13T - Fouled plugs

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Darin Hull
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13T - Fouled plugs

Post by Darin Hull » Sat Nov 28, 2020 3:11 pm

I had a fan pulley go bad. Took off the radiator, replaced the fan pulley, and knocked out a few other little projects/maintenance. I was redoing the timing so I took off the #1 spark plug... I was surprised to see it appeared fouled. Took off the #2 plus since I’ve heard the front spark plug can be the most fouled. #2 seemed fouled, also.

So, mixture. I’ve set my Holley carb per the instructions on the MTFCA encyclopedia site:

http://www.mtfca.com/encyclo/holley.pdf

I have to run rich to get the car to initially start and then can dial it down quickly. 13T runs about one and a half turns open. Car runs smooth... seems to have the power I need.

Reading previous forums on fouled plugs I ran across this one:

http://www.mtfca.com/discus/messages/29 ... 1191186168

It mentions motorcraft plugs and gap as potential issues. I have motorcraft plugs gapped at .030.

I’ll attach a pic of two of my plugs... would you consider this fouled? Or would this be acceptable?

Darin
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Last edited by Darin Hull on Sat Nov 28, 2020 5:31 pm, edited 3 times in total.


Jerry VanOoteghem
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Re: 13T - Fouled plugs

Post by Jerry VanOoteghem » Sat Nov 28, 2020 3:57 pm

If the car runs well and does everything you ask of it, then I would not consider that plug to be fouled. :)

You could try leaning it out a bit more perhaps. I usually lean it out till I notice the power going down a bit, with slower acceleration, then I richen it up from there till performance comes back.


Norman Kling
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Re: 13T - Fouled plugs

Post by Norman Kling » Sat Nov 28, 2020 4:04 pm

Your plug looks about right for one which has been used. The contacts are clean . If it were fouled it would be all carboned up including the gap. Does the engine run smoothly?
There are two things which can foul a plug. One is an excessively rich fuel mixture which produces black carbon. If the spark jumps down through the carbon to the ground instead of across the points at the top it would be fouled. The other reason for fouling is excessive oil leaking through the rings. That leaves a black oily carbon around the end of the plug. Even the inside of the cylinder head and top of the piston will have carbon on it after the engine has been run for a while. If you have access to a spark plug cleaner, you can clean the plugs and they will run fine.
Norm


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Darin Hull
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Re: 13T - Fouled plugs

Post by Darin Hull » Sat Nov 28, 2020 5:14 pm

I took out each plug and noticed the common result of the plugs looking progressively better the farther back ya go. I cleaned the plugs with a soft brush I usually use to clean carbon off my firearms. I found almost all the material appeared to be like a soot. Came off very easily with brushing. There were some small areas of a harder deposit which I was able to mostly get rid of with a fingernail. Rechecked gaps and put them all back in.

Jerry - Thank you for the “sniff test” way of looking a the issue. The 13T has been running just fine, acceleration and idling all seem well.

Norman - Yes, it seems to run smooth. Once again, I have nothing to compare it to because I’ve only been around this T... but I’d guess it runs just fine.

Thank you,
Darin

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TWrenn
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Re: 13T - Fouled plugs

Post by TWrenn » Sat Nov 28, 2020 7:48 pm

I agree it really doesn't look all that bad, the important parts seem clean. Here's my #1 plug off my '13 when I too was doing some routine maintenance two weeks ago.
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Bill Robinson
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Re: 13T - Fouled plugs

Post by Bill Robinson » Sat Nov 28, 2020 8:13 pm

Myself, I wouldn't call those plugs "fouled". "Sooted", maybe, but not "fouled". #'s 1 & 2 tend to collect soot more than 3 & 4 because they are at the front of the engine and tend to get the coolest water coming from the radiator, therefore don't burn the fuel as efficiently. I think what you are seeing is perfectly normal unless the sooting occurred in an hour or less.


Norman Kling
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Re: 13T - Fouled plugs

Post by Norman Kling » Sat Nov 28, 2020 8:52 pm

One other thing which could cause the plugs to soot up, would be engine running too cold. If you live in cold climate you might need to put something to cover part of the radiator when it is very cold. Another thing which could cause a T to run cold would be a water pump especially without a thermostat. And with the water pump the water would take the shortest route from the pump through the radiator and back to the pump. That route would be through the front of the engine. An interesting thing happened with my first Model T. When I bought it there was a water pump on it and one day we took a tour, in I Think, February. We went into the mountains where it is colder than down here in the foothills. We stopped for a break. I noticed many of the drivers standing in front of their radiators to keep warm. Mine was still cold!
Norm


Art Wilson
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Re: 13T - Fouled plugs

Post by Art Wilson » Sat Nov 28, 2020 11:03 pm

The real reason stock Model T's run rich on the front two cylinders.

The problem is due to the design of the carburetor and the shape of the intake manifold.

The carburetor supplies fuel at the bottom of the venturi in the form of a puddle.

The bottom side of the intake manifold is gently curved from the carburetor up to the front intake port. The top side basically follows the same curvature up to where it curves back to the rear intake port.

This gas puddle from the carburetor is sucked into the bottom area of the intake manifold, and while getting partially atomized, flows up to the front intake port. The leaner part of the mixture goes to the rear intake port.

I discovered this over 40 years ago when I smoothed the inside of an aluminum intake manifold in an attempt to get more horsepower. I could not get the engine to idle on all four cylinders. By varying the mixture I could get it to run on the front two or the rear two cylinders, but not both the front and the rear at the same time.

I put the stock iron manifold back on the car and it runs fine. The front two cylinders still run a bit rich as do most Model T's with stock intake systems.


Moxie26
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Re: 13T - Fouled plugs

Post by Moxie26 » Sun Nov 29, 2020 2:16 pm

Darren; it's your choice either get new plugs or clean the ones you have, and set the gap to 0.025" . Also be a little more attentive on your running fuel mixture after the engine warms up.


Topic author
Darin Hull
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Re: 13T - Fouled plugs

Post by Darin Hull » Mon Nov 30, 2020 5:23 am

Robert,

Why do you suggest .025? Is that for motorcraft plugs or T plugs in general?

Darin


ThreePedalTapDancer
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Re: 13T - Fouled plugs

Post by ThreePedalTapDancer » Mon Nov 30, 2020 7:12 am

I suppose fouling was a common problem, hence the development of all kinds of accessory gizmos that aid atomization of the fuel. Most of these gadgets look like a steel gasket with a fine mesh of swirling design cut in the center.

http://www.mtfca.com/discus/messages/17 ... 1301424727
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Moxie26
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Re: 13T - Fouled plugs

Post by Moxie26 » Sun Dec 06, 2020 3:02 pm

Darin : Gaping plugs at .025" puts less strain on the coils and engine will start and run better IMHO . Works for me on our '26's 6 volt battery/ignition supplied system. . Even years ago on our 1950 Buick, they specified a gap of .025" on the AC-46 plugs.... on a 6 volt system..... no problems there also.

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