Rebuilding 1927 block but have to use castiron pistons when I opened it up two were cracked have box of pistons but I was wondering how to do figure out what is a 26-27 piston and the earlier model piston I guess there is a difference but I don't know what it is, is there a mark or something? Second question need to rebore to straighten the bore am I better off to resleeve to standard or to try and find oversize pistons to keep cast to cast surface for same heat expansion since sleeves are differnt metal.

I would suggest oversized aluminum pistons. Jim Patrick

I second that motion! Oversize and use aluminum.

The 26-27 pistons are the same as the later years version. You can tell them apart by looking at the inside. Just compare to those you are replacing.
Cast iron pistons came in .0025, .005. .032 and .038 OS from Ford. Others made cast iron pistons in increments of .010 OS
If your bore is out of round or tapered, I suggest rebore and go with alum pistons since the cast iron are no longer available. Even if you need to sleeve the cylinders because of damage, I would go with aluminum.
However if you can find a balanced set of cast iron, the later style, that will fit your rebored cylinders, I'd seriously consider using those. Rings for cast iron pistons are still available.

I run cast iron, but if I had to replace them, it would be aluminum.

Rick, the 26-7 castiron pistons have a ridge (ring) on the inside of the bottom of the skirt. The heavier, earlier pistons have straight skirts on the inside. What is most important is not the style, but rather that they weigh close to the same.

I will put in with everyone else and recommend aluminum in any case.

I thought I read somewhere that the last year of T production 1927, that Ford started to use aluminum pistons, or was that just another myth?

Sounds like you got some bad information Kerry.

Thanks for the response it helps alot wish I could use aluminum pistons but the club rules are cast only. Saves a lot time looking thru swap meets, garages,, boxes, knowing automatically which pistons are going to be lighter.

Kerry, I think you were thinking about the light weight tin pistons Ford started using in 1927 - perhaps on replacement engines after Model T production was stopped?
In 2008 Jim Sims posted this picture of the two versions of tin pistons he has:

They were welded together, the left one from 7 parts, the right one from 5 parts. No wonder Ford left the concept.
http://www.mtfca.com/discus/messages/50893/74837.html?1228752482
Did Model T replacement engines made later in the 30's up until '41 have cast iron pistons again like this one with late X rods?

Picture by Bill Harper in this thread 2006: http://www.mtfca.com/discus/messages/29/12003.html

I've never heard of a club that has a cast only rule. Seems like it would drastically reduce the number of qualified members, as I know of very few that choose to keep the cast iron pistons when doing an engine overhaul, as Aluminum pistons are the accepted alternative and are superior to cast iron due to their light weight, noise reduction and increase in engine life they provide.

On the bright side, at least it wouldn't cost much to provide snacks to the two members (you and the president) at your cast only club meetings. Jim Patrick

Someone posted here a long time ago that there really wasn't much difference in the weight of the cast iron and aluminum pistons. Has anyone ever weighed them?
Somehow, I suspect Tom Carnegie has!!!

It's my understanding that Ford quit using Cast Iron pistons after the Model T. I don't recall ever seeing a Cast Iron piston in a Model A. There is quite a difference in piston weight with the Aluminum at 1 lb 3 oz and the cast iron ones at 2 lbs 1 oz. The ones I weighed had no rings or wrist pins. The Cast one was standard and the Aluminum was 20 over.

Fred S. is right. I have weighed a bunch of them. I have have found cast ones as light as about 1 LB 13 oz. I ran in the Montana 500 a few times with cast iron pistons and did quite well. I think I finished second once with them. The trick is to get the rings to seal up, which is very hard to do. There is no up-side to running cast in my opinion though.

I think Fred from Skwim is correct, model A's never had cast iron pistons. I do have a set of aluminum pistons for a T on a set of X beam rods. They look like they are of the era, but may or may not be original Ford pistons.

Rick runs his car in Tillamook, Oregon's Pig 'n' Ford Races. They have their specific regulations, just like the Montana 500 people do.

: ^ )

Pig 'n' Ford? Is that the one where you drive around holding onto a live pig? Seems I remember a post about that, about six or eight months ago?