Just a quick question. Took my head apart for machining work and now can't remember if the two part valve caps go on the inlet or exhaust valves. Haynes doesn't say and the diagram is unclear in my copy.
Would be grateful if someone could confirm please.

Cheers, Steve.

2 part caps on exhaust valves

Nick

Anyone know why they had them?  

I remember a tuning book saying "fit the single piece inlet caps to the exhaust valves".

Thanks Nick, much appreciated.

Steve.

The two part caps spin the valve— can't remember the reasoning why— to keep it cool somehow?

James,
I think spinning the valve is meant to keep the valve seat, and the seating surface on the valve itself, cleaner. That way the valve stays gas tight longer and is less prone to burn in the case of an exhaust valve. The bad side of rotating the valves is that the arrangement that spins the valve is heavier than a plain valve retainer and thus requires more spring pressure to return the valve to its seat and keep it there. Or viewed differently, valve bounce will start at a lower RPM with the rotaters than without.
                                                                                    Cheers,
                                                                                    Paul

The factory parts catalogs for the GT6's list the inner/outer valve collar types as for "exhaust only".  The intakes have the single piece valve collars.

All the cotters which hold the pieces together are of course 2-piece split cotters.

A factory parts catalog is essential for reassembling your car:  you not only see how the pieces go together, you see what the previous mechanics lost or screwed up!

Quoted from James

The two part caps spin the valve— can't remember the reasoning why— to keep it cool somehow?

Evens wear, and helps prevent localised hot spots (though the second point is less likely to be an issue on such small valves). Bigger engines actually have turbine blades fitted to force the valve to spin.