MTFCA Forum

A friend of mine is new to model Ts and is sending me pictures as he’s doing some initial engine inspection. He says one of the cylinder walls has these two marks. Do they look familiar? The pistons are marked with script “Ford .031“

The scoring in the cylinder was caused by a loose piston pin.

I’ve never had loose pin. So I assume its a typical pattern for pin scoring. What are his options at this point? Boring or a sleeve?

I would probably Sleeve it. Reuse the pistons and keep all 4 the same size

Ok .. so that’s engine removal time. Anyone know a model T friendly machine shop in central pa?

Sometimes, it is simply a mark. Is the engine down for rebuilding? Then fix it. Is the engine down because it knocked? Hone it (and the other 3) and put in new rings (if the bores are within reason). Do not automatically assume this will burn oil (unless it did before teardown). When I did Tim Moore's new rod during his trip, there was one cylinder (#3 I think) that had a doozy of a mark from long ago. That car did not smoke when the #2 rod was replaced and was put back together (and boy, did he drive that thing hard). You might be surprised what a T engine will tolerate. That is one actual example...I have seen others as well...

More than likely not a loose pin, 2 other problems cause the pin to score the bore, first the babbitt is worn out on the sides of the big end and second the pin bush is not fitted correctly in the piston to stop the rod from floating across to the bore.

A very good friend of mine many years ago had a nearly NOS replacement block that had obviously been run some amount many years before. It had one cylinder with a score like that, and deeper than I would like to see. (Pure speculation, someone had bought a replacement block and didn't know enough as a mechanic to put it together correctly.) He was in a rush to make an upcoming meet, so after a short discussion, he threw it together and ran it hard. I don't think that thing smoked at all, and performance sure wasn't hurt by it.
One other thing you need to check for! A bent rod also can cause the wrist pin to run hard on one side and cause a score like that. Bent rods usually knock, but not always.

Best fix is always to do it right! But sometimes, time or finances make that difficult. From what I have seen myself, such a score by itself doesn't seriously hurt a motor.

As others have indicated, model T will run quite OK with such a score in the bore. We have a club member who blew a head gasket on a national tour in 2004. He had owned the car some years by that time, so it had been there a while. It's still there, the car is still going strong, and the repair will be done when he as the transmission overhauled.

Allan from down under.

https://www.facebook.com/ucfmachineshop ... =1&theater

Mark........I have used UCF machine shop in Carlisle, PA with excellent results. The shop foreman is Mike McCommon........Regards, John Jackson