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Article: Points and Pertronix

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Whoops, sorry, wrong forum!





Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild



Edited 1 time(s). Last edit at 2019-02-10 11:08 PM by TR3driver.

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A Brit in Bama Avatar
A Brit in Bama Keith Norrie
Eva, AL, USA   USA
While I'm back to points (following a rebuild/recurve by Advanced Distributors), and will continue with them, I did use the Accuspark set up sourced from the UK for 3+ years, and found that it is not as vulnerable to leaving the ignition on as Pertronix apparently is.

The set up was 100% reliable in use, and I did leave the ignition on for 30mins one time.

I carry a spare points plate as well as the old Accuspark plate around in the boot, just in case....

Marksg1 Avatar
Marksg1 Mark Greenbaum
Evanston, IL, USA   USA
1976 Triumph TR6 "Nigel"
I've had a Petronix for 3 years, no problem even when I leave the ignition on for diagnostic work. BTW, I see that the newer Pet II and III have overload/burnout protection built in. Are these TR6 compatible?



I love the smell of hydrocarbons in the morning.

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maxd Avatar
maxd Bill Davenport
Fort Pierce, FL, USA   USA
I've read that the II wont fit in the Triumph distributer.
Bill

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
What I notice about factoty OE ignitions are large often elaborate, Aluminium heat sinks and shielding.

I assume what is killing Petronix and their ilk when the ignition is left on (not a good idea regardless) is that they over heat, and if there is one thing modern electronics don't like it's heat (the other being electromagnetic interference )

It might help if a heat sink paste were used when mounting a petronix, but honestly I don't think those big expensive factory heat sinks were used for fun!


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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1595848 by Marksg1 I've had a Petronix for 3 years, no problem even when I leave the ignition on for diagnostic work. BTW, I see that the newer Pet II and III have overload/burnout protection built in. Are these TR6 compatible?
https://www.bpnorthwest.com/pertronix-ignition-ignitor-ii-22d6-e-type-64-to-70-tr250-tr6.html



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

Fogspawn, CA, USA   USA
1974 Triumph TR6 "Machine"
You’re right, Tony. Also thinking... the OEM systems
likely have more “stuff”, that is to say, feedback circuits
built in... analagous to thermal protection in electric motors and such...
For the low cost of subject ignition device, they happily
burn themselves up so you can buy another post haste...

more seriously, I tried implementing it before sorting other
matter out... Pertronix won’t help with bad timing, plugs, vac leaks,
badly sorted carbs etc. In their “defense” a number of us
don’t sort out the ballast wire issue, as simple as others make it seem...
My attempts at Pertronix each lasted 5 minutes... then a very rocky
intermittent ignition, but I did make it home, twice.
Points for the time being and happy.
w

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
Back in the 70's I earned some Beer money helping with a test of aftermarket electronic ignitions for a popular Motoring magazine.

The conclusion was, they were all pretty unreliable, some giving up the ghost during the short test.

BUT the advantage most of them had (some still used the points as the trigger) was that the points relied on the accuracy of the distributor cam AND the lack of play in the distributor shaft in order to give accurate ignition timing on ALL cylinders.

The car we were using as a test mule was quite new, (Morris Marina) but even so, there was a LOT of ingnition scatter.*
We fitted two brand new lucas distributors before we got the scatter down to only 4 degrees!
(I have noted 6 cyl distributors tend to be even worse in this respect)

Accurate ignition timing means that more ignition advance can be dialed in before pinging starts (once pre ignition starts, it tends to continue) with benifits to both power and fuel economy.

* The scatter appeared in two ways, uniform variation in timing between cyls at all rpm, and decrepancy at higher or varying rpm (points bounce or shaft wobble)

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
It seems like it would be easy enough to reduce scatter by replacing the bushing in the distributor housing. Anyone tried that?



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
Yes I have done that, when the possible wobble on the distributor exceeded the point gap :-(

Even a new bushing allowed to much play due to wear on the shaft itself.

Longer oillite bushing were pressed in that would bare on an unworn area of the shaft. The bushings were also reamed to a precise fit.
However the timing still differed (about 2 degrees) between cyls due to distributor cam inaccuracies.

Points do exert some side thrust on the shaft which combined with lack of maintenance (how many owners bothered to oil the distributor?) results in wear to something that was not that precise in the first place.

dicta dick Taylor
Downey, Callifornia, USA   USA
As to the accuracy of the timing, one can attach the inductance pickup clamp of a timing light to the plug wires to pickup the flash at each of the "newly marked" numbers on the timing damper. If you don't have these extra "0" stamped every 120º on the pulley, using #1 and #6 plug wires can at least tell if these two cylinders are receiving their spark at the same time when set to idle at "0" or close enough to see variances.
Lots of different ways to confirm or at least know if your timing changes between cylinders. For those who want to take a little time, fan blades can be chalk marked to pick up the timing light flash, rather than deal with extra marking of the damper. Stopping or bumping the engine over to "0" will show which blades to mark to be viewed by the strobe light.

Before replacing the two bushings on the distributor shaft, my timing between #! and #6 varied as much as 6º at certain rpm. Now the changes are within one degree. Can I tell the difference in the seat of my pants? No. But I feel better knowing that it's "right".

Dick

barry s Avatar
barry s Silver Member Barry Stoll
Alexandria, VA, USA   USA
1972 MG MGB GT
1974 MG MGB
1976 Triumph TR6
1980 MG MGB
I use and have always used points on all my LBCs. Never have and never will try electronic ignition. One might call me biased.

No one that uses points carries a spare distributor. If points fail they can almost always be re-gapped to get back underway. Carrying a spare condenser may be wise but current condenser quality is always in doubt.

Effective point gap can close over time due to plating transfer from one point to the other as well as cam block wear, neither rapid occurrences. I've never heard a suggestion that point gap need be checked on each cam lobe.

Distributor shaft wear will adversely affect both point and electronic ignitions.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
"Distributor shaft wear will adversely affect both point and electronic ignitions."

No! At least, not anywhere near the same degree.

Take as an extream example of my very worn distributor where the shaft wobble was equal (or even exceeded) the point gap of .015"
It was possible that the distributor cam could completely fail to open the points at all, let alone early or late, depending on how it wobbled. Dwell could also be reduced to virtually Zero.

With EI (weather Hall effect or Optical) such scatter could only result in an advance or retard of about 2 degrees.

Imagine the Optical splitter or Hall effect trigger on the distributor shaft. as each trigger rotates 360 degrees it's circumference travels a distance of about 3 inches from triggering to fire again on any particular cyl. With .015 wear on the shaft that trigger could possibly arrive .015" early or late. That is .015" over about 3" Not very much!

It is relatively easy to manufacture a splitter or reluctor (trigger) with slots or fingers exactly 60 degrees (6 cyl) or 90 degrees (4 cyl) apart.

Whereas to make a distributor cam whith 6 lobes and each has ramps so even that they will open the points within a couple of degrees of rotation of each other, is asking a lot! Especally after 40 years of wear.

For what it's worth, on my daily driver vehicles that my wife and I drive, we do not carry a spare distributor either (thats if my wifes car HAD a distributor :-) ) We don't even think of it! AND my daily driver truck is almost 35 years old and has never had ignition problems or adjustments. That said, if I used Petronix or any other 'popular' brand of EI I might consider a back up ;-)

POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
My '71 XJ6 had the same Lucas dizzy as the TR6, but while the TR requires an upper and a lower bushing to facilitate a tach drive between them. The Jag does not have a dizzy driven tach so it's distributor has just one full length bushing. My high mileage example had virtually no wobble most likely because the shaft was supported so much better than the TR's. - Pete

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