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Old 01-03-2009, 03:02 AM
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Coil problems

Today I drove my '53 chevy around town a bit and then out in the rural area. Ran it up to 65mph and it just purred. Parked it up for about 20 mins and she fired right up again. However, as I let the clutch out it quit and would not restart. Took the plug lead off #1 and found no spark. So took the dizzy cap off and found spark at the points. But the coil was really hot. Called up a guy locally and he brought me an old used coil. We hooked that up and she fired right up. Went to take off and same thing again. I let it sit for a bit and tried to start it. It fired up but I had maybe 5 cylinders at best. Mainly 4 cylinders but it would sit there and idle ok. I had no alternative but to try and nurse it the 10 miles home. It coughed and popped under acceleration and ran real ugly. When I lifted off the gas peddle it farted and backfired and tried to quit. But it got me home. So I guess I need a new coil or is something else going on? 235ci blueflame converted to 12 volt through 6 volt wiring.
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Old 01-03-2009, 05:01 AM
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Transformed transformer?

An old coil causing problems is easy to believe, until you said you tried another coil. But even then, it's possible the second one is bad too, but it's more likely it's something else.

Check the points for a flat surface and adjustment/dwell. Replace the condenser and see what happens then.

Also check your timing just in case it slipped.
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Old 01-03-2009, 06:23 AM
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does it have a ballist resistor that could have burned out or cracked.
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Old 01-03-2009, 07:27 AM
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verify that at idle there is only 6-9V at the coil plus at idle...
(it proves the coil primary resistance and ballast resistor or resistance wire "total" of approx 3ohms are working correctly)
without about 3ohms, the arcing at the slow moving points burns them up fairly quick at idle....
above idle, once the alt amps kicks in it overpowers the resistor so there is 11V+ at the coil and the points contacts are now moving fast enough for no burning ...
(clean the the contacts with one of your wifes finger nail emory boards)

points shifted? changing the 28* dwell and contacts gap?

different coils are anywhere from .4ohm up to 2.0+ohms primary resistance....
look up the primary resistance rating for your particular coil and it is simple to test with a volt meter,,,see pic attached

my $.02:
a points system can be set up to work plenty good but a swap to a solid state module "points replacer" like a ($70?) Pertronix "I" does definitely gives a better ign spark intensity and spark duration and constant dwell to insure power output....
installed correctly they are reliable (3 year warrentee)....
if somehow it did die from a voltage spike, left the ign on motor off, (whatever) you can re-install the points system on the side of the road with a screw driver....

if you do want to stick with points, it can be wise to buy the better made parts from Mallory or others...

edit add:
the mechanical body of the dist has to be in good working condition (gear/bushings/centrifugal plate/springs/etc/etc) to deliver the only micro seconds long spark duration at the correct time!!!
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Old 01-03-2009, 01:39 PM
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Coil Problems

I'd have to agree with what the others said prior to my post, I am not a real big fan of point systems,my suggestion is to contact Tom Langdon from Langdon's Stovebolt. He sells a modified GM HEI distributor that works wonders on those old 235's. I got one of those from him as well as his holley webber progressive 2bbl carburetor. I loved that motor backed with a T5 from an S10.

It's well worth the money!
http://www.stoveboltengineco.com/aca...?productid=123

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Old 01-06-2009, 01:21 AM
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Update........

Well, I spent a couple of hours going over the ignition system and in this time tried four different coils. All of them old and used and none of them improved the situation. I meticulously went over everything with alot of patience and found a fracture in the coil wire from the neg. terminal to the distributor. So tidied that up and added some more modern connectors. When re-installing this wire I noticed it was quite loose at the connection in the dizzy with the points and the condenser can wire was about to drop out. Still making contact but only just. So changed the condenser while I was at it. Next I cleaned up all the posts top and bottom on the dizzy cap and also the rotor. Put in the old original coil and BINGO. Now all I need to do is to learn to make only one change at a time. Having made several changes all at once has cured the problem but I don't know for sure what it was.....However all is good.

Just one other point...Ballast resistor. I am pretty sure it is not passing through a resistor. I can't see one between the ignition switch and the positive coil terminal. But I could be wrong . Also don't most coils have written on them something like "to be used with external resistor". Perhaps you could elaborate this issue for me. My knowledge on this is a little short.
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Old 01-06-2009, 05:32 AM
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Ballast Resistor

Well this is where it gets fun. Some coils have an internal resistor. Some don't. Some are marked. Some aren't. You can also get resistor wire. Most of the time it's labeled, sometimes it's not, or it's worn off. You will have to see what you have. If your wiring to the coil from the firewall is cloth covered, chances are there isn't a resistor wire in there. (resistor wire is plastic or vinyl covered wire that has a calculated resistance to it, but looks like a normal wire. This was used in the 70's along with those fun things called fusible links) Find out what you have and add in what you need. IMHO, I would verify the wiring, change the coil to a new 12v coil with an internal resistor (that's what I did before the HEI conversion). Coils are cheap and no sense in trying to drive around with a questionable part. A tow home and a ruined trip will cost you more than the coil. (that's my 2 cents worth)
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Old 01-06-2009, 06:31 AM
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Quote:
Originally Posted by rossco
Well, I spent a couple of hours going over the ignition system and in this time tried four different coils. All of them old and used and none of them improved the situation. I meticulously went over everything with alot of patience and found a fracture in the coil wire from the neg. terminal to the distributor. So tidied that up and added some more modern connectors. When re-installing this wire I noticed it was quite loose at the connection in the dizzy with the points and the condenser can wire was about to drop out. Still making contact but only just. So changed the condenser while I was at it. Next I cleaned up all the posts top and bottom on the dizzy cap and also the rotor. Put in the old original coil and BINGO. Now all I need to do is to learn to make only one change at a time. Having made several changes all at once has cured the problem but I don't know for sure what it was.....However all is good.

Just one other point...Ballast resistor. I am pretty sure it is not passing through a resistor. I can't see one between the ignition switch and the positive coil terminal. But I could be wrong . Also don't most coils have written on them something like "to be used with external resistor". Perhaps you could elaborate this issue for me. My knowledge on this is a little short.
Check the voltage at the + side of the coil when the ignition is in the run position. If you have battery voltage you will need a balast resistor or resistor wire. The excessive voltage will cause the coil to run hot and will quickly burn the points up.
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Old 01-06-2009, 11:09 AM
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(to clarify Chet's post abit?)
if you have "full" batt volts (12V) with the key on at the coil plus you don't have a ballast resistor or resistor wire in the dash harness...
it was a 6V system so it's not likely at all that there is any resistance in the circuit....
(the original full 6V supply is about the minumum that points can work)

the "external ballast resistor required for points" is telling you that particular 12V coil "does" have a very low primary resistance built into it (anywhere from only .4ohm to about .8ohm which is fine for solid state)
not hard to find the designed primary ohms resistance of any specific coil on the web with gooogle....

a points system is engineered to have a long happy life operating with about 11-12V max and only roughly about 2-3A at the coil making a relatively long duration 10-12Kv spark with a .032 plug gap...
that's only about 36 watts supply into the coil...
(the ballast resistor and coil resistance total together keeps it in that engineered operating range)

there are only a few milliseconds available for the coil to charge and only microseconds of actual spark event....

so for points to make a "blue flame" (joules) hot spark intensity for about 200 microseconds the parts have to be a compatible operating matched set due to such a limited Watts supply....
(including the high ohms carbon plug wires which forces the coil to charge higher Kv to be able to jump the small gap)....

??????
for many many years Chrysler cars had a external ceramic 1.5ohms ballast resistor like the one circled in this pic' attached...
your local parts stores might carry it????
(about $10?, they are white, that one is painted)

read the coil ohms primary resistance with a meter based on the diagram to know what the coil primary is going to add to the ceramic 1.5ohms resistance....

way over simplified example/illustration only for the "idea":

Volts/total ohms resistance=amps to burn up the points

12V/ .8ohms primary resistance "performance" coil only=15amps of arcing heat at the points!!!
12V/1.5ohms ballast resistor +.8ohm coil=5.2 amps
12V/1.5ohms +1.5ohm coil =4amps=generic brand new points ballpark (so it will have hopefully 2-3 amps with pitted and burned points resistance added later down the road)

better to read the actual volts for 9V pratical max while running at idle because the alt may have kicked in and raised the volts to 14+ on the ign wire (to get a idea of expected points life)....
14V/3 ohms total=4.6amps...
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Last edited by red65mustang; 01-06-2009 at 11:19 AM.
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Old 01-09-2009, 11:32 PM
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bad condensor.
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