MTFCA Forum

Good Afternoon Forum Chums,

Gonna ask a couple of what I hope won’t be perceived as dumb questions? In between flying my trips I’ve been doing what I term as an engine refresh on my 27 Tudor.
Won’t bore you with all the numbers, but The Pistons and bores mic-ed up extremely well, nothing is out of round…….piston to bore wall is clearance is 3 thousandths….which I thought was astounding considering the age…..Pistons all stamped “Ford Standard”…..ditto rings on top “Ford”….I suspect could be original!

Background complete….now the questions.

First question……all the rings are worn, what I think considerably, on the ring gap side…(see picture)….never saw that before….done many rebuilds….but this is my first T…… he has anyone seen this before?……. any idea as to why?…..ordered new!

Second….the pistons all have punch marks on the top…..either 2 or 3…not 1-4 to mark position….any idea of what someone may have been trying to document?…..I’m stumped

Many Thanks
Cheers,
Ed

If the pistons are original, which seems likley, the numbers stamped on them may refer to their weight. I think it would be considered normal to see wear on the portions of a stock T ring nearest the gap, since they tend to spring open at the gap, and also because normal blowby at the gap may cause increased heating and diminished lubrication at that point.

The piston punch marks could be from an older rebuild and someone used some good used pistons. Are the cylinders ID still std pretty much the same for all 4 but larger then the std. 3.75 ?

Depending on how worn off the tops are you might still find STD on the top of original pistons by carefully cleaning the piston top. Or you might find the oversize dia. also if they were changed. All mechanics don’t use the same procedures when putting punch marks on engine parts so be prepared when you disassemble engines that are close to 100 years old.

They all say Standard clearly on top

I misread about the numbers. The punch marks might refer to weight, position, or who knows what. When I was a kid, the junk pile had T parts in it, with a scattering of rings and pieces of rings. It was common to see wear like the ring in the picture shows. If the pistons and bores are OK, check for wear in the ring grooves of the pistons. Excess wear in the ring grooves, or "stepped" grooves, can ruin an otherwise good ring job.

Brilliant Sir…..not handy to the specs right now…on the road… do you have any idea how many thousands is allowable on side clearance for the rings and the grooves?

Are you assuming the ring gap is to wide by what you see from the loose ring sitting on the bench?
Thats not how gap is determined. With the loose ring squarely in the cylinder, you use a feeler gauge for a reading.

.003 piston clearance in an old motor is too good to be true. That would indicate the motor has near no miles on it.
Standard iron pistons! Unbelievable. Was the motor sleeved back up to standard.

To each his own but since the pistons are std. and the bores aren’t really worn I would buy a set of std rings and put them it. But that’s me. Others might want to install a set of std. aluminum pistons. You will get all kinds of advice about this! The original pistons probably arent not worn that much. You probably have a low mileage engine. And that’s a plus.++++++++++++++!

I would install a new set of rings. Check the valves and and bearing clearances. It will run just fine for years of driven senseably

Art Mirtes

The punch marks on the pistons were to keep track of what cylinders they came out of, so that they could go back into the same bores.

Do a light hone on the bores prior to installing new rings or the rings most likely will not seat.

Here’s a good earlier post about installing new rings and the possibility of honing the cylinders. Not trying to resize the cylinder but just cleaning them up or deglazing. GOOD INFORMATION about the pros and cons about what to do when re ringing a T engine.

https://www.mtfca.com/discus/messages/3 ... 1377361579

and to Jerry's advice...use the type of hone and the GRIT that the ring mfg. recommends...a more important thing than people sometimes realize.

generally speaking, FLEX_HONE by Brush Research is my go-to product

Ring groove clearance should be .001 to 002. If the lower ring groove has oil drain holes in it, they should all be clear, but not drilled oversize. See Ford service book for specs and procedures.

Thanks Jerry….but the punch marks are not to note position……not numbered 1234….but 2332…. it’s what I initially had thought until I saw that I didn’t have sequential numbers…..good info about honing….I was planing on doing that!

One more thing to check would be to put the ring in the cylinder squarely near the bottom and measure the gap. Then move toward the top and gap should be near the same. This will measure taper of the cylinder.
Norm

All good information here so far. I am surprised that no-one has mentioned this so far though. Since you have the engine open and are working with the pistons, also check the valves to see if it still has the original two piece valves. If it does, replace them at this time. You can get standard sized T valves from the vendors. The two piece valves sometimes come apart and become actually two pieces again. Bad things happen when that occurs.

What do you plan to do with the car?

If you expect to drive it often at open road speeds, I suggest replacing the iron pistons with aluminum pistons and modern rings. Doing so will reduce engine vibration, improve performance, and give better oil control and longer ring life while reducing bearing loads due to inertia forces.

The iron pistons, if they are in good condition, will give good service at speeds up to about 30 -35 MPH in a car. Original type Model T rings cannot provide several functional advantages that modern style rings offer, such as longer life, lower oil consumption, reduced carbon deposition, better compression, and lower friction.

I would keep the iron pistons if they are in good condition, or sell them to someone who wants original-type pistons.

Flyingpiper59 wrote: ↑

Tue Feb 28, 2023 9:35 pm

Thanks Jerry….but the punch marks are not to note position……not numbered 1234….but 2332…. it’s what I initially had thought until I saw that I didn’t have sequential numbers…..good info about honing….I was planing on doing that!

Why did you have to throw a wrench into my well thought out theory?

Okay, well maybe it really is to sort out weights, as others have suggested. Best to you in your project!

Pat you know that most vibration in the motor is caused by misalignment of the components from the front of the crank to the 4th main. I’m not saying original pistons can’t contribute but the alignment is critical to a smoother running engine that will produce better overall performance.

Lighter pistons reduce bearing loads, and lighter pistons reduce the issues related to lack of crankshaft counterweights. Modern pistons allow for better oil control and longer ring life.

Alignment and balance are very important regardless of what type piston is used.

So a few facts, Original FORD spec produced rings were different than aftermarket rings, they were not the same OD at the top of the individual ring compared to the bottom of the ring. Unlike aftermarket rings that were the same OD top to bottom which caused the ring to wipe oil away from the cylinder and increase friction robbing performance. In period literature it even suggests that the gap on the Ford rings for each cylinder had different gaps top to bottom to insure better lubrication without increased oil consumption & loss of performance. The result, suggested that using aftermarket rings with the standard gaps caused increase wear in the cylinder, the rings and increase wear on the connecting components. Pat I would agree that aluminum pistons do reduce pressure on the engine components correctly installed but would also comment that the T engine was/is so forgiving that folklore & dare I say fact that with a little bobbed wire, leather, oil & gas you can get a model T engine running.

The original Ford rings had a tapered face to facilitate seating and improve oil control. The original bore surfaces were semi-knurled, which provided a good wearing surface with a non-glazed finish. The original Ford rings and any repro rings made to Ford spec will have a top and bottom, and they need to be installed right side up. The top ring gap may need to be a little wider than the lower ring gaps, since the top of the piston and the top ring run hottest and have the least access to lubrication. Modern type rings on modern type pistons will outperform and outlast the original style rings, and are compatible with modern bore finishes.

TXGOAT2 wrote: ↑

Thu Mar 02, 2023 10:42 am

The original bore surfaces were semi-knurled, which provided a good wearing surface with a non-glazed finish.

Please explain what you mean by the bores being "semi-knurled".

Ford, according to Ford literature, ran a device through each cylinder that forced steel balls against the cylinder walls to harden and finish the surface. I call it semi-knurled for lack of a better term.

Thanks for the confirmation!

Thank you each and everyone for all of the outstanding advice. I shall report back on completion of the mission!
Cheers, Ed

Suggested gap per period literature for new Ford spec rings were

Top .008
Center .005
Bottom .003

When putting new rings in used bores, adjust each ring gap, if necessary, AFTER placing each new ring in the bore it will run in at the lowest point it will reach in the bore when the piston is at BDC. Be sure the ring is square in the bore when measuring. The ring gap will increase by .001 or so rather quickly due to break in, so stay within the recommended specification. The foregoing is especially important when putting new rings in tapered bores. It is of little use to put new rings on worn pistons or to put new rings, or new rings and pistons, in bores that are worn beyond specified limits. Place gaps in rings 120 degrees apart.