90+ valve guides

[tck]

On my crossbreed MK4 one of the 90+ heads had a cracked exhaust guide it is being replaced by an engineering firm it looks as it the standard guide 35537 can be modified to fit bit I note that the cracked guide has a small vertical slot in the protruding head of the guide I cannot see what that was for any ideas?

[Neville Heath]

There is an oil feed slot milled down Plus guides that feeds a radial hole to lubricate the valve stem.
Neville

[tck]

You are right the path in the head was blocked with carbon it does not seem a particularly effective idea perhaps for racing with lots of stripdowns?

[Neville Heath]

Everyone I have ever come across has been blocked with carbon. As you say O.K. for one race probably. I still clean them out though!
Neville

[Neville Heath]

Photo of Plus guide. Note seat is also tapered, not flat like Mark.
Neville