Valve guides
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The "top" of the guide should protude 13.2 mm(shims removed!) i.e. camshaft side NOT where the guide protrudes into combustion chamber.
Porsche recommends "coring" out the old guide from the camshaft side with an 11mm drill to weaken it and allow it to press out easily.
I would NOT recommend that method.!!! If you can make or have made a suitable drift/mandrel that is stepped in such a way that the inside of the guide is filled with the drift all along it's length (to stop the guide collapsing) and the outside of the drift is virtually the diameter of the guide . Use the drift to remove the guide whole without coring(use a suitable press). You will find that with care the guides will remove easily and you will also be able to fit standard size guides NOT oversize ones. I also put my heads in an oven and heated them carefully to help the process of removal.
The drift wants to be approx 150mm long the first 90mm should be 12.9mm in dia the remaining should be 8.9mm in dia all sizes approx take a good look at the guides first. You may also wish to make a tool again of round steel bar that allows you to set the depth when installing the guides. a 15mm+ round bar with a 13mm appx(guide o.d.) counter bore 13.2 mm deep will make an ideal setting tool to place each guide at the correct height.
Minor disclaimer........it was eight years or so ago that I did this so my memory may be a little weak on the detail. Data good for 74 and on. So check exsisting guides to confirm validty.
Porsche recommends "coring" out the old guide from the camshaft side with an 11mm drill to weaken it and allow it to press out easily.
I would NOT recommend that method.!!! If you can make or have made a suitable drift/mandrel that is stepped in such a way that the inside of the guide is filled with the drift all along it's length (to stop the guide collapsing) and the outside of the drift is virtually the diameter of the guide . Use the drift to remove the guide whole without coring(use a suitable press). You will find that with care the guides will remove easily and you will also be able to fit standard size guides NOT oversize ones. I also put my heads in an oven and heated them carefully to help the process of removal.
The drift wants to be approx 150mm long the first 90mm should be 12.9mm in dia the remaining should be 8.9mm in dia all sizes approx take a good look at the guides first. You may also wish to make a tool again of round steel bar that allows you to set the depth when installing the guides. a 15mm+ round bar with a 13mm appx(guide o.d.) counter bore 13.2 mm deep will make an ideal setting tool to place each guide at the correct height.
Minor disclaimer........it was eight years or so ago that I did this so my memory may be a little weak on the detail. Data good for 74 and on. So check exsisting guides to confirm validty.
Sounds like you need a copy of the Technical Specifications booklet for your model - better to be safe than sorry. Available from Porsche Centres for about £15 - can't remember your car's part number for this but mine is WKD 422 420 - if they find this they will find the others (in a series of about 18 booklets)
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