Valve guide replacement question

[Nebraskarider1]

When you replace the valve guides on a set of 96" TC heads is it necessary to warm the heads up to 200F or a little higher so they come out and go in easier? I did engine machine work for 15 years and still have a lot of tools so I'm doing them myself. I remember some aluminum heads we would heat the heads or the guides wanted to gall up. I see these have snap rings on them so I'm guessing they aren't running a super tight press fit. Thanks

[SP33DY]

Yes, heat is important. I use a lab oven to heat the head to 140°C (300°F) for a half hour or so to get a good heat soak. Before the head goes into the oven I swab a little bit of Press Fit Lube in the guide hole. If you don't have PFL, moly paste works good too. I like to put the new guide in dry ice before I slip it in. If dry ice isn't readily available, you can use CRC Fast Freeze Spray to chill the guide.

Drilling the old guide partway down the hole with a 7/16" drill helps to relax the press and make it easier to knock or press it out. (I have no idea whether you have a press or need to do something more medieval!) I like to use a counterbore to remove the part of the guide above the spring seat so there's that much less guide length to push through the hole.

[jsachs1]

When you replace the valve guides on a set of 96" TC heads is it necessary to warm the heads up to 200F or a little higher so they come out and go in easier? I did engine machine work for 15 years and still have a lot of tools so I'm doing them myself. I remember some aluminum heads we would heat the heads or the guides wanted to gall up. I see these have snap rings on them so I'm guessing they aren't running a super tight press fit. Thanks

On the heads that use 7 mm valve stems/guides, I press the guides out from the hot side, after heating the heads to 290 degrees for 20 minutes or so. Re-install new guides from the valve spring side. I shoot for .002" press fit. MM heads usually .0025"-.003" press fit.You cannot view this attachment..
If you go into the "Home Made Tool" section, you can see the fixture I use to press guides out.