[Peter Zimmermann]

Originally Posted by john_cramer

The metallurgy of the head will be permanently altered, it's a paper weight.

OK, 956 or 962 heads had a "squish area" but I'm not sure that was welded, it may have been machined from a blank casting from Mahle. Plus race heads probably got changed after every (professional) race.

SC: Based on personal experience I don't agree with the above. Over many years, 25 +, we repaired so many heads that others had "repaired", and blown out ports at the guide because they didn't; (1) heat the head to achieve the correct press, or (2) machine the O.D. of the new guide to the correct dimension. We did heads in-house for many years, and since I closed the machine shop have had a number of them done by my referral, and have not had a single failure. EMS has even restored damaged combustion chambers for us, which involved removing both seats, welding and machining the chamber, and installing two new seats. Same story - no failures. I'm sure, like everything else, the quality of the welding is paramount regarding these repairs, and I'm quite sure that if the welds are not done by an expert the result might be very different.