OT - Spark Plug Condition Question

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Model T Ford Forum: Forum 2016: OT - Spark Plug Condition Question
Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Eastern Nebraska on Tuesday, April 05, 2016 - 10:46 am:

What do you think of these plugs, relative "heat?" On our Ford six (K), the number 6 cylinder has always been too rich. The touring we had was the same, so the plugs were often black and sooty, eventually to the point of not firing. We put in spacers, and are now running #6 heat autolites in the 6 hole (two plugs).

How do these plugs look? The one without the plug journal is number six. The other two are from numbers 5 and 1.
Those two (5 & 1) have more gray than #1, but all have gray ash at the firing tips.

Thanks for your opinions,

Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange - Hillsboro, MO on Tuesday, April 05, 2016 - 11:13 am:

#6 still looks to me like it's running cooler than the others, keep going to a hotter plug in that cylinder a step or two at a time until it stays clean. You'll know you've gone to far if the car starts trying to diesel on hot shutdown.

Just my opinion. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Eastern Nebraska on Tuesday, April 05, 2016 - 11:32 am:

Mark,
Thanks. Are the other two where you want to be on appearance, or am I running a little lean?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange - Hillsboro, MO on Tuesday, April 05, 2016 - 11:56 am:

They look fine to me. Check the porcelain around the center electrode, if it is black or brown it's fine, if it's bone white and bubbled, it's too hot.

There are a lot of spark plug diagnosis diagrams on the web, but they are mostly for '60s V8 and later cars, I'm not sure they apply to older, lower compression engines.

Others may have more experienced eyes than me.

:-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Zibell, Huntsville, AL on Tuesday, April 05, 2016 - 04:42 pm:

Spark plug color is not an indication of spark plug heat range, but the temperature of the burning mix. White plugs would indicate a lean mix, and sooty too rich. If the mix is so lean you see black spots on the center porcelain, you have a real problem as that is metal deposits from the piston or other parts.

A hotter heat range plug should only be used if there is oil contamination. You want the electrode to get hotter to vapor off the oil. Also in high compression engines (not an issue with these engines) if the heat range of the plug is too hot, you may get detonation from the hot plug lighting the mix instead of the spark.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Eastern Nebraska on Tuesday, April 05, 2016 - 09:01 pm:

These are a few things I found online:

Babcox "Engine Builder:"

"Conversely, hot plugs are good for applications that operate mainly at low rpms. Because they have a longer insulator nose length, heat is transferred from the firing tip to the cooling system at slower pace. This keeps the spark plug temperature high, which allows the plug to self clean and prevent fouling."

" Air/fuel mixture modifications: Lean air/fuel mixtures raise the operating temperature, along with the plug tip temperature, possibly causing knock or pre-ignition. Use a colder heat range for leaner air/fuel mixtures. Rich air/fuel mixtures can cause the plug temperature to dip, allowing carbon deposits to build up on the tip. Use a hotter heat range for rich air/fuel mixtures"

This appears to say use hotter plugs for rich mixtures. For what ever reason, the number 6 cylinder on both Model K I have experience have a serious problem fouling the #6 cyl.

Currently I am using an Autolites number 66 plug. I went to three automotive stores today, and we found the Champion alternative, #405, but we're not able to find any hotter plug. Any suggestions?

Thanks,

Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Zibell, Huntsville, AL on Tuesday, April 05, 2016 - 10:32 pm:

Not sure if it will help you,, but I did find a heat range chart. http://www.sparkplugs.com/learning-center/article/225/heat-range-conversion-char t and this info. http://www.imps4ever.info/tech/engine/sparking-plugs-spark-plugs/spark-plugs.htm l Hopefully you can order a hotter plug for the cylinder that is fouling.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Eastern Nebraska on Tuesday, April 05, 2016 - 11:33 pm:

Thanks John. This isn't a very good pic, but this is what the #6 plug would look like before, completely fouled out. The Auto Lit is at least continueing to fire:


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Zibell, Huntsville, AL on Wednesday, April 06, 2016 - 02:24 pm:

I've been doing a little more thinking on this. On a 6 cylinder engine, 1 and 6 usually don't get a full fuel charge. If 1 isn't fouling and 6 is, I suspect oil fouling and not fuel fouling. I'd check the condition of the rings in 6 and the intake valve guide. A hotter heat range plug will help, but is would be a band aid approach to the real problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Wednesday, April 06, 2016 - 08:09 pm:

I was wondering about oil also. Generally, I think from your photos that you may be running a bit lean. I prefer to run on the slightly rich side in early car engines for valve burning reasons.
Oiling on early engines often suffers from an inconsistency in quantity of oil, especially in early "total loss" systems. Depending on the specifics of the system, they may run either more or less oil at higher or lower speeds, as well as more or less oil to some cylinders than to others.
A model T for example, tends to foul number one plug for two different reasons. Under most running conditions, number one runs colder than the other three because of the way water and air flow around it. This results in under-burning of fuel. But number one also tends to foul because of oil saturation because although in most conditions, the oil drains away faster at number one than the other three, and therefore runs on less oil. However. when you go downhill, the troughs under number one flood with oil which has no place to run out. The oil can became as much as a couple inches deep under number one, the splash SOAKS the cylinder, over-powers the rings, and burns in the cylinder fouling the plug.
Your K could have a similar situation with either the feed or the drainage which can be affected by both speed and incline in both positive and negative ways.
I don't think the plugs are the problem, or the solution. I do think I would richen the mixture a little bit. But that is me.
Drive carefully, and enjoy, W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Eastern Nebraska on Wednesday, April 06, 2016 - 08:33 pm:

Thanks for the input guys. I've used a temperature gun and checked cylinder jug temps, with no noticeable difference. As you can see above, no oil on any plugs, including #6. Furthermore, this engine has a fresh overhaul, with new pistons, rings and valves. The compression on 6 is identical to the other cylinders.

It just seems that the number 6 cyl runs rich, for no known rhyme or reason. The same thing has happened with our former K, and a friends K. The gentleman who owns our old K pulled the intake manifold off weeks after running it, and the manifold still had raw gas pooled by #6 intake valve.

Each of the three use a different car , a Buffalo, Holley and Schebler. My guess is the design simply results in a rich mixture being drawn into the back (6) cylinder.

I do know this hotter Autolite looks better and runs better than the pugs we've used. My guess is a little hotter plug will do even better.


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