New block

[bystander]

Thanks all for quick replies.
There definitely aren't any liners and the bores look good with no scoring or marks.

Core plugs are screw in, with large 'screw head' across them. Should I unscrew these, as I of course don't know if they are leak tight, and if so should I reseal threads with blue hylomar or is there a special sealant/gasket?

And to clarify, I will need the flanged valve guides, but then I fit collet style valves?

thanks again
Andy

If the core plugs look ok I would leave them alone, they are unlikely to leak if they haven't been disturbed, and would probably be a real b*gger to undo (although saying that, it might be worth taking them out to clean out any accumulated crud in the block). No problem with valves, all types are the same stem dia. (apart from the Reliant replacements that were around a few years ago) and are all interchangeable using the appropriate fixings.