I’m not 100% sure, but I suspect the white deposits on the exhaust valves of cylinder #1 is due to oil burning and/or running lean, and it’s interesting because it’s only that cylinder. So it doesn’t seem to be a valve guide seal issue (i think). My S40 (non-turbo) had the same residue on #1, #2 and #5. I think it’s unlikely to be burning coolant symptom, because mine was leaking on cylinders #2 and #3, and #3 was ok.
One thing I believe it could explain why, is due to the proximity to PCV nipple at the lower intake manifold, that connects to the turbo check valve via the aluminum pipe that runs behind the camshaft sprockets. That check valve is what let the PCV vent gasses when the intake manifold is under boost. I think when gasses are routed through there, small amounts of oil builds up and when the throttle body shuts, creates vacuum instantly at the manifold, and cylinder #1 eats up all that oil. This is just a theory, but I’d like to know what you guys think that could explain this.
Going back to topic, you already have the cylinder head out, I don’t see why not pull it all apart, replace valve guide seals (get the special plier for this to make it easier the removal), inspect the condition of the valve sealing surfaces and determine if it needs a valve job or not (hopefully not).
The other big question is if the cylinder head is warped or not. You can confirm this with a straight edge, or simply by placing the cams on the head journals (remove the cam sprockets before doing this). If there is up/down rocking movement at the cam ends, the head is warped.
If the cams sit flat on the journals and won’t rock up and down, great news!. Just carefully clean it up using simple green pro HD (purple color) mixed 1:3 with water and also do the same with PCV (I posted photos of the before/after cylinder head here).
If it’s warped, you have two options:
- Bring it to machine shop that will straighten the head before resurface it, otherwise, the cam journals will stay distorted. This is not a pushrod engine.
OR
- Reinstall the cylinder head just like that. It will straighten itself when torqued to the block. This is not ideal, but it worked on my S40. In my case, cylinder #3 was the highest part, so i did the 20 Nm and 60 Nm stages per VIDA, but then loosened all bolts except the 4 bolts surrounding cylinder 3, and torqued them up to 60 Nm following the torque stages and sequence. Once all bolts were at 60, checked the ones surrounding cyl 3 (they were a bit loose) and brought them up to 60Nm again. Then I finished doing the angle sequence. With the head on the bench, the cams rocked up/down, but once it was torqued to the block, the cams sat flat without any play at all.
Regarding valve clearance, you can check it with the cylinder head on the bench, but the final and most accurate measurement will be with the cylinder head fully torqued to the block.