I'm working on porting my 68 head. Porting is done, now comes the polishing. Any thoughts on how much if any polishing should be done? Should the ports be mirror finish or slightly rough?

Another question on spring seats on the head. Should I have the "high performance" springs installed with a round flat shim to support entire spring ( spring seat is not a full circle). I am concerned with the missing spring base on the head will cause premature guide wear. The late heads without the tubes have a full base . Should I be concerned?

Thanks in advance
John

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Ever stop to think, and forget to start again?

Ports, especially intake should be left rough so the fuel will not fall out of suspension. Exhaust can be polished but they are going to carbon up anyway and lose any benefit of polishing.

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Official Cookie and Mater Tormentor.

As far as the spring seats go if you are talking about the fact that there is not a machined ridge around the whole diameter of the spring seat I don't believe that is a problem. I haven't got a head to look at but as I remember there is more than enough ridge to hold the spring and shim in place without a problem. Most of the heads I have worked on are the early type and I have never even thought about the lack of a full ridge or experienced any premature guide ware.

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If you didn't drive it there, it's not a street car.

if you are asking about shims that are used between the valve spring and cylinder head, top side,
they are used to achieve a desired spring pressure and or to equalize spring pressure across the head due to variation in valve seat depths..

There is one small benefit to polishing the exhaust ports. Polishing minimizes the surface area of the port. Less surface area means less effective heat transfer from the exhaust gases into the head casting.

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