I decided that maybe it would be wise to take apart my new piston/rod assemblies, and weigh out the parts to balance.
I set an assembly on a press and began applying pressure, taking great care to use wood blocks up as close to the pin as possible. The pressure was enough that the wood made creaking noises and was dented, and so I decided not to risk cracking the aluminum piston. The wood creaked only twice ( 2 pumps of the press handle, and then I got cold feet and stopped) I may only have moved the pin a millimeter, and the rod is still well centered on the pin, when the pin is flush inside the piston at both ends. However, now there is a noticeable increase in resistance when I try to rotate the rod. It does not feel like an uneven resistance. When the pistons were initially put on the rods by a shop, there was a very slight difference in the stiffness of the pins' rotation between a couple pistons, but this resistance is more than that. We are not talking about needing to force the pin to move freely, but the rod certainly will not flop around on the pin as it did before.
Anyone been in this situation before? Adivice?

Is there a special type of press needed if I wish to keep the pistons for reassembly?
Thanks

there is a special type of press for this, it uses special piloted arbors to keep everything straight and lessen the chance of bending a pin or cracking a piston. You would die if u saw the amount of force required to remove a piston pin

Kevin

See this ebag auction for an example of the tooling.
The needed parts:
- A piston support or "nest" that keeps the piston square to the press ram and spreds the load over a wide area.
- A pin driver that pilots off the i.d. of the pin , has a square shoulder and clears the pin bore in the piston.
- "U" shaped steel inserts, that go in-between the con rod's small end 'eye' and the inner piston bore surface, these keep the narrow edge of the rod from 'swedging down' the pin bore, as the pressure is applied.

In general, it is hard to get pressed pistons off the rods, without distortion or breakage, even with the correct tools.
DD

OK, maybe I'll live with the pistons as is. This car will not be on the track.

So, based on the description I gave, is the piston ruined? I did slide the pin left to right a few times, and the con. rod seems a bit freer if slid to one side than if centered, as it would be in the motor.

ANd thanks for the info.

Is this a new piston you can get a single of without too much trouble?

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ski

Take it to a shop and have it installed. Ask for the price over the phone. It shouldn't be much.

2¢

CJ

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Part of Tyrde-Browne Racing

Measure the piston's OD to see if it is still OK.
If it measures OK, oil and "work" the pin to loosen it up... then run it.
DD