The Ford Barn

jchochole · 05-03-2025, 09:12 AM

On my '34 Ford, I believe my left and right spark plug caps are not in correctly. What's the trick to being sure they line up properly for the rotor to fire the plug contacts?

Thanks,
Jim

mcgarrett · 05-03-2025, 09:21 AM

If you look closely inside the outer rim of each cap you will see a small tongue that aligns with a corresponding notch in the distributor body on each side. Insert the caps and rotate them until the notch aligns and you're there. When installed properly, the caps should have a slight tilt towards the rear and should fit snugly all the way around with no gaps.

Model51 · 05-03-2025, 09:22 AM

The caps only go on one way. The plate where the plug wires connect have tabs along the outer perimeter which align the cap to the plate and the plate to the distributor base. You need to rotate the cap and plate assembly until the tabs engage. It's easier to do than to describe.

jchochole · 05-03-2025, 09:39 AM

Thank you fellas, I appreciate that detail. I'll correct em today and see how it goes.

34fordy · 05-03-2025, 10:11 AM

Different years have different caps with locating notches in different places.

jchochole · 05-03-2025, 11:11 AM

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I actually have a '37 distributor so I did my best to eyeball and be sure that both the caps fit & the rotor brush passes immediately next to the plug spike.

I wanted to ask how close the two brass contacts need to be. After lining it all up, I still can't get spark through to my plugs. Darned mystery. I have juice going into the dizzy and both the pigtail and carbon button are seated properly.

WTF?

Lawrie · 05-03-2025, 03:30 PM

If you look in the service bulletins, there is a test rig you can make using a model T coil, then its an easy task to test all the high tension stuff on the bench,
Lawrie

jchochole · 05-03-2025, 05:36 PM

Mystery solved! Turns out the previous someone used the wrong caps which have the tooth in the wrong spot, a way different year. So, the correct ones are ordered and coming. My car would never have started and that's why my plugs were spanky clean- it never started for the previous owner as well.

Terry,OH · 05-04-2025, 06:23 AM

Ford Spec. on the gap between rotor and inner cap contacts for 37 to be 0.0125 to 0.0065"

38 coupe · 05-04-2025, 11:07 AM

Quote:

Originally Posted by jchochole

Mystery solved! Turns out the previous someone used the wrong caps which have the tooth in the wrong spot, a way different year. So, the correct ones are ordered and coming. My car would never have started and that's why my plugs were spanky clean- it never started for the previous owner as well.

A friend in the San Antonio club purchased a "good running, nice condition" 1936 Ford coupe. It ran, but not right. The car ended up at dad's place and I got the job of going through the distributor. In addition to the normal tired condition parts, the passenger side inner cap was the later style turned 90 degrees to proper. I don't know how it ran as well as it did, but I wasn't expecting to find that.

05-03-2025, 09:21 AM	#2
mcgarrett Senior Member Join Date: Dec 2013 Location: Corsicana, Texas Posts: 1,306	Re: How to tell if V8 Dist caps are on right? If you look closely inside the outer rim of each cap you will see a small tongue that aligns with a corresponding notch in the distributor body on each side. Insert the caps and rotate them until the notch aligns and you're there. When installed properly, the caps should have a slight tilt towards the rear and should fit snugly all the way around with no gaps.

05-03-2025, 09:22 AM	#3
Model51 Senior Member Join Date: May 2010 Location: Fairfax Station, VA Posts: 777	Re: How to tell if V8 Dist caps are on right? The caps only go on one way. The plate where the plug wires connect have tabs along the outer perimeter which align the cap to the plate and the plate to the distributor base. You need to rotate the cap and plate assembly until the tabs engage. It's easier to do than to describe. __________________ 1935 157" 1 1/2 ton stake truck undergoing full original restoration 1936 131 1/2" panel truck rescue preservation Author of the 1935-1936 Ford Model 51 V8 Truck book published by the Early Ford V8 Club of America

05-03-2025, 09:39 AM	#4
jchochole Senior Member Join Date: May 2010 Location: Oswego, IL Posts: 413	Re: How to tell if V8 Dist caps are on right? Thank you fellas, I appreciate that detail. I'll correct em today and see how it goes. __________________ "Whether you think you can, or think you can't- you're right." H. Ford

05-03-2025, 10:11 AM	#5
34fordy Senior Member Join Date: Dec 2014 Location: Fort dodge, Iowa Posts: 1,228	Re: How to tell if V8 Dist caps are on right? Different years have different caps with locating notches in different places.

05-03-2025, 03:30 PM	#7
Lawrie Senior Member Join Date: May 2010 Location: Qld, Australia Posts: 4,529	Re: How to tell if V8 Dist caps are on right? If you look in the service bulletins, there is a test rig you can make using a model T coil, then its an easy task to test all the high tension stuff on the bench, Lawrie

05-03-2025, 05:36 PM	#8
jchochole Senior Member Join Date: May 2010 Location: Oswego, IL Posts: 413	Re: How to tell if V8 Dist caps are on right? Mystery solved! Turns out the previous someone used the wrong caps which have the tooth in the wrong spot, a way different year. So, the correct ones are ordered and coming. My car would never have started and that's why my plugs were spanky clean- it never started for the previous owner as well. __________________ "Whether you think you can, or think you can't- you're right." H. Ford

05-04-2025, 06:23 AM	#9
Terry,OH Senior Member Join Date: May 2010 Posts: 5,187	Re: How to tell if V8 Dist caps are on right? Ford Spec. on the gap between rotor and inner cap contacts for 37 to be 0.0125 to 0.0065"