Re: Replacement Ignition Coil
 

Gustafson, I don't have a dyno so can only do the idle test. I agree with you on the timing change possibility. That, or the original coil (or condenser) was weak.

Re: Replacement Ignition Coil
 

Nobody said that idle speed had anything to do with all out performance , its just a characteristic of the performance coils that I have used . You obviously have problems with reading comprehension . . .

Re: Replacement Ignition Coil
 

No, just trying to comprehend why a coil with higher voltage potential would increase idle speed when that higher potential is not being used; when both an original coil and a performance coil are providing the same voltage at idle.
At full throttle I can see an original coil not providing consistent spark, but the voltage demand is much higher than at idle. So I'm going to do the idle test and try to prove myself wrong.

Re: Replacement Ignition Coil
 

40 Deluxe, suppose a brand new coil fires a split second sooner when the points open, that would be the same as more advance. And something that would be both hard to measure and the resulting increase in RPM of no meaning; would love to know your test results
Mr Swoft how many would be concerned about compression blowing out a spark with a 4.2 head at 2200 rpm. A 10:1 head at 7K, that would be different .
Spark, timing, coils, points and such can be confusing and could be a great thread to clarify from. To many, timing and ignition and spark is just shoving a pin in a hole

Re: Replacement Ignition Coil
 

See the attached article though not sure how much science data is involved.. Perhaps it will help with Bob's initial ?. Note the sentence that the 2ndary output is around 100 x the primary voltage with other parameters in force as well.
Removed the attached, may be corrupted file. Go to MGAguru.com "Ignition Coil and Testing" and see if it opens.

Re: Replacement Ignition Coil
 

Why not ask Pertronix ??? Maybe they can clear up your confusion ... This is the last time that I will open this thread .

Re: Replacement Ignition Coil
 

One point not addressed in that article is the great variation in secondary voltage output. As the primary field collapses and induces secondary voltage, secondary voltage only rises to the amount needed to jump the plug gap. If 5,000 volts will fire the plug, that is what the coil produces, no more. If it takes 10,000 volts to jump the plug gap, that is what the coil produces. During my career as a mechanic, I've had many vehicles hooked to a scope and seen this. A fouled plug or a plug wire shorted to ground shows a very low coil output. An open plug wire or worn plugs with large gaps show higher output voltages. We also did a 'snap test', snapping the throttle wide open quickly. This also raised the voltage requirement significantly. If one cylinder showed an abnormal spike, it was the problem child.

Re: Replacement Ignition Coil
 

Well, I don't see how a new coil would fire any sooner. Electrical current would travel at the same speed in either coil. If anything, a performance coil likely has more turns of wire around the core, so current would take longer to complete the circuit but this would be insignificant, even meaningless.

Re: Replacement Ignition Coil
 

LOL TOM! I have yet to install my flamethrower coil.I lost all spark 2 year ago and after the car cooled down she fire up.. It's not done it since.

Re: Replacement Ignition Coil
 

OK, did my idle test this afternoon. I did it on my '40 Ford, all stock with the exception of a remote coil adapter on the original helmet distributor. The coil is a 6 volt 1.5 ohm Echlin of unknown vintage, but old. The engine idled at 610-615 RPM. I then mounted a new out of the box 12 V. Bosch 012 coil and powered it with jumpers directly from a 12 V. battery. The engine idled at 595-600 RPM. Reconnected the first coil and idle RPM went to about 605 RPM. Revving in neutral, both coils sounded the same.
So no RPM increase for me.

Re: Replacement Ignition Coil
 

File Type: pdf Ignition coil function and testing.pdf (169.7 KB, 19 views)

Comes up blank

Re: Replacement Ignition Coil
 

see post 45 for article web location.

Re: Replacement Ignition Coil
 

The picture looks like a slant pole coil. I got one (at Hershy) for my 29 tudor because it was correct for that year. My tudor practically sighed with delight when I installed it. It started better and ran better. Glad I am set for the next 90 years!:D

Re: Replacement Ignition Coil
 

duke36, thanks, I found it.

I've been testing a bunch of old 6 volt coils and also some 12 volt ones that call for a ballast resistor, but not using one and testing them using 6 volts.
They all put out around 25KV, some as high as 28 KV.
For testing I use an old GM distributor clamped in a vise and turn the shaft by hand to open and close the points.

I've been using a tester similar to this one: