Need help about head & piston condition
 

As mentioned in my introduction post, I'm rebuilding a D24T to fit a 740 GLE Polar.

The car came with a spare D24T in it. This one's really smokey.
The original motor came out of the car, got 140 000Km.
Ex owner said compression was bad, this is the only background I've got about that engine.

So, I finally took it into the shop and opened it up all the way. There was only 2 gaskets present : head gasket + exhaust gasket. All other gaskets were missing.


Anyway, let's jump into troubles. Got confused about both the head and one piston.

First, the head, there is cracks between valves on all cylinders. I've read online it's ok. Not much worry about those.
But there is more crack, between one valve and the preheating space; present on three cylinders.
Pictures :
https://ibb.co/FnHx1gs
https://ibb.co/0B5FtGc
https://ibb.co/FX75TYJ

What do you guys thinking?


Second : One piston seems in a pretty bad condition, like if it has been gently smashed.

Regular one :
https://ibb.co/jZYCGZJ
Smashed one :
https://ibb.co/NTrfmNq
More pistons :
https://ibb.co/sFCdZgN

This is piston #4. Don't know what happened in there? No marks on the head, nothing.
Was thinking to file it and put it back?


Thoughts really welcome, thanks all :)

Those cracks are common. Usually not a problem UNLESS the crack extends to the valve seat area.

Not good. The next step in that progression would be for the prechamber insert to fall out. Resulting in catastrophic damage. I would condemn that cylinder head based on those cracks. :(

More than "gently smashed." :eek:
There may be further (hidden) damage to the piston. And/or to the rods.

Insufficent valve clearance? Dropped valve? Head gasket too thin?

Maybe, if you have no other resources. Would need to closely inspect the entire piston (especially around the pin area), and rod, as above. Could measure the protrusion above the deck at TDC and compare to the non-damaged pistons. That would give a clue to whether or not the rod bent.

Yeah, that was my thoughts too, thanks

May be.. Hopefully not, gonna take them off.
Well, I don't know about the valve clearance, don't think there was anything wrong it since there is no marks on the valve.
I think the thinner available head gasket was in (the one with 2 layers). Maybe, but again how come there is no marks on the head?


This might be hard to find any pistons, so it would be great if a could fix this one.

Thanks for your help