Go Back   The Ford Barn > General Discussion > Early V8 (1932-53)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 10-26-2015, 08:45 PM   #1
Old Henry
Senior Member
 
Old Henry's Avatar
 
Join Date: Oct 2010
Location: Orem, Utah
Posts: 5,762
Default Correct Coil Resistance

I have been chasing an intermittent stumbling of my engine when under load and have replaced or checked out all ignition components and am now to the coil. I got this diagram from some authoritative source and have always suggested it to others. Primary coil is in the range of the diagram. But when I just checked the resistance of my secondary coil in my stock 47 Ford coil that Skip Haney rebuilt I only get 6,130 ohms, not the 10-11,000 ohms per the diagram. Is that low enough to affect the spark or not? Is the coil bad and needs replaced or just marginal?

__________________
Prof. Henry (The Roaming Gnome)
"It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness
Old Henry is offline   Reply With Quote
Old 10-26-2015, 09:26 PM   #2
fourfords
Senior Member
 
fourfords's Avatar
 
Join Date: May 2010
Location: Lake Elsinore, CA.
Posts: 411
Default Re: Correct Coil Resistance

Call Skip.
fourfords is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 10-26-2015, 09:59 PM   #3
G.M.
Senior Member
 
Join Date: May 2010
Location: Florida and Penna.
Posts: 4,471
Default Re: Correct Coil Resistance

Quote:
Originally Posted by fourfords View Post
Call Skip.
You got it. Get the correct coil rebuilt and forget these abortions. G.M.
__________________
www.fordcollector.com
G.M. is offline   Reply With Quote
Old 10-26-2015, 11:03 PM   #4
Lawrie
Senior Member
 
Lawrie's Avatar
 
Join Date: May 2010
Location: Qld, Australia
Posts: 4,195
Default Re: Correct Coil Resistance

Henry, I chased a miss or skip as you call it on the 33 for ages,turned out to be two loose valve guides and those two let oil into the cyl and fouled the plugs ,ran like a train while burning along at 50mph but slow and speed up and the miss was there.
Lawrie
Lawrie is offline   Reply With Quote
Old 10-26-2015, 11:18 PM   #5
Old Henry
Senior Member
 
Old Henry's Avatar
 
Join Date: Oct 2010
Location: Orem, Utah
Posts: 5,762
Default Re: Correct Coil Resistance

So far I've replaced all of the spark plugs, the points, condenser, rotor, and coil resistor. All I can think of that's left is the coil so I'll call Skip tomorrow and see what he thinks. I'll also PM Bubbas Ignition since he hasn't commented to see what he thinks of the low resistance secondary coil.
__________________
Prof. Henry (The Roaming Gnome)
"It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness
Old Henry is offline   Reply With Quote
Old 10-27-2015, 06:13 AM   #6
Terry,OH
Senior Member
 
Terry,OH's Avatar
 
Join Date: May 2010
Posts: 4,725
Default Re: Correct Coil Resistance

Sponsored Links (Register now to hide all advertisements)
Using the resistance of the coil Sec./Pri. will give you the approx. turns ratio. For both of the pictured examples it is about 13,500/1 . If Skips coil has a primary resistance of 0.5 Ohm you wind up with 12,300/1 . With 3 to 4 volt input, that's an approx. max. output of about 35,000V should be hot enough for a flat head.
Terry,OH is offline   Reply With Quote
Old 10-27-2015, 09:00 AM   #7
Old Henry
Senior Member
 
Old Henry's Avatar
 
Join Date: Oct 2010
Location: Orem, Utah
Posts: 5,762
Default Re: Correct Coil Resistance

Quote:
Originally Posted by Terry,OH View Post
Using the resistance of the coil Sec./Pri. will give you the approx. turns ratio. For both of the pictured examples it is about 13,500/1 . If Skips coil has a primary resistance of 0.5 Ohm you wind up with 12,300/1 . With 3 to 4 volt input, that's an approx. max. output of about 35,000V should be hot enough for a flat head.
Thanks. Bubba also said it was OK. So, I'll put the coil back in and continue looking elsewhere. Sure hope I can fix it before my 5 day trip on the Pacific Coast Highway next week.
__________________
Prof. Henry (The Roaming Gnome)
"It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness
Old Henry is offline   Reply With Quote
Old 10-27-2015, 09:08 AM   #8
Bored&Stroked
Senior Member
 
Bored&Stroked's Avatar
 
Join Date: Jan 2011
Location: Central Ohio
Posts: 5,011
Default Re: Correct Coil Resistance

Quote:
Originally Posted by G.M. View Post
You got it. Get the correct coil rebuilt and forget these abortions. G.M.
He got the coil from Skip in the first place.
Bored&Stroked is offline   Reply With Quote
Old 10-27-2015, 11:22 AM   #9
keith oh
Senior Member
 
keith oh's Avatar
 
Join Date: May 2010
Location: Millersport, central ohio
Posts: 668
Default Re: Correct Coil Resistance

Henry, Is this the same problem that you said leaving the hood open a bit while moving helped some?
keith oh is offline   Reply With Quote
Old 10-27-2015, 11:54 AM   #10
Old Henry
Senior Member
 
Old Henry's Avatar
 
Join Date: Oct 2010
Location: Orem, Utah
Posts: 5,762
Default Re: Correct Coil Resistance

Quote:
Originally Posted by keith oh View Post
Henry, Is this the same problem that you said leaving the hood open a bit while moving helped some?
Not really. It is a very minor form of that same problem that has plagued me for many months. It never stops me dead like the other problem did, just "flickers" or "stumbles" with a slight loss of power with hard acceleration or hill climb. And the worst part, of course, is that it is intermittent, not always, just once in a while. That's what makes it hard to diagnose and fix. Fortunately, most of the time when I'm just going along at any speed with normal throttle it is either hardly noticeable or doesn't exist.

Right now I'm driving with my timing light taped to the cowl so I can see its flashes through the windshield while I drive. The pickup is on the high tension wire coming out of the coil. I mainly did this to confirm that it is a spark problem, not a fuel problem. Sure enough, when the engine stumbles so does the light flashes.

__________________
Prof. Henry (The Roaming Gnome)
"It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness

Last edited by Old Henry; 10-27-2015 at 12:03 PM.
Old Henry is offline   Reply With Quote
Old 10-27-2015, 11:56 AM   #11
flatheadmurre
Senior Member
 
flatheadmurre's Avatar
 
Join Date: Apr 2015
Location: Sweden
Posts: 3,045
Default Re: Correct Coil Resistance

Quote:
Originally Posted by Terry,OH View Post
Using the resistance of the coil Sec./Pri. will give you the approx. turns ratio. For both of the pictured examples it is about 13,500/1 . If Skips coil has a primary resistance of 0.5 Ohm you wind up with 12,300/1 . With 3 to 4 volt input, that's an approx. max. output of about 35,000V should be hot enough for a flat head.
Pri/sec resistance doesnt give you the secondary voltage.
To be able to calculate output voltage you need the turns ration of the coil.
flatheadmurre is offline   Reply With Quote
Old 10-27-2015, 12:32 PM   #12
JSeery
Member Emeritus
 
JSeery's Avatar
 
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
Default Re: Correct Coil Resistance

Sounds like a loose wire or connection unless it is heat related. Or a vacuum / carb issue on the advance. Are you running the original vacuum only advance distributor?
JSeery is offline   Reply With Quote
Old 10-27-2015, 12:36 PM   #13
Old Henry
Senior Member
 
Old Henry's Avatar
 
Join Date: Oct 2010
Location: Orem, Utah
Posts: 5,762
Default Re: Correct Coil Resistance

Quote:
Originally Posted by JSeery View Post
Sounds like a loose wire or connection unless it is heat related. Or a vacuum / carb issue on the advance. Are you running the original vacuum only advance distributor?
Yes, stock distributor with centrifugal advance retarded by vacuum brake.

It certainly acts like a loose wire so I bypassed all wiring from the battery to the coil with a jumper from the battery to the coil. Didn't help.
__________________
Prof. Henry (The Roaming Gnome)
"It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness
Old Henry is offline   Reply With Quote
Old 10-27-2015, 02:02 PM   #14
FlatheadTed
Senior Member
 
FlatheadTed's Avatar
 
Join Date: May 2010
Location: Auckland
Posts: 4,691
Send a message via AIM to FlatheadTed
Default Re: Correct Coil Resistance

Check the spring loaded contact in the distributor if its a crab ,Ted
__________________
http://www.flatheadted.com


Flathead Ted brake Floaters ,
FlatheadTed is offline   Reply With Quote
Old 10-27-2015, 02:11 PM   #15
47COE
Senior Member
 
47COE's Avatar
 
Join Date: Apr 2011
Location: Oregon
Posts: 220
Default Re: Correct Coil Resistance

Quote:
Originally Posted by FlatheadTed View Post
Check the spring loaded contact in the distributor if its a crab ,Ted
That spring loaded contact was causing problems for me. Took it out and cleaned both halves of the connection.

Any '47 distributor (rabbit ears or crab) can have that problem.
47COE is offline   Reply With Quote
Old 10-27-2015, 02:19 PM   #16
Old Henry
Senior Member
 
Old Henry's Avatar
 
Join Date: Oct 2010
Location: Orem, Utah
Posts: 5,762
Default Re: Correct Coil Resistance

Quote:
Originally Posted by 47COE View Post
That spring loaded contact was causing problems for me. Took it out and cleaned both halves of the connection.

Any '47 distributor (rabbit ears or crab) can have that problem.
Quote:
Originally Posted by FlatheadTed View Post
Check the spring loaded contact in the distributor if its a crab ,Ted
I guess I'm not sure what spring y'all are talking about. Is it the strip spring that pushes the contact points together that I just replaced with the contact points? Isn't that the only spring in my distributor other than the one in the vacuum brake. This is the kind of distributor I have:

__________________
Prof. Henry (The Roaming Gnome)
"It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness

Last edited by Old Henry; 10-27-2015 at 06:53 PM.
Old Henry is offline   Reply With Quote
Old 10-27-2015, 02:25 PM   #17
Old Henry
Senior Member
 
Old Henry's Avatar
 
Join Date: Oct 2010
Location: Orem, Utah
Posts: 5,762
Default Re: Correct Coil Resistance

I think I figured out what you're talking about - the terminal that the wire from the coil connects to that has a spring loaded post that pushes against the points plate? If so, I can take that out and check it. I just removed that plate to replace my points and twisted the plate against that post to position it so hopefully it's OK. Distributor was built by Bubba a year or two ago.
__________________
Prof. Henry (The Roaming Gnome)
"It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness

Last edited by Old Henry; 02-28-2016 at 11:46 PM.
Old Henry is offline   Reply With Quote
Old 10-27-2015, 03:07 PM   #18
47COE
Senior Member
 
47COE's Avatar
 
Join Date: Apr 2011
Location: Oregon
Posts: 220
Default Re: Correct Coil Resistance

Yes, it is the post for the coil wire.

The only reason I found the problem is that it finally quit totally and I found it was open circuit between the coil wire screw and the inside brass plate.

Unscrew the post and then polish the end of the spring loaded pin with emery cloth. You can probably clean up the brass plate with emery cloth too without taking the distributor apart again.

My distributor was serviced by Bubba too and he cleans and checks that connection. But for some reason it still failed. See more (and Jim L.'s response) at:

https://www.fordbarn.com/forum/showth...52#post1152852
47COE is offline   Reply With Quote
Old 10-27-2015, 03:11 PM   #19
47COE
Senior Member
 
47COE's Avatar
 
Join Date: Apr 2011
Location: Oregon
Posts: 220
Default Re: Correct Coil Resistance

Looking at your distributor photo again, it looks like that pin is way off to one side and hardly making contact. Perhaps the photo is of a different distributor?
47COE is offline   Reply With Quote
Old 10-27-2015, 03:16 PM   #20
Old Henry
Senior Member
 
Old Henry's Avatar
 
Join Date: Oct 2010
Location: Orem, Utah
Posts: 5,762
Default Re: Correct Coil Resistance

Quote:
Originally Posted by 47COE View Post
Looking at your distributor photo again, it looks like that pin is way off to one side and hardly making contact. Perhaps the photo is of a different distributor?
That is an old photo of my original distributor that was worn out, not the one Jim built for me. It isn't even all together. You won't find the retaining ring around the points plate. That was the one Jim got in exchange for the one he sent me.
__________________
Prof. Henry (The Roaming Gnome)
"It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness
Old Henry is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 12:40 PM.