I could allocate some time recently to work on the heads. If you follow this post from the beginning you may remember that timing got messed up in this car and pistons contacted the valves in bank 123. However, the valves looked perfect, no visible damage whatsoever. So the heads were rebuilt and ready to go. Yet, it`s been a long time since I lapped the valves and reassembled the heads, just enough time to get paranoid about it. What if the valves somehow got damaged due to the impact from hitting the piston head even if it`s not visible and will get stuck in its bore and seize? Very unlikely, but I wanted to sleep well, so I ordered new valves from Pelican, lapped them and reassembled the head. Again.
I checked the seating with this classic method when you pour gas on the valves and see how long it takes for it to leak down. After an hour it was still in the chambers, so it should be ok.
Then I inspected the heads for deterioration/possible warpage. I placed a straight edge on the cleaned surface and tried which is the thickest feeler gauge that I can slide in between the straight edge and the head. The thickest was 0.03mm. In the shop manual this is exactly the highest tolerated value for a freshly resurfaced head. The tolerance for a used head that you still can put back on is 0.05mm. So that`s great, no need to take the heads to the machine shop.
I inspected the head bolts. These are stretch bolts, so you must replace them if they are stretched over their limit, i.e. they won`t be able to produce the same clamping force any more. There is no specification about this in the shop manual, but it is also not stated if these bolts should not be reused. So I ordered one brand new bolt and compared its thickness and length to the used ones. There was no significant difference between them, so I concluded they should have one more round. Yes, I`m cheap, I know.
I had good results with this brand so I went with this.
Looks like a few bubbles got trapped during the casting procedure. Another day when the quality control guy was on vacation. Luckily it`s not a critical spot on the head.
Now it starts looking like a flat engine, or as they call it where I came from, a boxer.
