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Old 10-29-2019, 07:44 AM   #1
History
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Default 4 Blackened Spark Plugs?

What would cause the plugs to become covered in black crap so fast? If you've read my " Zenith Troubles" thread you know that my plugs were at least part of my problem with the engine running correctly. After cleaning them the engine ran great for what little time I ran it. One thing I noticed as soon as it cranked was how quite it was after I cleaned the plugs versus before I cleaned them. The engine sounded like the back ground sound to a ships engine in a movie while idling. It was super quite after I cleaned the plugs.

I had the engine running maybe 15 minutes total. I did drive it on the hiway about a half a mile and noticed the engine missing as I was in third gear gaining speed. I returned to the shop and parked it and yesterday decided to look at the plugs again. They were already getting covered in the black crap. I've not driven it enough yet to know if it uses/burns oil. I looked into each cylinder and it was black but didn't look wet. The back two cylinders looked like there was more carbon than the fron two.

What do I need to check and what order?

Thanks in advance.
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Old 10-29-2019, 08:10 AM   #2
Patrick L.
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Default Re: 4 Blackened Spark Plugs?

Sounds as though it is running rich or there is a problem with the sparklers themselves.
What plugs are you using ? If you're still using the 3x then you may need hotter ones.
How is the carburetor being adjusted ? The low speed adjustment is air not fuel. Where is the GAV set ?
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Old 10-29-2019, 08:19 AM   #3
rocket1
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Default Re: 4 Blackened Spark Plugs?

I would take a compression check,60 to 70 lbs is great.
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Old 10-29-2019, 10:55 AM   #4
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Default Re: 4 Blackened Spark Plugs?

Is the GAV set mostly closed. I worked on a Roadster recently where the GAV was more than 2 rounds open and he had the same problem as the OP. Sounds like it is running way too rich.
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Old 10-29-2019, 01:11 PM   #5
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Default Re: 4 Blackened Spark Plugs?

I’ve not driven it enough to know where it’s happy spot is (gav). It doesn’t act like it’s running rich, smoking or anything. I will try to lean it out. Could it be the coil not throwing enough fire? Condenser or anything like that ?

What would I ask for as far as something to check the compression, size of adapter?

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Originally Posted by midgetracer View Post
Is the GAV set mostly closed. I worked on a Roadster recently where the GAV was more than 2 rounds open and he had the same problem as the OP. Sounds like it is running way too rich.
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Old 10-29-2019, 01:20 PM   #6
Purdy Swoft
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Default Re: 4 Blackened Spark Plugs?

A lot depends on the carburetor that is used .

If a model B Zenith carb is used , they should be run with the GAV completely closed after warm up .
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Old 10-29-2019, 03:44 PM   #7
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Default Re: 4 Blackened Spark Plugs?

For a comp gauge adaptor just order/use the base to a 3X plug. The suppliers carry them for a few dollars each.


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Old 10-29-2019, 03:50 PM   #8
don3527
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Default Re: 4 Blackened Spark Plugs?

Make sure you don't have one of the $125.00 mufflers, they have a baffle in them that is way too restrictive and can cause the plugs to soot up quickly. See if your muffler has mandrel bends or regular exhaust tubing bends, that's the easiest way to tell. You need a good muffler with the mandrel bends.
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Old 10-29-2019, 03:53 PM   #9
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Default Re: 4 Blackened Spark Plugs?

Many years ago I picked up a set of spark plugs at NAPA for our 1929. The counterman didn’t give me the correct plugs. They looked and fitted fine but they fouled within just a few miles. Not knowing my new plugs were the problem, I checked everything.

Finally went back and got a set of Champions W16. Has been running great every since.
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