02, 2015 12:26 pm ]
Post subject: 
Quote:
why are we making such a big to-do about this what might be objectionable in theory, but doesn't cause any actual problems in how our engines run?
Image
Author:  Old6rodder [ Tue Jun 02, 2015 1:51 pm ]
Post subject: 
Can't speak to that, merely responding to the concept.
Exercise in hair splitting? :lol:
Author:  DonPal [ Tue Jun 02, 2015 3:46 pm ]
Post subject:  Myron Would Reveal At A Nice Long HEI Spark Duration
Thankfully HEI gives a nice long spark duration in addition to the increased intensity. So Myron's 3 shot actually has involved probably into one long one?

After studying the vacuum advance it pulls the reluctor and rotor relative to the cap another 10 dist deg.

So consequently the combined mech and vacuum dist degrees are 20.
All told that would require 1/4 inch rotor offset in both the after (at idle) and before (at cruise) plug tower electrode location with the crank set initially at 10 BTDC crank deg.

Said another way the concept rotor you describe would need to reach over in each direction 1/4 inch more to be pointing at the electrode centerline.
And that's if everything is perfectly setup within shop tolerances.

So the compromise made by Detroit and the likes is the current cap electrode width and rotor width with a less than optimal initial "after" plug tower electrode rotor position at idle.

Whether this hurts life and spark intensity is then the question.

I know my ECU's don't last long and so I dropped the plug gap to .040 which has dropped the measured spark voltage almost in half ...hopefully making the coil and ECU want to live longer....the thinking might extend to the gaps at the distributor???
Author:  SlantSixDan [ Tue Jun 02, 2015 4:27 pm ]
Post subject:  Re: Myron Would Reveal At A Nice Long HEI Spark Duration
Quote:
Thankfully HEI gives a nice long spark duration in addition to the increased intensity. So Myron's 3 shot actually has involved probably into one long one?
Doubt it. What it probably did was severely degrade the pulse signal the ECU was looking for, thus degrading the spark quality.
Quote:
Said another way the concept rotor you describe would need to reach over in each direction 1/4 inch more to be pointing at the electrode centerline.
Who says it has to point at the centerline? It doesn't.
Quote:
I know my ECU's don't last long
What ECUs are you buying?
Author:  DonPal [ Tue Jun 02, 2015 6:59 pm ]
Post subject:  What ECU
NAPA TP45 ECU driven 70 miles per day, 350 miles/week last about 2 years with the .045 plug gap.

The one recently installed on my daughter's 65 Dart broke down after less than 100 miles.

There might be a quality problem?

Plug Electrode Centerline is just a point of reference. This picture shows for my test stand engine rotor relationship that there is no part of the electrode lined up with any part of the rotor in the mech and vac. advance all in stage:

http://s296.photobucket.com/user/184pal ... 4.jpg.html
Author:  nm9stheham [ Wed Jun 03, 2015 11:02 am ]
Post subject: 
The electrons don't care in any fashion if they are flowing through the center of the electrodes or off to one side. The arcs will move all around the electrodes anyway. So as long as there is any overlap, it won't change anything.

And the rotor arc is not what limits the spark current; once it is established, the arc resistance is relatively low and the spark current is set by external factors, like the coil's discharge rate. This is likely why Dan did not observe any difference in later cap/rotor combos in that old Lancer; they all fixed the crossfiring issue, and did not effect the actual normal spark energy movement.
Author:  SlantSixDan [ Wed Jun 03, 2015 2:08 pm ]
Post subject:  Re: What ECU
Quote:
NAPA TP45 ECU driven 70 miles per day, 350 miles/week last about 2 years with the .045 plug gap.
That's definitely an early failure.
Quote:
The one recently installed on my daughter's 65 Dart broke down after less than 100 miles.
That's a VERY early failure!
Quote:
There might be a quality problem?
Might easily be, given the downward slide in parts quality. But make sure you're giving the module a fighting chance to survive. Undervoltage will heat it up (so use a relay to feed it). Poor ground will scramble it (so make sure you have an excellent ground). Excess heat will cook it (so use a heat sink, not just the fender metal).
Author:  SlantSixDan [ Wed Jun 03, 2015 2:11 pm ]
Post subject: 
Quote:
The electrons don't care in any fashion if they are flowing through the center of the electrodes or off to one side. The arcs will move all around the electrodes anyway. So as long as there is any overlap, it won't change anything.
True.
Quote:
And the rotor arc is not what limits the spark current
True, but it will affect spark voltage. The larger the gap, the higher the voltage required to jump it. This is why series-gap spark plugs used to be available, to raise the electrode gap voltage high enough for the plug to fire even in a combustion chamber full of oil. It's also why for any given secondary voltage, using the long-tip rotor allows you to open the plug gap -- you make the rotor-to-cap gap smaller so you can make the plug electrode gap bigger which gives running/driveability benefits.

But this effect is also why cap/rotor phasing can matter. If the rotor's way out of phase with the cap contact, there's a relatively giant gap for the spark to jump, which will push secondary voltage up way high. If it's beyond the capability of the ignition coil, the result is misfire. If it's within the coil's reach but beyond the dielectric strength of the coil, coil wire, rotor, cap, or plug wires, the result is arcover and misfire. Even if it's not beyond either limit, higher voltage = more wear and tear on the entire secondary side of the ignition system. That's why a wing-tipped rotor might not be such a terrible idea. Here, for example, is what the rotor looks like on the 3.0 V6 in my '91 Spirit:

Image
Image
Image

Nice wide contact end. Toothed on the premium version to reduce arcover voltage needed to jump from rotor to cap. It would be keen if such a rotor could be made for the slant, but it would surely be a strictly make-it-yourself affair. (The more I look at these pics, the more I think it might be feasible to buy a 3.0 V6 rotor, disassemble it, cut/drill the contact piece as needed and install it on the \6 rotor, then insulate all that newly-hanging-out metal with some epoxy or Sugru, which is amazing stuff)
Author:  nm9stheham [ Wed Jun 03, 2015 2:21 pm ]
Post subject: 
OK, the point for the OP was that as long as the rotor and cap electrodes overlap each other some, the gap will be the same and the arc will still be established the same. So no need to obsess on things being center-to-center.... which has been pointed out.

Good point on the voltages...... makes sense.
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