Valve guides
 

I'm rebuilding my Kohler k321 engine. My question is I pressed out my old valve guides but instead of pressing in the new ones. Can I put them on dry ice for a few hours and slip them in. Has any body tried this trick for is it just a myth?

Sounds like it would work. Years ago when R-12 was used in AC we use to squirt down such parts with that and it made life very easy.

All materials expand and contract due to changes in temperature. It is certainly not a myth...

It will also be helpful if you warm up the block at the same time. Be ready to get them in in one quick motion, or they may warm up quickly and become tight.

Not having installed Kohler guides, I do not know if there is a shoulder they are installed to or if they are just installed to a certain depth. If it is a certain depth make some way of stopping the guide at that depth before you install or ya might go too far too quick. Some sort of block you would set in the breather box should work. Try it out with an old guide that is sanded down to be too small so you can slip it in and out easily first..

According to the rebuild book from Kohler, you press it down until it is flush with the counterbore. I think that was from the top.