View single post by Judson Manning
 Posted: 04-15-2005 01:29 pm
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Judson Manning

Joined: 03-14-2005
Location: Atlanta, Georgia USA
Posts: 406

Pre-1974-1/2 cars have a physical resistor which looks like a small 1/2"x1/2"x2" white brick mounted next to your coil.  Later cars have a Nichrome wire built into the wiring harness which accomplishes the same thing.

Assuming you do have either a ballast or the Nichrome wire, it can be checked easily:  If you start your car and put a Volt Meter on the + side of the coil while it's running, you should find you ony have 9-10VDC instead of the expected 12-14VDC. 

The JH is actually wired such that full battery voltage is supplied to the coil when the starter is engaged (the extra wires on the coil and the starter).  This helps cold start-up.

Installing a Lucas 'sport coil' or other type of coil that has an integral resistor w/o removing the ballast resistor causes only about 7VDC to reach the coil.  Is it a problem?  For a bone-stock car running in perfect condition down to the Grocery it's not.  However, once you up the compression, open the plug gap, or require any real work from the engine, 7VDC won't be enough and you'll be plagued w/ missfires.