My ECZ-G's have thin wall brass inserts, installed before i got the car. The cup type valve stem seals were siliconed to the guides. I did not think this a good idea (no lubrication to the guides) so i pried them off and have installed new floating cup type. Will not be able to run the engine 'til next year.

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South Australia

Boring, drilling, or reaming are the typical operations for installing many of the replacement guides or liners.
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First and foremost is always check the valve stems for wear as subtle amounts of wear here adds up in a hurry. Beyond that, there are several ways to fix worn guides. Knurling is the car lot repair and not recommended as a long term fix. Drilling or boring out the original guide and installing an iron or brass replacement is another but this one can become elaborate and expensive. Bronze guide liners is the least expensive and easiest but make sure there is adequate clearance on the stem and liner to reduce the odds that the liner is not seized upon and pulled out of place. Screw in bronze guide liners are my choice for most iron heads.
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Here’s the link to a past thread talking about guide repair.
http://forums.y-blocksforever.com/Topic7050.aspx

Lorena, Texas (South of Waco)

Thanks Frank. I've never seen guide liners & wasn't aware they were steel, I presumed that they were a bronze alloy of some sort. Do they normally require boreing for clearance to install ?

Paul

Paul,
You'll get more answers to this. The Bronze guides will last longer but require a bit more Valve stem clearance. They are typically more expensive to purchase and install that steel liners.

Frank/Rebop

Bristol, In ( by Elkhart) 

Can someone clarify for me, the differences between having bronze valve guides installed in a cast head vs installing guide liners? When is it appropriate to use the guide liners & when isn't it? Are both readily available, and is there a significant cost difference? Thanks

Paul