thanks Dyke , —- , I did not say but know if pertronix etc die , you walk , unless an extra one , but even then — change on road ? on back of hemi ?at night I don’t think so . All the pertronix require different different matching coil ohms too . Points never die , really . They get mangled and poorly adjusted . imho even bad looking burned points run just fine if dwell reading is right . And they meet fairly square .
Stories about how great it runs with new ones get filed under rain dance . Yeah it does rain sometimes after the dance , —- (because dwell is right )
After all these years poor ignition is either the lousy intermittent capacitors with rubber cones put in our cars, often long ago , as part of “a tune up” —- or else a prior testing run of the ignition unloaded —- by trying to arc a wire to frame “to see spark “ . Normal volts with a plug load is limited by plug gap to under 20000 volts , it drops to a few thousand once plug does arc ( like a welder ) , but an open wire held in a hand too far from ground even once will let volts inside the coil winding go to 40-50000, which can break down the internal coil insulation . Now you have a carbon track residue inside the coil ,— a coil that was fine before you did that — which will arc over randomly and then fix itself etc etc as oil inside gets involved . It will even jump out of the tower to reach the primary nuts , trying to reach ground . I have seen that on a 440 when a plug wire fell off at night . Imagine inside the small spaces in the winding …
To see or test the spark use an old spark plug with a solidly attached 2 foot ground wire with clip and connect it solidly . Or an ignition tester neon type thing that does same thing .
I see on our site , guys saying they “ arced it to ground “ , — well ——high probability you just wrecked your coil inside and now you have two problems at once . Intermittent ones .. I did that , in past years , before realizing what it does .. Thanks again John
PS , l think the fact that Petty and Kiekhofer , Daytona records etc were all set with points says leave it alone . And you can fix it in 20 minutes .
“ parts that are not there ( especially electronic ones) do not break down” Sent from my iPhone On Aug 16, 2023, at 12:13 PM, ridgleyracing65 <ridgleyracing65@xxxxxxxxx> wrote:
John: All great points described in a manner that members can understand them. Most everybody with old cars understands the basics of point/condenser ignition, but very few comprehend the nuances of coil resistance and dwell variations. Agree fully with the comments about MSD reliability (even though we still use them in vintage race cars and always have plenty of spares). However, we trigger them with the old Chrysler pickups and reluctors. As an aside, I have had good success with Pertronix I units, but experienced failures with Pertronix II and III systems. Pertronix I units work fine with solid core ignition wires (despite what they say), but the II an III systems definitely REQUIRE suppression wires.
Dyke Ridgley
On Wednesday, August 16, 2023 at 10:45:18 AM UTC-5 jkg wrote:
Hi Rich , correct data , however the DC resistance of the ignition coil ohms is in series with the ballast , lowering the current ; .6 ohm in 12 v would be 20 A , and your 10 A number probably assumes about .6 for the coil , about right . However at idle the dwell time closed ( time per spark — not degrees) is very long , the coil saturates and the current rises , per spark , the ballast gets hot and current drops a lot to protect points and coil . Especially if ignition is on motor not running points closed (!) . That situation pops a marginal ballast. This is why you should never put a “ high performance “ coil on the car without knowing the resistance of the new coil primary . Low aftermarket ohms , in an attempt to get hotter spark , will burn out ballast and burn points . And not give you a hotter spark either . It is well designed , just as it is .
What helps with a hotter spark is more angular dwell at high rpm , why mopar dual points . That second set closes early , single point you have to wait to close as it goes over bump of cam , translates to maybe 15-20 % more time to “fill up “ the coil magnetic field , a fixed time set by physical coil L / R ratio —- on the order of 2-3 milliseconds . So that dual point gives you 15-20 % more rpm before the same spark fade ( % varies , just an example ) . Direct AB comparison of 300B distributor on a 354 on dyno vs best MSD made showed zero difference in HP ( 600$?— for what ? more troubles?) , at 5800 rpm . I saw this personally only because MSD failed on the dyno tun . … as they are prone to do in cars too) ; guy who owns dyno said “I see that all the time” . A curse for Chevy guys .., They DO see better with MSD , right up there with stock mopar . We adjust points and keep going just like new
They were ok for Petty at Nascar , ok for me too . Very fussy to get right you need a dwell meter . Agree too , ballast is either ok or dead , rarely would come and go . That is typical of capacitor , which then gives a very weak spark . jg Sent from my iPhone
The last one I had fail was years ago, so I'm going by memory.
The failure was with an open back ballast resistor and as I remember, the resistance wire was broken along with the ceramic rod that the wire was wound around. If I had to bet, I'd say the rod broke first. Probably running a little hot and then got wet.
I have seen a few fail on other cars were there was actual physical damage to the ceramic block itself and that let the terminals flop around until the connected resistance wire failed, probably from vibration. How they got damaged in the first place was anybody's guess. Although I think I might have broken one on my own car during a late night engine swap.
John
On Tuesday, August 15, 2023 at 08:06:11 PM EDT, Rich Barber < c3...@xxxxxxx> wrote:
Many/most electrical problems are at connections. The ballast resistor has good solid connections to spades on each end plus two connections inside the ceramic housing joining the resistor wire to the spades. The ballast resistor on our K is open at the back to allow heat transfer and some protection from underhood environment. The resistance wire itself may deteriorate after years of service at high temperature and vibration. Has anyone examined a failed resistor to see what failed? I would think intermittent connection of resistance wire to be unlikely. I just measured the resistance of the ballast resistor on our 300K at 0,6-0.7 Ohms on a 200 Ohm scale. FSM spec’s are 0.5-0.6 Ohms at 70F-80F. At 0.6 Ohms, it would take a 10 Amp current to the coil. Seems a little high. Nichrome resistance wire (if that’s what we have) Resistance and therefore, Voltage drop, increases with operating temperature. Over 90F in garage today. 102F outside at 5 PM, PDT. Rich Barber in CA
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