I still see the vendors are still selling the ring sets for the cast iron original pistons. I wonder if many of you are still using them in your cars. I bought a 21 T engine at Chickasha that has STD. cast pistons in it and original valves. I am going to replace the valves in it but have been thinking of just using new rings in it. It is surprisinly good shape.
Yes I know most people use Aluminum pistons nowdays because of the weight and being easier on the babbitt.
What is the allowable bore and taper wear if original pistons are used?
And would using a set of STD Aluminum pistons work. It seems to me that they would and has anyone ever did this?
Of course the cylinders would need to be honed.
Thanks for the input.

John

I did that to my '24 when acquired. The cast iron pistons were std, so just removed them, and installed new rings for std pistons, didn't hone or bore...this was when I was 15.

Carport engine rebuild!

Had to fit one new babbitted front rod, the others just needed filing on the caps!

Worked back in '65

I am building a 21 and was working on rebuilding an engine. Last December I bought another (stuck) 21 engine. It had standard pistons. They didn't wiggle too much, all looked good. The crank was round so I just fit the rods, honed the cyls, ground the valves put on slightly used rings, recharged the magnets and got a rebuilt field coil and new bands. Runs like a champ. I may never fool with rebuilding that other engine.

I was still using the cast iron pistons with new rings up until I accidentally cracked one. They ran perfectly well. However, being a late 1925 engine, they were of the lighter construction - not much difference in weight to the aluminium ones.

For a car that gets driven all the time at high speed, the early cast iron pistons & heavier conrods would probably find the cracks in the crankshaft faster.

New valves here, STD cast iron original pistons with new rings, honded cylinders ground seats, adj. lifters, lightweight rebabbitted rods and reground crank with new babbit. About 2000 miles on it and it seems fine. I was looking more for the smoothness of the cast pistons instead of the rapid acceleration of the aluminum.

Personal opinion....it probably has more to do with how you drive your car than what the pistons are made of. If you enjoy putting along then 15 million Model Ts can't be all wrong. If you like to push the car's ablilities then if it isn't the pistons it will be the crankshaft or transmission or brakes or something else that rebels.

Better check cyls.for taper and out of round so that your new rings will seat and restore all the compression.

I vote for using the cast iron pistons if you can. I have two cars with the original engines that still have cast iron pistons and the original babbit. I have used both of them on many National tours. I also have a couple cars with rebuilt engines, with aluminum pistons. The engines with the cast iron pistons always seem to run a lot smoother. Old cast iron pistons have another use; I use them to throw at the geese to keep them out of my yard.

Can you get STD aluminium pistons?

I hate to burst everyone's bubbles, no, actually I do like to burst bubbles. But Aluminum pistons are not necessarily lighter than cast iron pistons. If you can get the really good "die-cast" aluminum pistons from about forty years ago, they would be lighter. Maybe good ones are made now, but if so, I haven't seen a new one in a long time. Every new piston that I have seen that is made for an antique is a sand-cast core. Because sand-cast is less uniform, they are cast about twice as thick throughout the skirts and head. Most of the old cast iron pistons are "die-cast" core. Plus, cast iron is stronger than common types of cast aluminum. So cast iron can be thinner to begin with, coupled with the advantage of die casting, there is so much less material in the iron piston that some aluminum pistons weigh nearly twice the iron ones.
Now to flip the coin a moment. Aluminum is a softer material and will wear the cylinders less than the iron pistons.
A side note on this subject. On another thread, I tell of the old "dirt track race car" that I restored some years ago. I "spun a donut" with that car, the only time in my life that I tried that. The car had cast iron pistons in it.
W2

I ran cast-iron pistons in the Montana 500 for the fun of it. One year I finished second running head to head with the aluminum boys. I spent a lot of time looking for the lightest cast-iron pistons that I could find. I never found ANY cast-iron T pistons factory or aftermarket that were lighter than ANY aluminum pistons. My advice is to run aluminum if you can. There is no practical advantage to cast-iron. The rings don't seal well and there can be no way that they can run smoother, as they are heavier and the reciprocating mass of straight four motors always adds a vibration proportional to that mass.

In answer to Michaels question about availability of STD aluminum pistons---I have a set that were given to me years ago--not sure if they are still available but they were once. FYI Dewey

I have a set STD alu pistons with rings at home.. Anybody wants to buy? I bought them for my T engine at a swap meet years before computer forums.. Having restored several cars and motorcykles before, I got the false impression my engine was almost unworn when I couldn't find any ridges in the cylinders.. Should have measured! The wide rings on the cast iron pistons never gives any ridges like in "all" other old engines, since they goes all the way to the top of the cylinder. Guess the guy who sold the set had made the same mistake.

Ford did produce pressed steel pistons for some time at the end of T production,Ii've read at the forum. How light were they compared to the last of cast iron pistons? I guess they were discontinued due to high production costs? Several welded together parts, I think. Or perhaps there were technical reason, since nobody else has tried sheet metal pistons as far as I know?

I know nothing about model A's - anybody know whether they had alu pistons sometimes during production, or if the pressed steel pistons were continued into Model A production?

As far as avaliability I see that the vendors sell new aluminum pistons std. thru .060.
I was thinking of using the new aluminum std. pistons without boreing the block since its not worn to much.
Anyone ever did this?

John, take off the cylinder head and do a quick measure át the top of the bores with your caliper before you order std alu pistons. It was bored to 3.750" when new, but driving on dusty roads without air cleaner changed that dimension much faster than nowadays (my latest Volvo had 300000 miles on the engine without opening it up, still ran fine)

My 1915 touring still runs the standard bore with cast piston. It runs like a top. There are two schools of thought. Aluminum pistons give you better throttle response so the engine "revs" quicker providing what appears to be more power. The cast pistons are heavier. They may rev slower but the added weight that is slinging around provides allows you to maintain a higher torque curve, thereby allowing you to climb hills a littler easier.

As to John's second question, what are considered acceptable wear limits on taper and out-of-round? I've heard no more than .004 on taper.

Dan, if you're really having a problem with geese in your yard, a piece of heavy string or cord strung about 6" off the ground a foot or so back from the water's edge will stop them. They will not cross it and eventually go someplace else.

Gary

John, I installed std. aluminum pistons in a block years ago, it ran great but when you came down a hill you had piston slap. I ran it for four years just a rattling away till I found a nos block and my father wanted bragging rights so now it is std. again.I personally think that every old engine needs bored after the iron pistons have opened up the block a few thousands.

I've noticed that old original engines with cast iron pistons run smooth. I suspect it has to do with the pistons and the fact that the cars were originally driven in the 20-30 mph range. I'd sure like to find one now. I am tired of these new engines with aluminum pistons. I'd really like to have an original good running chassis. New rings sure, new valves perhaps, but otherwise stock and original. I'd gladly give up speed for smoothness.

Gary - Your thoughts must be much like mine as you expressed an opinion ref taper but did not express an opinion ref out-of-round.

This is strictly OPINION on my part as I am certainly no expert, however I agree with Gary as far as .004 taper. However, as far as out-of-round, I am not sure what the acceptable limits would be. I seem to remember that Hastings would guarantee their rings up to, but not exceeding .004 taper, but I don't know about out-of-round.

Again, OPINION on my part, but I think that it's possible to get away with up to .004 taper, and, altho' I wouldn't recommend it, perhaps even a bit more. The thing to keep in mind is that the rings will flex with each up and down stroke to comform to the tapered cylinder, and this is why you can get away with a bit of taper. How much and for how long the rings will stand the constant flexing with each stroke before they break is the question. I would think that it would depend on the type of ring, i.e. cast iron, etc.

Concerning out-of-round, I've seen rings with a series of very fine grooves in the edge; the designers thoughts being that these grooves provide a series of high spots (similar to very, very fine screw threads) that will wear quickly to aid in the quick sealing of the rings during the break-in period. You have to look really hard to see these grooves and I wouldn't think that they could be much more than a thousandth or two deep, and in my estimation, any out-of-round of the cylinder should not exceed the depth of these (for lack of a better term) "break-in" grooves.

Again, a lot of words to say that new rings will conform (by flexing) much easier to a few thousandths taper, but brand new round rings will take forever (if ever?) to "wear in" to any out-of-round that exceeds the thousandth or two depth of the "break-in" grooves in the new rings. The problem being then that any out-of-round that the rings do not conform to will allow compression to leak by one way, and oil to leak by the other way.

Again, more words to say that you can get away with a few thousandths taper, but more than a couple thousandths out-of-round will result in less than max. compression and some oil consumption.

So, my advice is that whenever possible, bore the cylinders and finish with proper honing when you install new rings. FOR BEST RESULTS, ALWAYS INSTALL NEW RINGS IN A "PERFECT" CYLINDER! (And be sure to provide sufficient ring gap) keeping in mind that if the ring gap cannot be perfect, a bit more is much better than not enough!)

Sorry for the long, "wordy" post, but John Kuehn did ask about the "allowable" cylinder wear.

The flexing of the rings due to taper will also cause the grooves in the pistons to wear out much faster. So although the outer diamater will still seal around the cylinder wall, the oil will be drawn by vacuum around the grooves into the cylinder. That is the reason they used to send the pistons out to be re-groved. The grooves were re-cut and then thin shims were placed between the grooves and the rings, or wider rings were used.
Norm

Thanks Harold. Not an expert in this area but logic says an out of round condition would be more critical than the taper. Although neither is a good thing. Wanted to get an idea what is considered by experianced T'ers to be allowable wear. Checking my engine I've found taper and out of round up to .007. Not good. Plus I have some scores from the piston pins. I've found working with a T to be anything but "boreing".

Gary