pressing pistons to rods

[Bain]

I'm guessing no but before I learn the hard way I'm gonna ask. When pressing the pistons on to their rods is that any need to lubricate first? I would think no because it would stick better that way but once again I would hate to get them on and find out otherwise. Thanks

[MagicRat]

Warm the pistons in your wife's or g/f's oven to about 150 deg. or so. (Tell her its a new and exotic style of cookware.) Throw the piston pins in the freezer for a while.
The thermal difference between the two will really help installation.

[curtis73]

Agreed. When a shop does it, they heat the small end of the rod pretty hot. I don't know how hot, but the pin slips right in like a zero fit.

Don't physically use a press to put them in, you'll damage the whole works

[Bain]

Your kidding so I heat it up to 150 then put it in the freezer till its cool enough to touch and just slide it in? That's unreal I'm glad I asked first because that is something I would never have thought of.

[curtis73]

Yeap. Press-in pins refers more to the clearances involved more than the method used to install them. If you install them with a shop press you'll most likely cause stress fractures in the rod and failure will happen soon after. The secret is not to stretch the rod metal by pressing it in, but to let the metal relax around the pin and heat is what most commonly does the trick.

So, you heat the rod to 150 and put the pins in the freezer. The pins contract and the rods expand. Assemble them and let them get to room temperature and they'll be press-fit without the pressing.

[Bain]

Ok what do you do when you've heated up the rods and frozen the pins and you still can't get them put together? I heated them to 150 but that didn't work so I kicked it up to 200 and that still didn't work. Any other ideas or tricks?

[Evil Result]

you could take a blow torch to heat up the end but not too hot i'm shure something around 400 degrees would work you just want to avoid messing up the grain structure in the metal making it more prone to fatigue.

[curtis73]

This one is out of my league since I'm not a metallurgist, but I'd bet a machine shop would let you know a good temp. There are different ways to tell by the color of the metal. Like, "cherry red" indicates a certain temp range and "white-orange" is where it turns into a puddle of goo.

I know when I get my rods back (I usually let the machine shop do that) the small ends are all discolored from the application of heat.

[Bain]

I'll try a blow torch. I can't stand to let anyone else do something on my cars that there might be even a small chance that I could do it my self. So I really don't want to have to do that here.

[Austin8214]

wait on the blow torch. I would use a pot of heated motor oil to heat the rods up. I do it alot a work with press fit roller bearings, and they slide right on. Do not get the oil over 450 or 500 degrees though or it will remove some qualities of the metal if you get them to hot. This is also nice because the oil provides some lube.

[Bain]

Cool, alright I'll try that first them thanks

[SaabJohan]

My tip is to used liquid nitrogen to cool the "inner parts". Unlike heating cooling won't damage the parts, unless you drop them or something like that.

[public]

Turn your freezer thermostat down. Liquid nitrogen is just a little hard to find. And they usually won't sell you a thermos full.

[SaabJohan]

Usually you can rent a thermos, and buy the liquid nitrogen.

Dry ice can also be used, but one can't reach as low temperatures with that.

http://www.linde-gas.com/Internation..._shrinkfitting

[Bain]

Originally Posted by SaabJohan

Usually you can rent a thermos, and buy the liquid nitrogen.

Dry ice can also be used, but one can't reach as low temperatures with that.

http://www.linde-gas.com/Internation..._shrinkfitting

Thanks for the link it sounds like shrinking the pins are more important than expanding the rods. Thats good cause I tried heating it up in oil today and I just couldn't get it hot enough so it didn't work either. I'll try dry ice on the pins and maybe throw the rods back into the oven at 200 or 300 tomorrow then and let everyone know how that turns out.