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I confess, while my heads were off, no valves in, I did get the Dremel out and smoothed out the casting a bit, especially around the 'mound' where the inlet valve enters the casting. I was a bit frustrated, waiting for my pistons and cylinders to be returned to me..... Several hours work (all @ £0/hour) for about 1/2 of a bhp I expect.

 My 2p as ever.....

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I think we should change the name of this thread to who likes "Pork Scratching" ...................

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Really late to this.  Anyway...

The main (or obvious) issue is usually the step from the port to the exhaust manifold as the manifolds are invariably smaller diameter than the head - especially with SSIs.  Accordingly, the biggest gain is in removing that step.  And its easy, because you are working on the (relatively) cheap exhaust, not the head and you can do it with a dremel and grinding bits.  You can also remove the exhaust and do it on a bench.  Meaning its DIY - I did it on my old exhaust.  On the other end, the intake pipe diameter should match the intake ports.  Going 964 intake on mine, I needed to have an adapter, which also took care of the step in size IIRC.  I recall some dremel action on that as well.  I never touched the heads.

Real porting and polishing of heads is as much art as science and costs what it costs.   Once you smooth the obvious bits (noted above), the gains are minimal.  Porsche heads flow well compared to the vast majority, so the benefits are much less on air-cooled f6s than other examples.

 

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