Inliners International Forums General Discussion Electrical ignition resistor.

i am currently doing a cab of restoration on an '55 1st chevy 3100. I did put in a 261 out of a Canadian Pontiac. Now that i have finnished the mechanical part of the engine rebuild and got it running reasonably, i was wondering if my ignition is set up right?
I did put in new points and a condenser, new plugs and since i am converting the truck to 12 v a 12 coil.

i read about instaling a ignition resistor when converting to 12 v. Why should i do that isnt my 12v coil enough? And people are also talking about a wire between the side terminal on the starter switch and the coil.

i am just trying to undestand why i should or should not do these things.

Thanks,

Dennis.

Greetings . . .

I believe the resistor is placed in the circuit for point life. 12 volts is hard on contact points due to excessive arc which leads to erosion. I think the resistor steps the voltage down to 9 or 8.

You should check the specs on the coil you've fitted - I think most have the ballast resistor built in. If so there is nothing to do.

regards,
Keith

Dear Dennis;

Kieth is correct in part.

It does add to point life by reducing the coil imput voltage (run) to about 6.8V.

When starting the coil should get a full 12V. This compensates for the voltage drop at the battery when the starter is activated.

To connect this you'll find a terminal on the starter switch/solenoid that is only 'hot' in the start mode. Connect this to the coil by-passing the resistor.

If your 55 (foor start)doesn't have one, use one off a 57.

This was standard on all Chevrolet 6 (55-62) 12V systems. Check Motors Manual for diagram.

Good luck,

Just because a coil is for a 12volt system it does not mean that it is design to operate on 12 volts continously. The step down resistor is put there to reduce the operating voltage to the manufactures specification, there by extending the life of the coil.As John has suggested-- Adding a wire( Factory on most cars) that allows straight system voltage to the coil will help increase the spark for starting and will not damage the coil since it is only momentary. The "Condenser" is the part that keeps the points from burning by absorbing the EMF ( arc) voltage. It stores this voltage until the points close again and it releases the stored voltage to help the coil saturation.
If a person is have trouble with points burning then the condenser may be considered defective and needs to be replaced. If replacing the condenser with the specified condneser does not correct the problem, then the condenser should be replaced with a condenser with a higher MFD rating. A good parts man can give you these ratings. Although in the old days several different ones of different values were stocked, you may be able to order them if you are buying brand names like Delco,Standard/blue streak,Mallory.I think the stock 6 banger condenser is about 6MFD and the one I use is for a V8 chevy motor and is rated 9MFD.Using a larger capacity condenser will extend the point life of drasticly. Paul

Dear Paul;

I think the resistor/coil concept faded away & they (GM) just wound the primary heaver. Then the Government made HEI so It's all moot today.

Some Jap cars use the resistor method I'm told.

I always use Mallory coils/condensers on the Hot Rod stuff, never a problem.

The resistor concept is no longer used on HEI and Similar systems because they do not use "Oil Filled" coils.Some of the Prestolite and Motorcraft systems that use "Oil Filled" coils still use resistor but it is incorporated in the Coil it's self or the Control Module. Accel,MSD,and Mallory still have coils availble that are "oil Filled" and all the ones I have used still require an external Resistor unless they are being used with one of thier control boxes. Away maybe this will help clarify some of the " Spooky Stuff" for the newer guys...Paul

Thanks Paul and John;

I ordered a resistor yesterday to keep my new points alive.
it's great info i just keep learning every day.
As a agricultural mechanic i tinker a lot on diesel engine's.
i had great fun rebuilding my 261. and i am trying to get my hands on a 292 out of a combine.
So i will have enough questions when i get that one.
Anyway thanks for the replies.

Dennis.

What is important is the current through the points. I don't believe that resistor has anything to do with oil filled coils or not.

The condenser has to be the right size, not bigger. The Motors manuals of the fifties have a good description of determining the correct size based on which of the points contacts is cratering. The condensor absorbs the energy in the primnary of the coil when the points are opened (the current in an inductor cannot change instantaneously). Since the secondary is not perfectly coupled to the primary, there is still enough energy in the secondary to fire the plug.

Dear Dennis;

Jayson is correct.

At highway speed the charging system voltage is between 13.6-14.2 which is far more that the ingnition requires. To reduce current flow, the voltage is lowered to 6.8 via the resistor.