Piston Expanders?

[john in illinois]

We tore down a Model A engine a couple of months ago that had those in the pistons. Had no idea what the were for.

John

[rotorwrench]

They would only work on a split skirt type piston. Not sure if they were intended for steel pistons or aluminum or both. I don't particularly like the idea of expanding an aluminum piston that way. Some piston skirts fail without any help like that. It doesn't make much sense to help them fail in my way of thinking.

[DD931]

Back in the day, piston expanders were common. Various approaches. I remember ones that were made of spring steel and worked on the piston pin bosses to encourage that part of the piston to expand. Had to be installed with special pliers to get them properly in position. Seems to me I used them on the flathead six in the family '48 Dodge. Might have bought them from Montgomery Ward.

[joel rapose]

When I learned engine repair lots of years ago...we were taught how to knurl piston skirts...then we would undercut the ring grooves and install what was called "expanders" it really worked well...the knurling not only made the skirts expand but held oil in the skirt area... It was cheep and common in the 40' and 50's

[40 Deluxe]

Things have reversed over the years. I have a 1947 Motor Manual that also has a labor and parts section. For example , a lot of new pistons were listed for around $10 each, while labor rates were around $2.50-$3 an hour. So it was cost effective to "rebuild" a piston by knurling/resizing/expanding, cutting the top ring groove and installing a spacer, and honing the wrist pin bore (and rod) for an oversize pin. If the cylinder bore had a lot of taper, you just cut the ridge with a ridge reamer and maybe put expander springs behind the rings. I remember overhauling a few engines with as much as .019" taper and they ran pretty good with no smoke or oil burning so I set .019" as my limit on wear before needing a rebore.
Today, you can still find a new piston for a 350 Chev or 302 Ford for around $10 (imported, true) while labor is $80-$100/hr.
And don't forget the tapered shims for worn bearings and/or crankshafts! These were sheets of brass shim stock that was, for example, .002" in the center and .001" on the edges. So you cut a strip the width of your bearing insert and put it under the lower insert. By being .002" in the middle and .001" on the sides, it took up .002" wear evenly. It came in different thicknesses.

[Marv]

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I have some of the piston expanders that are new. They were used in the steel pistons to eliminate piston slap. That is what I was told by an old time mechanic. He did not mention using them in aluminum pistons.

[grumppyoldman]

I kinda hesitate to tell this, but my Dad told me back during the Great Depression he used bacon rind for rod bearings. I got a big laugh out of it and asked him how that worked. He told me the old Model T' didn't run fast, and they didn't drive them very far because they couldn't afford gas. When they started knocking they just replaced the hog rind bearings. I still smile to myself and think how hard it had to be in those days, I still have a pic when I was 2yrs. old wearing a gown, because that's all he could afford and mother made that. Al

[supereal]

That's new one one me, too. When I was a Ford mechanic sixty years ago, we regularly had pistons knurled on an in-house overhaul if the owner wouldn't spring for an "authorized" Ford rebuilt engine. I suspect the "expanders" would adversely affect piston weight.

[FrankWest]

Originally Posted by grumppyoldman

I kinda hesitate to tell this, but my Dad told me back during the Great Depression he used bacon rind for rod bearings. I got a big laugh out of it and asked him how that worked. He told me the old Model T' didn't run fast, and they didn't drive them very far because they couldn't afford gas. When they started knocking they just replaced the hog rind bearings. I still smile to myself and think how hard it had to be in those days, I still have a pic when I was 2yrs. old wearing a gown, because that's all he could afford and mother made that. Al

Funny stuff.....I wonder If we can extend the life of Babbitt bearings using Bacon?

[tubman]

I have hear tails that some guys who experienced rod bearing problems on model T's, while on the road, would cut sections from their leather belts to make a temporary repair.

[richard crow]

piston expenders were installed in the piston. the theory was when the eng got hot the steel expender would expand thus increase the piston dia .years ago we did a lot of in frame eng rebuilding it was cheaper. did it last where i was most cars were driven in the city at slow speeds & yes they held up well. we did not use crome rings as they were hard to seat. money was tight. no credit cards. most house holds had onley bread winner.no body had 90 dollar shoes or 500.00 cell phones

[B-O-B]

As Bored&Stroked has posted we as a nation were not always a throw away society. During WWll & the depression you made do. Folks today do understand that. Just get on the smart phone & order a replacement made off shore.

[56markII]

Years ago I used knurled Pistons to tighten up slightly loose Pistons and they lasted a long time. One trick was knurl them heavy on the coast side of the piston and not on the thrust side to make em last longer. Machining the ring grooves was also common because if the piston has very little wear on the skirt truing up the ring groove and installing spacer rings was also acceptable. What happens if the engine you are working on has very expensive and or very hard to find Pistons ???
If it works do it. An out of round or tapered cylinder is worse than a fairly straight cylinder with slightly loose Pistons. The rings don't last long if taper is bad and don't seat very well if out of round.