We now offer head restoration services in addition to our regular valve job services on 928 heads.
Many owners find that, when they remove the heads off their 928 (for a valve job or head gasket replacement, usually) that the corrosion of the heads is so bad they see no way the gaskets will ever seal again.
We have a process where we bead-blast all the corrosion out of the heads and weld them up to replace the missing metal. Then they are milled flat while we look for more porosity. If found, we weld them up and mill them down again, and keep doing it until we get a good gasket surface.
The pictures below are of GTS heads and we had to cycle through the weld-up/mill down process three times before we were happy. Given what replacement GS heads were costing, this customer was delighted to save his car for so little.
We do this for $310 for each 16v head and $360 for a 32v head. A valve job usually done at the same time and is not included in the above price.
Pics below show his GTS heads as we received them, after bead-blasting, after the weld-up, and then final as shipped back to the customer.