MTFCA Forum

I had to work on the transmission of my car, and decided to check the engine.
I checked the pistons, and cleaned the rings, without removing them. I opened the holes in the piston skirt.
The cylinders were looking good, and I did a rapid honing with a 3 stone tool.

Since restart, the engine is smoking and consuming oil like hell !
All cylinders are concerned. The spark plug are all oily.

A friend of mine told me never to clean the piston grooves and rings, unless changing them.
The question now is how far should I redo the work ?

I removed the head (OHC Montier), and the lower crankcase cover, and remove the pistons.
I measured the diameters of the cylinders, ½”, 2” and 3½” from top, in axial and transverse directions.
The diameters are ranging from 3.371” to 3.374” all together, with differences from 1.2 to 2.7 thou within the cylinders.
It seems that the engine block is quite good, never machined.

My pistons must be original Montier aluminum ones, with 2 steel frets.
Skirt diameter 3.740”, top diameter 3.724”.
The rings are metric size, 5mm high, 3mm thick. Questions :
What made the engine consuming oil through all cylinders ? Just cleaning the rings ? The car was not smoking before (I drove 200 miles since I get the car).
Can I go with just changing rings ?
Should I keep the same simple rectangular shape for all rings ?
Should I machine the groove to be sure of the shape, and possibly add a shim ?
Or just put new pistons, less authentic !

It's best not to disturb used piston rings unless you intend to replace them. I doubt if a very light honing did your engine any harm.

If you put reach ring back EXACTLY where it was on each piston before you took anything apart, and put each piston back exactly as before, it's possible the rings will re-seat if the engine is run for a few hours.

If the engine isn't making ugly noises, but only burning oil, I'd clean the spark plugs as needed and fill the engine with fresh 10W30 conventional oil and drive the car for a hundred miles or so, keeping a close check on the oil level and cleaning any fouled plugs as needed. Run the engine as if you were breaking in a new engine for the first 100 miles, then gradually increase speeds and loads as miles accumulate, avoiding any hard pulls.

You may find that the engine slowly begins to burn less oil, and it may quit burning oil altogether if you are lucky.

If it doesn't improve after a few hundred miles, it will probably need mechanical repair.

I assume that you did not make any other changes to the engine other than cleaning the pistons and rings. If you did, carefully consider whether that change or changes could lead to higher oil consumption.

what do you mean "opened the holes" on the pistons? Did you clean them or actually drill them?

what grit did you use to hone?

were the rings all offset from each other and none in line with the wristpin?

that is one very special car, and you need to proceed very carefully to maintain originality to the greatest extent possible (in my opinion). Hard to believe such a special that was running well, needed to be torn down and reworked like this, but that's a subject best left unaddressed.

I wish you luck in getting this back to the condition it started out in. If you are of a mind to, it would be nice to see the car itself, if you have any pictures. Not many on the Forum have seen such a car, much less even know of their existence.

Honing a bore and using old rings is a NO-NO, rings when running in conform to the bore and seat them to run the rest of their life as a seal, that is now undone, fit new rings and start over.

Rings typically have a top & bottom. A taper so that they scrape away the oil as opposed to pumping oil up. That taper could have been worn off by now, but maybe not. Were you carful to replace them exactly as they came out?
You made no mention of ring end gap when you put back together. That gap is quite small(around .018") A wide gap lessens compression & adds to oil getting by. As Scott eluded, ring ends should be staggered in relation to each other.
How well the rings fit in the piston groves is a consideration. There should be only enough extra width to allow the rings to expand & contract. There is no "shimming".
Consulting a good engine mechanic before & during would have been smart.

I am thinking new rings would be in order. Normally in a worn bore one buys .010" over size & grinds the ring gaps to the proper end gap clearance.

TXGOAT2 wrote: ↑

Sat Jul 08, 2023 5:14 pm

I assume that you did not make any other changes to the engine other than cleaning the pistons and rings. If you did, carefully consider whether that change or changes could lead to higher oil consumption.

I did make other changes : add oil slingers, add connecting rod oil dips, unclog the internal oil tube. For sure that is giving more oil to be pumped by the pistons. I put back the pistons, wrist pin towards camshaft, but looking at my pictures, I realized that it was mounted the other way around.

I drove already few hundred miles, nothing improved, and I consumed more than 5 liters of oil. Starting with 15W40 and adding 20W50.

Scott_Conger wrote: ↑

Sat Jul 08, 2023 5:17 pm

what do you mean "opened the holes" on the pistons? Did you clean them or actually drill them?

I cleaned them.
The ring were offset, but obvioulsly not in the same position. So statistically the ovale of the ring, did not fit the ovale of the cylinder. But it's less than 3 thou ovalization.
I did not remove the rings, so if they were tapered (which I doubt), it did not changed.
I did not measured the end gap. As you can see the ends are not square.

When I first measured the compression, I remember, all was OK. I do not know the history of that car, but for sure it was static in a museum in the last 15 years. Not sure it was much driven before.

Spending hours on the forum, I discovered this thread : "Smoky T". https://www.mtfca.com/discus/messages/2 ... 1336324100
At least, I am not the only one doing silly mistakes !
One interesting point : "so they put a rubber stopper in the neck, and it could not vent".
I have no breather cap, just an aluminum plug with o-ring.
My crankcase may be under pressure, which would also explain why my engine is very oily, as well as the hood inside.
That might be 90% of my problems !

I have no breather cap, just an aluminum plug with o-ring

And there remains a question as to why quarts and quarts of oil are going through this thing???

and now I'll ask: exactly what was the point of purchasing an extremely rare and historic vehicle from a museum, acknowledging that the engine ran fine, and then immediately tearing it down, "improving it" beyond what the famous builder built into it, and then executing work with no knowledge of how it goes back together?

you will be doing yourself and future generations (who may still have an opportunity to see this car in one piece) a favor if you get this car to someone who understands the technology and hope that no more damage occurs to this important vehicle

Compression test. See if the rings really didn’t reseat. Do this before tearing it down. You don’t know what’s really going on but as Kerry said a home and old rings in bad medicine.

Another possibility is to much oil in the cam cover. You said there is a OHC Montier head. There must be a oil pump to lube the cam. Possibility there was a orifice in a line that fell out flooding the valve guides.
Show a picture of the head/ motor please.

There is no cam cover in this version.
And no oil pump.
Scott, I appreciate your comment, but the car was not running fine.
The nice looking Schebler carburettor never worked. I started the engine with a standard NH one, and later find a Zenith HP4B.
The rear axle still had the babbit thrust washer, and very surprisingly, there was no 4th main bearing !!
The oil tube was totally clogged. The fan is not the right one, not mentioning the belt.
So definitely, I had to do something on this car.
I learn the hard way, and specialists are no so common and available in France.

Pierre wrote: ↑

Sun Jul 09, 2023 10:45 am

One interesting point : "so they put a rubber stopper in the neck, and it could not vent".
I have no breather cap, just an aluminum plug with o-ring.
My crankcase may be under pressure, which would also explain why my engine is very oily, as well as the hood inside.
That might be 90% of my problems !

There is no cam cover in this version.
............

No r oil breather cap and you suspect the engine may be under pressure, engine very oily as well as the hood inside &no cam cover over,
The rubber stopper was likely to keep unwanted guests rooming in the engine. You didn't mention if smoke was coming out of the tail pipe?
Doesn't sound like your burning oil but may be irrigating the roads

I have a set of .060 cast iron piston rings on classified for sale cheap. These are 1/4” rings, which is what yours looks like. You should have a look at them. Dan

I would remove the rod dippers and re-fit the rods. If you installed oil slingers on the flywheel, they may be moving too much oil. Also: Be sure you do not have too much oil in the crankcase, and be sure the crankcase is vented at least as well as a stock T.

If you have an external oil line in addition to the original internal oil line, you may be delivering too much oil to the engine.

If that modified engine has some kind of oil dam in the pan, it may be holding an excessively high oil level in the rod troughs.

A T engine with plain piston rings, or any other trpe of rings, has a limited ability to control the amount of oil reaching the combustion chambers. Modifications to increase oil delivery can easily overwhelm the oil control available, even with new rings.

An overhead valve setup can also lead to high oil consumption in some cases.

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