I searched the forum for oil overfill and read many posts on how to check the oil but none that said if on overfill caused any damage or just a mess as it leaks out? Does an overfill do any damage to the engine or seals?
I was told a long time ago to put one gallon of oil in at oil change and just make sure it stays no lower than the upper check petcock. I have been doing this for years without any problems.
Ronald - The oil level when filled properly should be between the two petcocks on the transmission oil pan. If you open up to the and it runs out, there's too much. If you open up the bottom and nine runs out, there's too little.
With the splash system, I'm sure there are time that the oil is abnormally high in some areas especially when going up or down hills. But if filled properly it's no concern.
Personally, I believe some put way too much thinking into the oil level. I just make sure I have a steady stream at the lower pet cock. When it gets to where it is a real weak stream, I add a quart. I've seen some folks say they fill until it runs out of the top pet cock every time they add oil, then they leave the pet cock open and let it quit dripping. I guess they are worried that those drops are going to overfill the crankcase. I do not believe this level of attention to detail is necessary. When I change oil, I put 4 quarts in it. There have been times that I knew I had oil above the lower pet cock, but was going to go on a long drive and wanted to be sure I didn't run low. On those occasions, I will open the top pet cock and fill until I see it start to run out. I will then close upper pet cock and go about my business.
My son and I were working in the garage this weekend and he suggested that we change the oil in the T.
I replied that it has an automatic self changing system.
He looked at me as if I was from another planet -- until I pointed to the small catch pan on the floor under the T and he said "I get it!"
BTW - I use the cheapest 10-40 I can find and add oil until it drips out of the top petcock.
Once I was in a hurry and over filled it.
It ran like crap until I lowered the level to the top petcock!
The T has a way of telling me what it likes and doesn't like.
For whatever reason (paranoia?) I was habitually overfilling the engine with oil using just the petcocks, so I rummaged around in my junk boxes and made this poor man's sight gage with a plastic elbow, a couple lengths of clear vinyl tubing, and a couple of spring clamps.
Now when I want to check the oil level I just open the bottom petcock and let the oil find its own level in the vertical tube, then close the petcock. Works great!
If the petcocks are installed with the handles down, you have to get under the car to turn them. If you install them like this,
you can use this to turn them without crawling under.
I have a period sight gauge similar to what Mr. Strange shows above. Looks
much like a sight gauge on a steam locomotive.
I've never used a sight gauge on my TT, but some time back the subject came up here on this forum. According to a couple of folks who posted there is some risk. It is possible for crud to accumulate in the sight gauge that can trap oil in the viewing tube thus showing an OK oil level when in reality the engine oil level is low. There were a couple of horror stories about ruining engines in this manner.
Beware of this kind. I've retired mine for three reasons.  It can break off or be made leaky by an encounter with some passing object, as in driving over a bit of sagebrush. Then, with no shutoff, your oil leaks out.  If the vent hole gets plugged, the oil in the gauge will stay up as the level in the pan goes down.  Without a good light behind the gauge, it's easy to mistake an empty one for a full one. This happened to me.
My sight gauge is just a piece of clear tubing. Open both petcocks to read it, then shut both so that if it gets knocked off no oil is lost.
Steve, I keep telling myself to re-orient the petcocks the next time I change the oil, but I keep forgetting, maybe next time!
Steve, I have an original petcock valve opening tool like the one in your post that came with my car when I bought it. The only difference is that mine has a flat, 1/2" long X 1/8" wide protrusion that comes down from the valve knob wrench portion. I was told by an old man that the protrusion was used to stick into the valves to unclog them of debris. Jim Patrick
From reading the posts it sounds like an overfill really doesn't do any damage. I asked because I think I may have overfilled and will check tonight. I didn't wait long enough for the oil to drain down before I added more. I noticed more oil leaking on the floor from the rear of the transmission and a few spots leading into the garage. I will warm it a bit, shut it down and open the top petcock and let it sit until the oil stops running and call it good.
I regularly dump in another 1/2 quart after it starts coming out of the top petcock, especially if I've got a long drive ahead of me. If you want to drain yours down to the top petcock, that would be o.k. too.
Most T's leak oil to some extent. If you can trace down your leak you may be able to stop/slow it.
The leak appeared to be from the pan seam toward the back. I thought I would try tightening the nuts/bolts on the pan and see if that helped.
I'll share something I just learned about oil level on my car. It has the sight glass like Steve shows and while in our neck of the woods I don't have too much of a chance getting in the sage brush, I share his concern.
I recently changed my oil and filled just about 3.5 quarts to get the level to show 7/8 of a glass- wanted it full but not in the unknown area above the glass. Started the engine (w/ outside oiler) and the level dropped as I expected and settled at about 1/3 glass. I'd tend to be more comfortable with a nice reserve rather than running a lower level where the oil is all splashed out.
If you over fill the oil it's temperature will rise. My 1924 touring oil temperature is usually 10 or more deg.below water temp. Over fill I have seen 320 deg. Not good for Babbitt !
I'm not doubting what you said, but why should some excess oil cause excess oil heat? I don't get it.
As is the case with Henry, I don't get it either. I suppose that if the crankcase were grossly overfilled it could cause problems, but a minor overfill should not. BTW - if my '27 touring is on a level surface, oil will just barely start to drip from the upper petcock as I finish adding the forth quart of oil.
"but why should some excess oil cause excess oil heat?"
I would suspect that the oil is picking up heat from the pistons.
A very knowledgable old timer told me that he used to put in an extra quart of oil if he was going to be driving up a lot of hills. Said he never had a problem because of the exrtra oil.
If the oil is over filled it splashes more on the inside of the pistons transferring the heat to the oil. The surface aria of the pan is what cools the oil that never changes.
Watching oil temperature you can see it rise with a tail wind ,drop with a head wind, and be in between with a side wind. I can also see when I am getting low on oil by monitoring it's temperature.
P.S. I used to run excess oil until 2008 when I installed a temperature sensor for the oil.
Very interesting Dean. I would never have thought of it that way. Thanks!