7/16 is not 11MM Grrr
Original valve stems were 7/16" Indian valves are 11MM. Some of the guides are correctly sized for 7/16 valves, some for 11MM . I have seen brand new heads with 7/16 guides and 11MM valves. Leaving almost .004 of extra clearance. Check this out and correct if needed. 7/16 guides can be knurled and reamed for 11MM valves.
Okay, so the above described valve to guide mismatch applies to my engine. Being the over-thinker that I am, and the fact that I am a sucker for making a project more complicated than it needs to be at every opportunity, I was thinking about sleeving the guides. My thought was to bore the existing guides to 5/8 ID, then press in and bore and brush some bronze sleeves. My thought process behind this is to minimize blow-by, which could offer some small (perhaps very small) increase in efficiency, decrease oil consumption/smoke output, and potentially increase lifespan/TBO. The plan is to go towards the lower end of the range on clearance (.0015-.0025) given bronze's higher COE and greater resistance to galling. It seems from my reading that a closer fit is normally permissible when bronze guides are used.
Info is scarce on the specific alloy that might be the best fit, but from what I
can find, and some reading on the alloys themselves, I am leaning towards 544 (phosphorus-bronze) which seems more common in the application, or 954 (aluminum-bronze) which seems like it might be a bit tougher/longer wearing.
Another option I suppose is to replace the guides entirely by machining new bronze versions as well...
Do any of the experts have any input for me on this?