My01 xc70 awd B5244t3

The cyliderhead needs refacing = I am going to get it checked at an egineering workshop tomorrow. It did not suffer overheating and the valves are in good condition. I am worried about how much metal can be machined away as the tollerances specified in Vida are very tight: lengthwise max 0.5mm 0.001968" and crosswise max0,2mm 0.007874". If the shop want to machine more than that is there anything can be done to mitigate? I have read that heads can be bolted to a thick steel plate and held at 500 degrees for several hours before being cooled down naturally which sometimes lessens warpage. If a donor head and its partner head cover are used does it have to be machined to fit the camshafts or what? All information welcomed.

Quote:

---

Originally Posted by nickbw

I have read that heads can be bolted to a thick steel plate and held at 500 degrees for several hours before being cooled down naturally which sometimes lessens warpage.

---

What you describe is what I know as "straightening" the head. Every head I send to the machine shop that is remotely warped has that done to it. The problem with a warped overhead cam head - is the top is warped also. So the cams are trying to spin in holes that are not aligned with each other. I think that's not a good thing and straightening might fix that. The machine shop explained that a complete valve job is needed after heating the head up "because things move around"! Made sense to me because I would certainly squirm if bolted to a flat plate and heated to 500 degrees or so for a few hours.