Do you do your own brain surgery also. I've heard it is expensive too.

I have had a saying that has applied my whole life to almost every endeavor. "The best thing you can know about an operation is what you don't know". What you don't know, you can figure out. If you don't know that you don't know, you are screwed. It is part of life to figure this out. You have a lot to learn.

Machinist tools won't cut valves or seats. The common measuring tools might tell you if you needed to or not, if a knowledgeable machinist were making the adaptations. I doubt that a standard machine shop would have 9mm go-no-go gauges for measuring guide wear. You might possibly have a 9mm interference reamer.

By asking the question originally you point to your lack of knowledge. Continue finding what you don't know and you will be less confident and more sure.

BTW: $4500 to repair one head, what were they doing recreating it atom by vacuum deposited atom? I don't even think 928 S4 heads cost $4500 new.

Many of the heads used in modern 4 valve applications were never meant to be repaired after major failure. I know almost nothing about Mitsu heads except that they grenade when the belts break. Working on a MB head is infinitely more doable than a Mitsu head, part of the reason the car costs 3 times as much.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician