Oil in plug hole

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corkmodelt
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First Name: Noel
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Oil in plug hole

Post by corkmodelt » Thu Apr 04, 2019 1:10 pm

Hi Folks

Any ideas on why oil seems to be coming up threads in plugs after car being driven. Ive checked the plugs and they are tight

Regards

Noel

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Mark Nunn
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Re: Oil in plug hole

Post by Mark Nunn » Thu Apr 04, 2019 1:18 pm

Plugs may not be sealing even when tight. With the engine running, pour a small amount of water around each plug. If you see bubbles, the plugs are leaking.


Scott_Conger
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Re: Oil in plug hole

Post by Scott_Conger » Thu Apr 04, 2019 1:21 pm

And that is not a problem, other than you will eventually get some small amount of oil splatter on your firewall if you drive long distances at 25+ MPH or so.

Do not attempt to overtighten the plugs, and if you eventually decide to run a tap in the head when it's off, think long and hard about that, as your plug will permanently sit lower in the combustion chamber after any amount of cleanup is attempted. How low depends on you. There will be no guarantee that it will be leak free even when you're done. While NPT threads are technically supposed to seal dry, ask yourself why teflon tape and pipe dope exist, and how many times you have seen a natural gas or other pipe that did NOT have an additional sealant on it (answer is "never"). Some folks go to all lengths to seal spark plugs, and some ideas are worse or better than others. I prefer Henry's plan...don't worry about it.
Last edited by Scott_Conger on Thu Apr 04, 2019 1:31 pm, edited 1 time in total.
Scott Conger

Full Flow Float Valves - deliver fuel like Henry intended!


John kuehn
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Re: Oil in plug hole

Post by John kuehn » Thu Apr 04, 2019 1:30 pm

One way to get an idea if your T is starting to pump oil because of worn cylinders or bad rings is to pull all the plugs and carefully pull each piston close to the top.
Use a good light to check the top of the pistons one at a time to see if they look dark or oily.
The one you are concerned about should be to some extent. The others will tell the rest of the story about worn rings or not. While your at it the plugs could be dark or oily. That will tell you something also.
Another thing about worn engines is that a misfiring plug could be causing pumping in a particular cylinder.
Others will more ideas I’m sure.


Scott_Conger
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Re: Oil in plug hole

Post by Scott_Conger » Thu Apr 04, 2019 1:37 pm

Additionally, all T's as designed, pump oil...there is no oil control ring on the piston. The owner's manual recommends a quart of oil be added with every 10 gallons of gasoline purchased. It doesn't all leak on the ground. I tour a car that still sports cast iron pistons...the #4 plug sizzles oil when running and the other 3 are damp. None of them foul, and they are original plugs from the '20's. They all burn cleanly and I have not cleaned one since they were installed 7 years ago. They replaced "new" champion plugs which wouldn't run worth a darn in the car.
Scott Conger

Full Flow Float Valves - deliver fuel like Henry intended!


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corkmodelt
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Re: Oil in plug hole

Post by corkmodelt » Thu Apr 04, 2019 3:47 pm

Thanks for replies,

Are you saying that I should put thread tape on the plugs when I'm putting them in?

I must do a few jobs to the car in the next week or 2 as I have stripped threads in one bolt in the block also.


Scott_Conger
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Re: Oil in plug hole

Post by Scott_Conger » Thu Apr 04, 2019 4:14 pm

I'm saying: "Don't worry about it", as in, no tape.
As for stripped bolts, you need to make sure you do not break into the water jacket, and the best way to avoid that is to limit material removal. Helicoil products are very good and offer the least material removal to restore the threads. Ebay is a good source for a basic kit for minimal $$ outlay

Welcome to the world of "T's". They can be very adictive.
Scott Conger

Full Flow Float Valves - deliver fuel like Henry intended!


Topic author
corkmodelt
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Re: Oil in plug hole

Post by corkmodelt » Thu Apr 04, 2019 4:59 pm

Thanks for reply,

I havnt used Helicoils before do you think that this is what I need bolts are 7/16 unf am I correct?

https://www.ebay.co.uk/itm/7-16-UNF-V-C ... XQ-KRRiRmJ


Norman Kling
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Re: Oil in plug hole

Post by Norman Kling » Thu Apr 04, 2019 5:08 pm

I have had good results by wrapping some aluminum foil around the plug threads before I insert the plug. Seems to seal the leak and is a conductor for spark.
Norm


Allan
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Re: Oil in plug hole

Post by Allan » Sun Apr 07, 2019 6:13 am

Noel, the bolts are 7/16"UNC.

Allan from down under.


Adam
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Re: Oil in plug hole

Post by Adam » Sun Apr 07, 2019 10:22 am

To answer the original question; Most T spark plugs don’t seal 100%, but leakage generally isn’t visible on an engine in top condition unless there is something in the “plug well” like a little water, etc. If a “spark plug well” is filling up with oil, it is usually an indication of worn intake valve guides (too large a gap between intake valve stem and guide). You may or may not have noticeable smoke from the exhaust.

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