MTFCA Forum

There is a small amount of oil puddling at the spark plugs on my '23 Touring. Cylinder head is the high compression Z-head. When the car is running I see it bubbling slightly, not very much. If you've ever seen the movie Giant with James Dean and a host of other big stars, there's a scene where he hits a gusher and just before it turns into a geyser of oil there is some bubbling. It's like that but maybe not as extreme. I would prefer there to be no bubbling but if it is not serious I'd just as soon leave it alone. I have removed all plugs to address an intermittent miss and they all have quite a bit of carbon, with one of them having a large deposit of gunk on the bend where it turns 90 degrees to meet the electrode.

Anyway, I got a little off-topic. About that oil--anyone else experience this? This is a fairly recent car for me, just in the "getting to know you" phase. Overall it's a good runner. Thanks for any words you may have about this. Gerrit

Just a sign of an engine that has plenty of miles up on it, if you don't have any clutch dragging issues or freezing weather, then run a heavier oil like 20w50

Aluminum head should have some aluminum anti seize on the spark plug threads. You will be able to tighten better & threads wont gall. As far as excess oil in the cylinders, thats a separate problem.

Bubbling oil around spark plugs ? Cut some aluminum foil about 1/2”-5/8” to wrap around plug threads.

Sounds like worn out rings where oil is getting past the rings and into the cylinders. A compression test will reveal some facts.

Are you seeing oil smoke out of the exhaust? If not, I wouldn't worry about it. I have mostly thought that this kind of leakage is more of a mixture of unburned gas and carbon than it is oil. Just put some sealant on the threads.

Too much oil in the pan will cause excessive oil to get into the combustion chambers, especially when idling. If your engine has an auxilliary oil line installed, that can also cause over-oiling in normal driving. Ford recommended running the oil level halfway between the upper and lower test cocks on the oil pan. Idling a Model T engine for more than a short time with the front of the car pointed downhill can flood the front of the rod trough with oil, which can lead to excess oil getting into combustion chambers. Use care when installing and tightening spark plugs in any aluminum head. Another possible source of excess oil in the combustion chambers is excess valve stem clearance. A number of T engines have modifications which may contribute to oil consumption, such as rod dippers, auxilliary oilers, and probably others.

I am going to ask a question, and then give a few suggestions.
Is the cylinder which has the bubbling oil the same one from which you pulled the spark plug with "gunk". and is it the same cylinder which was misfiring"? If so , what you see bubbling might be unburnt fuel.

I agree with George about putting foil around the threads.
Do not put sealer, but use aluminum anti seize on the threads.
The expansion of aluminum is greater than steel. So after you tighten the spark plugs, warm up the engine and then check to see if you can tighten them a bit more after the aluminum expands. Yes that could be the case. My son had a Corvair which has aluminum heads. Someone told him to pour some water down the carburetors while the engine was running to get the carbon out. Well! Guess what happened? The steel valve seats came out of the aluminum head! This is the same thing which is happening when you warm up the T engine. Only no valves in the head. But it does expand.

You don't want to use too stiff oil, because of the gravity flow lubrication. It needs to flow freely through the oil line. If you continue to have misfiring and if you have to frequently add oil, it might be time to rebuild the engine.
Norm

Norman Kling wrote: ↑

Wed Feb 09, 2022 8:44 pm

I am going to ask a question, and then give a few suggestions.
Is the cylinder which has the bubbling oil the same one from which you pulled the spark plug with "gunk". and is it the same cylinder which was misfiring"? If so , what you see bubbling might be unburnt fuel.

I agree with George about putting foil around the threads.
Do not put sealer, but use aluminum anti seize on the threads.
The expansion of aluminum is greater than steel. So after you tighten the spark plugs, warm up the engine and then check to see if you can tighten them a bit more after the aluminum expands. Yes that could be the case. My son had a Corvair which has aluminum heads. Someone told him to pour some water down the carburetors while the engine was running to get the carbon out. Well! Guess what happened? The steel valve seats came out of the aluminum head! This is the same thing which is happening when you warm up the T engine. Only no valves in the head. But it does expand.

You don't want to use too stiff oil, because of the gravity flow lubrication. It needs to flow freely through the oil line. If you continue to have misfiring and if you have to frequently add oil, it might be time to rebuild the engine.
Norm

Norm and others,

Thanks for the replies. Since you asked the question about the gunk and which cylinder it came from--here's the best I can tell you. All cylinders are bubbling. For the misfire, I am just now trying to isolate it so I don't have an answer for that except I'd be surprised if the plug with a lot of crud on it were NOT misfiring.That's #3 BTW. I just pulled them this evening. With a good cleaning, they appear to be in good shape.

I am glad you brought up the subject of tightening the plugs. When I loosened them they all seemed incredibly tight. From my tire-changing experience on modern cars, I'd say right around 80-85 ft lbs. Should they be torqued that tight? I used a box socket wrench so I did not have a torque reading when I removed them. I could be overestimating how tight they were, just seemed extreme for an antique car.

I should have time tomorrow or definitely by Sunday to put the plugs back in, start the car and see where I am with the misfire. I see a rigid line on my engine and I suspect it may be an aftermarket oil line but I'm not sure. I'll check that as well because I want to know what it is. It looks too modern to be original equipment. Thanks again for all the replies and comments. I'll check back with any further info.

Gerrit

If you can see a pipe running from the back of the engine under the firewall area to the front lower corner of the engine, that is most likely an auxilliary oil line. They are a good thing to have, generally, especially if you drive fast or in hilly areas or have mods to increase speed and power, or all of the above. However, some types can cause over-oiling under some conditions, such as short trips and extended idling. Be sure your engine is not over-filled with oil. An over-rich fuel mixture can contribute to dirty plugs, oil dilution, and bubbling around plugs. Cold running, slow driving, short trips, too much oil in crankcase, and over-rich fuel mixture can all contribute to fouled plugs. Once a plug or plugs is fouled, that cylinder will tend to accumulate oil and soot due to frequent miss-firing and reduced opportunity to burn off contaminates. Ignition system problems can aslo lead to plug fouling.

Cleaning the plugs, checking and adjusting the oil level, and getting the car out on the road and running for 15-20 miles at 30-35 MPH may do it a world of good. Another thing to do is be sure you have fresh, clean fuel in the gas tank.

Gerrit ...... You may have to put a new set of spark plugs and that engine . After you take out the spark plugs, clean up the threads and do a comparison look at the thread height. If the threads have flat-looking threads , I would say that's the cause of your problem. Compression leakage. .... .,........... Threads on good plugs should have the sharp pointy appearance, and when properly installed will seal properly in the head. ....... Set the spark plug point Gap at 0.025" . The deposits you saw on the spark plugs are you, like others have said, could be from too much oil in the crankcase , and/or worn compression and oil rings on the Pistons.

I had some bubbling, most likely excess fuel. I used a small amount of pipe thread compound on the plugs and adjusted my carburetor. It is running great now.

Remember. Aluminum head, steel plugs. Anti seize will seal & protect head threads.

You didn't mention the brand of plugs you're using. A friend had a similar problem which disappeared when he put in Champions.

Oldav8tor wrote: ↑

Thu Feb 10, 2022 10:30 am

You didn't mention the brand of plugs you're using. A friend had a similar problem which disappeared when he put in Champions.

Excellent point Tim. Some plugs have threads that are not fully formed, which creates a poor seal.

Jerry, I agree ...... as in my post above... Regardless of the brand of plug, you have to check the threads on the plugs for a complete seal after installation.

Frothing at the plugs like a rabid dog. I think it just wants to get out and run.
Rich

Moxie26 wrote: ↑

Thu Feb 10, 2022 11:45 am

Jerry, I agree ...... as in my post above... Regardless of the brand of plug, you have to check the threads on the plugs for a complete seal after installation.

Sorry Bob, I missed your prevously mentioning the issue. Good advice should be stated twice!

After fixing the bubbling spark plug threads, the root cause of oil entering the combustion chamber still needs to be addressed. The cause might be engine oil level being too high or worn oil rings.

Art Mirtes

Too much oil, fuel-diluted oil, over-oiling due to auxillary oiler flooding troughs, bad rings, worn valve guides. Model T engines need 20W oil, or a 10-30 oil, or at least a multi-grade oil with a low first number, such as 10W, 20W. A rich mixture will also cause cylinder fouling/plug fouling, as will a spark plug that, for any reason, is not firing consistently. Check the EASY things FIRST. Assume nothing.

Jerry ......
I was in total agreement with your post. Thanks.

Just checking in to let you know I am reading the replies and really appreciate the ideas and suggestions. The plug brand is Autolite and they all match. I will stick with the current plugs while I troubleshoot some other things. The oil level is in fact a bit overfilled--my understanding is that it's supposed to be between the upper and lower marks and definitely not above the full mark. I have an aftermarket dipstick to check oil level, nice addition. I've cleaned and put the plugs back in, have not yet fired up the car. I will check back with anything new, thanks again. Gerrit

If you got oil bubbling in the sparking pug recess, then you must be pumping oil. If you are pumping oil, as a result of oil passing the rings via a vacuum, then you must be burning oil too. Consider the oil in the sparking plug recess as a reserve for when you run out of oil. Did you check your compression?

The presence of oil at the cylinder head recess for plugs only designates a non seal on the threads of a spark plug to the threads in the cylinder head which are tapered. The origin of the oil, either excessive oil in the crankcase or otherwise has nothing to do with the seal of the spark plug into the cylinder head.

With the after market dipstick, it should be attached to the bottom petcock. So open the top petcock and fill until the oil begins to run out then leave it open till it stops running. That is the full position. Now close the top petcock and check the dipstick. The oil level shown on the dipstick is the full position. If it differs from the marks on the dipstick, file a new mark at that point. That will be your new full mark.
Norm

Some good suggestions here. Especially the one about doing a compression test. Both wet and dry by the way. You’ll know nothing about your engines condition until you do it. Everything else is a guess and stop gap measures.

It was mentioned that the spark plugs are tapered, they are pipe threads and almost impossible to have a tight seal. Other model cars use the flat bottom type plugs that seal by bottoming out.
T plug threads can be re-machined to to fit a flat bottom plug or inserts are available to accommodate a conventional plug. My 26 bubbles all the time I believe it is inherent in the design.

None of my 5 T's bubble from the plugs - tighten them up !

My engine would accumulate a small amount of thick black goo at the front and rear plug. Both the front and rear plug showed more carbon deposition than the others. The engine would smoke some at hot idle, but at no other time, and showed little to no blowby at the oil filler. I wrapped the plug threads with Teflon tape which stopped the goo from accumulating, but the carbon deposition at the front and rear plug and some smoke at idle remained the same. The engine has a Texas T auxilliary oiler installed, and it is a tight engine that runs well. I began to think that the aux oiler might be over-oiling the engine. I cut out a couple of inches of the copper aux oil line and inserted a length of hose with another smaller piece of hose inside it to serve as a restrictor. The goo accumulation went away, and the smoke at idle was reduced almost to zero, even at extended idle. The plugs showed very little carbon accumulation. I increased the restiction slightly more by putting a length of wire inside the restrictor and the plugs all now run nice and clean and the engine does not smoke at all unless I idle it for several minutes with the front of the car pointing downhill. I could probably do away with that by removing the aux oiler, but I'd rather not lose the benefits of the oiler. The car is capable 50+ MPH, and probably needs the extra oil.

Altair wrote: ↑

Sun Feb 13, 2022 10:40 pm

It was mentioned that the spark plugs are tapered, they are pipe threads and almost impossible to have a tight seal.

Why would that be? Every pipe in my house, (water & gas), uses tapered pipe threads and they don't leak? It's just spark plugs that are not manufactured correctly.

Like most things on forums, this is getting way "over thought". Seal the threads, move on, enjoy the ride.

I think some modern plugs have poor quality threads, and most T heads probably have some wear of the plug threads. Many of these engines were run through the Depression and WWII and were using a lot of oil, necessitating frequent plug cleaning to conserve gasoline. A good tapered pipe thread joint won't leak significantly . I think most T heads leaked a little at the spark plugs unless the plugs were very tight, but normal combustion residue served to seal them off. If significant oil is present, that may not occur, and the oil mixes with soot to make the goo. T engines have low compression, and they will accumualte more soot and carbon than typical later engines in the same condition. High compression makes for thinner carbon deposits and more complete combustion under a broader range of operating conditions. Does anyone know what the cylinder peak combustion pressure at full throttle in a stock T engine would be? Overtightening plugs in a T head risks cracking the head and might lead to squeezing down the diameter of the threaded portion of the plug body. It may also affect the plug gap. A worn thread in the plug hole will allow the plug thread to bottom out withought tightening properly. An off-spec thread on the plug can do likewise. A good plug in a head in good condition will tighten properly with about 3 threads showing above the head.

Lean it out some, it sounds like its also running rich in addition to the other issues, then take it out for a good run and adjust the mixture on the road to see if it acts better afterwards.

Jerry VanOoteghem wrote: ↑

Mon Feb 14, 2022 12:38 pm

Altair wrote: ↑

Sun Feb 13, 2022 10:40 pm

It was mentioned that the spark plugs are tapered, they are pipe threads and almost impossible to have a tight seal.

Why would that be? Every pipe in my house, (water & gas), uses tapered pipe threads and they don't leak? It's just spark plugs that are not manufactured correctly.

Like most things on forums, this is getting way "over thought". Seal the threads, move on, enjoy the ride.

Pipe threads have a spiral leak path regardless of how tight they are. The ones in house plumbing have some sort of sealant or they WILL leak. The trick on the spark plug threads is finding a sealant that will handle the heat.

Thanks for all the replies and conversation. I've replaced the plugs after throughly cleaning them, ran the car but didn't drive it. They get the salt and brine trucks rolling at the mere mention of snow here in Maryland, otherwise I would have taken it out for a nice long drive. Engine is very smooth, probably didn't run it long enough to get any bubbling action but I'll monitor that when I hit the road. I should mention the plugs were incredibly tight when I removed them, way too much. torque in my opinion.

I've read all the comments about getting the car running smooth and carbon-free where the plugs are concerned. I am not experiencing a miss now, probably due to my replacing one coil that was tested as bad--and cleaning the plugs. I may still have to lean out the carb a bit as I am getting some black smoke from the exhaust. I'm really looking forward to hitting the road for a nice long run. Gerrit

mbowen wrote: ↑

Mon Feb 14, 2022 4:14 pm

Jerry VanOoteghem wrote: ↑

Mon Feb 14, 2022 12:38 pm

Altair wrote: ↑

Sun Feb 13, 2022 10:40 pm

It was mentioned that the spark plugs are tapered, they are pipe threads and almost impossible to have a tight seal.

Why would that be? Every pipe in my house, (water & gas), uses tapered pipe threads and they don't leak? It's just spark plugs that are not manufactured correctly.

Like most things on forums, this is getting way "over thought". Seal the threads, move on, enjoy the ride.

Pipe threads have a spiral leak path regardless of how tight they are. The ones in house plumbing have some sort of sealant or they WILL leak. The trick on the spark plug threads is finding a sealant that will handle the heat.

Agreed!

Black smoke points to an over-rich condition. You might check to see that the choke plate is opening fully when the choke button is pushed in. Beyond that, you can usually lean out the mixture by turning the choke button to the right as the engine warms up. Ford recommended seating the adjustment needle GENTLY by turning the adjustment knob to the right until the needle just seats, then turning it back to the left about 1 turn. Most engines will run well when warm with the adjusted from 7/8 to a little over 1 turn off the seat.

With the use of pipe threads there are several factors to consider, temperature, pressure and products transmitted. There is a path around the threads to atmosphere however the path is very limited and only certain liquids will travel through. Water will not migrate past the threads where as gasoline will. I purchased a reproduction Model T gasoline fuel bowl that said "tested to 10 LBS water pressure", when gasoline was conveyed through the system with no pressure it leaked. In a T engine you have high heat and pressure. On my 26 I had tightened my plugs securely and it ran fine with no signs of any discomfort, one day I used the garden hose to wash the car and water migrated in to the spark plug bowels in the head and there was a quantity of bubbles from beneath the plugs. They would not tighten any further and it continues to run that way. Most, if not all other makes of cars and stationary engines used a form of parallel threads with a compression type washer to overcome the leaking issue with pipe threads. I have a1917 Fairbanks Hit and Miss engine that was designed with an igniter, no spark plug. There was an after market supplier to adapt a conventional spark plug. The adaptor casting was machined with a pipe thread with a male pipe adapter that is threaded with a male pipe thread and a female thread to fit a conventional spark plug. The male - female threaded pipe to spark plug adaptor is also fitted with a compliment of fiber washers to seal the pipe threads, obviously they were a problem in 1917.
The spark plug has a parallel thread and seals with a compression washer.

The problem with the early FB engines was usually the igniter more so than the plug. A number of Z engines had later type, rotary magnetos adapted to them, and some people ran them with the tapered plug adapter and any common spark plug that that available, which was often as not the NPT type used in Fords. Ignitors, high tension magnetos, and battery/coil arangements were all in common use. The high tension magnetos eventually displaced the other systems. If you have the tapered plug adapter and an old style head, you could choose to run the engine on a hot tube, igniter and low tension mag, igniter and battery with low tension coil, battery, spark plug, and buzz coil, or high tension mag and spark plug.