How much is not enough?????

[AussieJohn]

What valve guide clearance is needed when running valve guide seals? Is it advisable or not to run it at the tight end of guide to stem specs? Any thoughts or experience, cheers, John.

[nigelrbfurness]

As far as I know, valve stem seals (if that's what you mean by guide seals) are not used in twin-cam cylinder heads, I was told years ago that this was to provide a degree of upper cylinder lubrication but I have no idea if that's true. Someone else told me it was to make sure the smoke was always blue :~ It might be worth looking at the specs for engines with similar valve and guide material that do use seals to see what is recommended for them.

Nigel F.

[types26/36]

The standard TC engine does not have valve seals and I read somewhere (maybe in the Wilkins book) that the dimensions just dont allow the space for them.....but that said there IS a modification to allow them to be fitted.
I did try to fit some a long time ago using Toyota or Mazda seals but it was not very successful but that's another story...

[AussieJohn]

A friend is building an engine with modified guides to take the seals, the question of clearance came up so this is why I posted the question; I hoped someone may have had experience with this mod, maybe Rohan can shed some light on the problem, thanks for your inputs, cheers, John.

[rgh0]

The specification valve stem clearances are also required to ensure the valve seats properly and does not move around on the seat and not seal well. With stem seals I would not be quite so paranoid about aiming for the bottom of the specification range for the inlet valve stems as I do without stem seals to minimise oil burning . I would aim for the middle of the specification for both inlet and exhaust valves

cheers
Rohan