Coil / Resistor

Reply Subscribe

Thread Tools

Search this Thread

Oct 19, 2003 | 11:30 AM

shft22

Thread Starter

Racer

Joined: May 2003

Posts: 406

Likes: 5

From: Miami FL

Coil / Resistor

I’m upgrading my ignition on my 67, 427, and I have a question. I replaced the points with a Crane points conversion, I’m also replacing the coil with an MSD blaster 2, my question is do I need to use a resistor, for the coil. The crane ignitions suppose to receive 12 volts, and it says to use the resistor for the stock coil, but the coil is not stock and according to MSD it can handle 12 volts. So should I use a ballast resistor for the coil, or can it be connected directly to 12 volts. :grouphug:

Oct 19, 2003 | 03:38 PM

JohnZ

Team Owner

Joined: Oct 2000

Posts: 38,897

Likes: 1,926

From: Washington Michigan

Re: Coil / Resistor (shft22)

Call the MSD Tech Line and ask; there may be a difference between what it was "designed for" vs. "what it will handle"; what do the MSD instructions say? :thumbs:

Oct 19, 2003 | 04:21 PM

shft22

Thread Starter

Racer

Joined: May 2003

Posts: 406

Likes: 5

From: Miami FL

Re: Coil / Resistor (JohnZ)

I called the MSD Tech Line, they say to connected without a resistor, that it can handle the 12volts. I’m looking for real life experiences, what are people here doing.

Oct 19, 2003 | 08:30 PM

2 Ag R8Cs

Race Director

Joined: Mar 2002

Posts: 14,611

Likes: 3

From: Retired Suffolk County Police Dept NY South Carolina

Re: Coil / Resistor (shft22)

I can’t give you an answer but I can tell you what little I do know about older starting systems. Back in the early days distributors ran on less than 12 volts. My memory isn’t that good but I think they ran on 9 or 10 volts. But in order to insure better starts they resistor was bypassed on start of to give 12 volts to the coil. This system gave 12 volts for easier starts, but dropped the voltage down during normal running. I think the lower voltage was used for longer spark plug life but I am not sure. My guess is they want a steady 12 volts for a hotter spark because the newer plugs can hold up better to the higher voltage. This is just a guess on my part but it seems like the most logical reason to me. I am sure someone will correct me if I am wrong.

Oct 20, 2003 | 11:36 AM

JohnZ

Team Owner

Joined: Oct 2000

Posts: 38,897

Likes: 1,926

From: Washington Michigan

Re: Coil / Resistor (2 Ag R8Cs)

The reduced current provided by the ballast resistor (replaced by a resistance wire in the harness after '67) was for the stock coil, so it would only see 7-8 volts at the primary winding in normal operation; this was done to reduce the current across the points for longer point life. Prior to '63, the resistor was about 0.3 ohms, and it was changed to 1.6-1.8 ohms in mid-'63 and '64 to reduce coil primary voltage further due to customer complaints of point-burning. :thumbs:

Oct 20, 2003 | 12:14 PM

2 Ag R8Cs

Race Director

Joined: Mar 2002

Posts: 14,611

Likes: 3

From: Retired Suffolk County Police Dept NY South Carolina

Re: Coil / Resistor (JohnZ)

Quote:

Thanks I knew they reduced the voltage after the car started but I didn't know why. It makes sense that if they don't have anymore points to wear out there is no longer a need to drop the voltage. :thumbs:

Oct 20, 2003 | 02:14 PM

shft22

Thread Starter

Racer

Joined: May 2003

Posts: 406

Likes: 5

From: Miami FL

Re: Coil / Resistor (2 Ag R8Cs)

So, to understand what you guys are saying, the resistor was used to protect the points, not the coil. So I should be able to feed 12 volts to the new coil without any problems. :hurray:

Oct 21, 2003 | 01:33 PM

JohnZ

Team Owner

Joined: Oct 2000

Posts: 38,897

Likes: 1,926

From: Washington Michigan

Re: Coil / Resistor (shft22)

A stock coil will "fry" with 12 volts, but apparently the MSD coil is designed for 12 volts, so the coil won't be a problem. Points may need more frequent replacement with the MSD coil. :thumbs: