Technical Valve o-ring

[Wouteriolio]

Hello All,
I'm having some fun this winter by rebuilding a 500cc engine that is "original" for my '71 L.

I got the car four years ago with a good 650cc block and acquired an 800cc project block that is currently in the car. Despite having these two blocks in running condition I thought it would be fun to learn how these work by buy a run down original block and gearbox and spend some quality time (plus money) on getting it up to specs again.


So far the Haynes manual, online fora and a Dutch word document on rebuilding the engine has been sufficient to figure out most details. Currently I am working on reassembling the head and I was wondering where the o-rings on the valves should go. Do I understand correctly that these are to be placed on-top of the valve guide after which one compresses the spring and refastens the top valve spring bucket with the two "splines"? It seems to me in that case that they would just be bouncing around on the valve shaft since there is no obvious retainer or am I missing something here?


Thank you for your help!

 

[the hobbler]

Some cylinder heads have valve guides that will accept proper valve-guide seals---the guides will have a length of reduced diameter where they protrude out of the cylinder head. If the guides have a constant external diameter, you use simple 'O' rings on the stem of the valve. You fit the valve in place, and then slip the 'O' ring over the stem of the valve where it protrudes out of the guide. The purpose of the seals, of whichever variety, is to prevent excessive oil running down the valve stem and thence into the combustion chamber. The 'O' ring (which should be a fairly firm fit on the valve stem) will find its 'natural' position on the valve stem after the valve has been fully depressed. With the valve, and seal, in position you then fit the springs, with the top spring collar being held in position on the valves by the 'collets. If you valve guides ARE of the type that will accept valve-guide seals that fit onto the guide, and your valves are 8mm stem diameter, I think you will find that the best seals are:---
ELRING-197-378

 

[Wouteriolio]

Thank you very much for the answer! Looking at my valve guides I see no reduced diameter and a snug tapered end so the tight 0-rings that came with the seal kit will do.