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Old 10-28-2020, 07:06 AM   #1
35fordtn
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Default 2.5 ohm ignition resistor

Like a dummy Iíve lost my cheat sheet that listed a part# for a 2.5 ohm ignition resistor. Would anyone on here know it? MSD and Standard has/had one.
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Old 10-28-2020, 07:59 AM   #2
glennpm
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Default Re: 2.5 ohm ignition resistor

That's pretty high. You may have to add 2 resistors in series to get 2.5 ohms.

I just searched and could only find aluminum cased ones like this:

https://www.ebay.com/itm/Dale-RH-ser...cAAOSw3Z9atYF5


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Old 10-28-2020, 08:00 AM   #3
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Default Re: 2.5 ohm ignition resistor

JSeery posted this a short time ago.


https://www.fordbarn.com/forum/showp...0&postcount=15
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Old 10-28-2020, 08:09 AM   #4
Seth Swoboda
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Default Re: 2.5 ohm ignition resistor

I'm running the ICR35 on a 12 volt conversion. If I remember correctly, I have about 4 volts at the coil with this resistor.
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Old 10-28-2020, 08:25 AM   #5
whizzernick
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Default Re: 2.5 ohm ignition resistor

is this used on original coil for 12 v battery ?
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Old 10-28-2020, 09:21 AM   #6
Seth Swoboda
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Default Re: 2.5 ohm ignition resistor

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Quote:
Originally Posted by whizzernick View Post
is this used on original coil for 12 v battery ?
Yes. I'm running 12 volts and a skip rebuilt original coil.
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Old 10-28-2020, 09:42 AM   #7
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Default Re: 2.5 ohm ignition resistor

MSD has discontinued apparently the one I was hunting. A 1.8 ohm will work just fine.

However for the particular car a certain distributor and coil I am working on for a customer I had hoped for 2.5 ohms, to get the primary to 3.2 with a skip coil 12V. This car is going on a 14,000 mile essentially non stop trip next year and I was hoping to get "picky" on the primary resistance to ensure point life. I may just stack resistors.
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Old 10-28-2020, 01:07 PM   #8
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Default Re: 2.5 ohm ignition resistor

. I may just stack resistors.[/QUOTE]



If you stack two 1.25 ohm resistors is the end result 2.5 ohms resistance?
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Old 10-28-2020, 01:13 PM   #9
glennpm
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Default Re: 2.5 ohm ignition resistor

They have to be wired in series, end to end in a line, to get 2.5 ohms.
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Old 10-28-2020, 02:20 PM   #10
Seth Swoboda
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Default Re: 2.5 ohm ignition resistor

Quote:
Originally Posted by 35fordtn View Post
MSD has discontinued apparently the one I was hunting. A 1.8 ohm will work just fine.

However for the particular car a certain distributor and coil I am working on for a customer I had hoped for 2.5 ohms, to get the primary to 3.2 with a skip coil 12V. This car is going on a 14,000 mile essentially non stop trip next year and I was hoping to get "picky" on the primary resistance to ensure point life. I may just stack resistors.
I feel like this trip has the potential for a lot of fun. Wish it were me.
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Old 10-28-2020, 02:54 PM   #11
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Default Re: 2.5 ohm ignition resistor

I did cross check in my old napa buyers guide but nothing above 2.0 ohms ?????
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Old 10-28-2020, 07:26 PM   #12
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Default Re: 2.5 ohm ignition resistor

Quote:
Originally Posted by BUBBAS IGNITION View Post
I did cross check in my old napa buyers guide but nothing above 2.0 ohms ?????
Jim,
I was a MSD I had been using. The standard number was for a 1.8. MSD had at one time a 2.5 which I bought a handful of from a going out of business speed shop. Ran out and it appears they no longer exist. Typical me I am over thinking this.
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Old 10-28-2020, 08:52 PM   #13
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Default Re: 2.5 ohm ignition resistor

The resister is used to cut the 6.3 volts from the battery down
to minimum of 3.5 and max of 4.0 volts. This reduces the arc
at the points. The higher the voltage the bigger the arc. If you
get below 3.0 volts when you push the starter button the amp
draw from the starter pulls the coil voltage to low to make a
strong enough spark to fire. It will be a fuzzy little yellow ball.
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Old 10-29-2020, 02:56 AM   #14
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Default Re: 2.5 ohm ignition resistor

Check the voltage when cranking. If it is greater than 4 volts calculate what you need for a resistor to get you just under 4 volts. V = IR

Either a direct wire with or without this resistor will be wired directly from the starter to the + coil terminal. Once started the other wire to the + coil provides a reduced voltage for running.

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Old 10-29-2020, 09:48 AM   #15
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Default Re: 2.5 ohm ignition resistor

I dont know the ohms I just add a 65 mustang (ford ) resistor to the original 1933-34 ford resistor . The one on the inside of firewall ( the one next to fuse ) I have been doing this ( 12 volt battery ) - ground for over 40 years. same dist never a point problem. I do think a skip rebuilt original coil made to 12 volt is better.
What do you think.
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Old 10-29-2020, 12:08 PM   #16
35fordtn
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Default Re: 2.5 ohm ignition resistor

Quote:
Originally Posted by whizzernick View Post
I dont know the ohms I just add a 65 mustang (ford ) resistor to the original 1933-34 ford resistor . The one on the inside of firewall ( the one next to fuse ) I have been doing this ( 12 volt battery ) - ground for over 40 years. same dist never a point problem. I do think a skip rebuilt original coil made to 12 volt is better.
What do you think.
That is a 1.4 ohm and stacked with a .8-1.0 ohm original equates to pretty much what my math concludes is perfect for a 12V skip coil. (skips coils tend to be .7-.8 ohms whether 6 or 12 V)

Most people aren't driving these cars enough to even really matter by I am being nit picky..
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Old 10-30-2020, 03:31 AM   #17
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Default Re: 2.5 ohm ignition resistor

If running 12v on a 6v coil you could just stack a 50's ceramic voltage resistor first then run it through the stock resistor to coil. Early y blocks dizzys were 6 volts at 12v battery. The secondary stock resistor will knock it down to the comfortable 4v as designed. Just a thought anyway.


If you have a skip 12v coil, I don't see the problem.
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Old 10-30-2020, 04:34 AM   #18
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Default Re: 2.5 ohm ignition resistor

guess I missed all your travel postings.
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