Another coil question please

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Model T Ford Forum: Forum 2017: Another coil question please
Top of pagePrevious messageNext messageBottom of page Link to this message  By tommy coffey on Sunday, November 12, 2017 - 04:35 am:

Opinions please on coils. Tested(not by me) on "Strobo-Spark". Tester says good spark current and spark pattern. Capacitor value 0.11-.017 (more than one coil) low leakage. Set at 1.1-1.45. Sound good or no?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Kossor - Kenilworth, NJ on Sunday, November 12, 2017 - 07:10 am:

No. The capacitor value is too low; should be 0.47 uF. The point contacts will be vulnerable to arcing and wear out out at an accelerated rate due to excessive arcing as the points open.

Point arcing also causes random delay in coil firing time which causes random ignition timing variation that degrades engine performance. Coil arcing is immediately apparent when coil firing Time is measured.


Top of pagePrevious messageNext messageBottom of page Link to this message  By tommy coffey on Sunday, November 12, 2017 - 11:42 am:

Maybe worth changing the condensers if the points are new or good?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Keith Townsend ; ^ ) Gresham, Orygun on Sunday, November 12, 2017 - 04:03 pm:

Yes.
Replace the capacitors, make sure the points are opening and closing squarely, with the proper point gap and cushion Spring gap. You may need to shim the point spacers.

: ^ )


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Sunday, November 12, 2017 - 09:57 pm:

Are these new to you coils? If they are your coils and have a history of working well in your car I would leave them alone. If the history is unknown then fix them as others have indicated.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, November 13, 2017 - 04:20 am:

Tommy:

I suspect the coils you have might be some of the "late" KW coils built new as late as the 50's or 60's. They can be identified by the core design of the winding. Look at the protrusion of the coil core through the hole in the top of the coil under the lower point contact assembly (called the vibrator). Typical T era coil core was a round bundle of iron wires formed very tightly together into a circular shaped core. The "late" KW coils instead have flat iron pieces of metal as the core. Those metal pieces are about 1/4" wide and stacked tightly on top of each other and then sideways too to form a somewhat circular mass of iron that is then the core. These coils also typically have a high resistance in the high voltage secondary winding. An ohm meter connected between the 2 side connections of a regular T coil will measure something like 3200 ohms or so while the flat core "late" KW coils will be closer to 9500 ohms on the same measurement. If you find your coils are this type then they also typically had a .18 uF capacitor used in them. Changing the capacitor may reduce the arcing at the points somewhat but I kinda think that if all 4 of them are showing correct firing display in the Strobo-Spark that you might be wiser to just use them as is and spend your money on having an original regular set of 4 T coils rebuilt. I don't honestly think you will get much improvement in your coils performance but your car will probably run OK with the caps that are in there. One way to tell is to simply have your coil test guy "bridge" a correct type of .47uF capacitor across the coil mounting bolts to thus temporarily add that capacitor to the internal .18uF and see if it really makes much difference. I suspect it won't do anything too radically different. This way you can at least see what spending a lot of time and effort with new .47uF will net you. Yes the sum total of the capacitors will be oversize at .65uF but you can see if the spark waveform changes and what effect the change of capacitors will have. I kind of assumed in your original post that you didn't mean one was .017 but rather that the range was from .11 to .17 so I could be off base here if one was indeed .017uF. You can verify if these are the coils you have and what you might want to do. The secondary windings are very very thin on these coils and prone to breaking so I personally don't use them as rebuild candidates but your mileage may vary.


Top of pagePrevious messageNext messageBottom of page Link to this message  By tommy coffey on Monday, November 13, 2017 - 05:04 am:

These are coils that I found for sale. They have plastic cases. The price is good if I could "fix" them by just changing out the capacitors. How does one open and reclose the plastic cases?
John, yes I meant to type 0.11 to 0.17. Meaning one , the lowest, checked at 0.11 and one, the highest at 0.17, with the other two somewhere in between. My goal is to have a good set for my car and a good set of 4 spares. Currently I am running two borrowed coils. Thanks Lenny.


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