67Dart273 said

If they're not terribly loose, get a knurling kit, and put teflon valve seals on at least the intakes. These are not "normal" seals, they require a cutting tool which cuts down the height/ diameter of the OD of the guide, then the seal fits tight over the guide.

This is just an example photo, which came from this page:

http://mgaguru.com/mgtech/engine/ch202.htm

but shows you what some of these look like. Sealed Power, TRW, some others sell them



Depending on the engine, you'll need the proper cutter to trim the OD of the guide:



A typical knurling kit is essentially a "wierd tap" which you screw down through the guide, which raises material as it goes. The second part of the tool is a reamer/ burnishing tool which reams the disturbed material back to size.

Some people swear with, some swear at knurled guides. They do work, at least on engines that aren't expedted to live for 200K.

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