Resurfacing D750 Head Question

[Jesnell]

I am rebuilding a D750 out of my B7100. I took my head to a local engine machine shop for a valve job. The head is very flat but has some mild pitting so the machine shop guy thought it should be resurfaced. There are these puck like inserts in the surface of the head that mates to the block. The injectors spray onto the back side of these inserts. It looks like these inserts should be flush with the head surface but on my head they are standing proud a bit. The machine shop guy thought they were likely hardened and he wants to surface them so they are flush with the head. Should these inserts be flush with the head surface?

I'm a novice with diesel engines and would appreciate any insight.

Also, my parts diagram shows a head gasket and a head gasket shim. When I removed the head there was no shim on my engine. Is the shim always required or is this only necessary if you're compensating for metal removed from the head during resurfacing?

Thanks, Jim

 

[ShaunBlake]

Jesnell, this is a question the gurus will have to answer. I suggest you PM (send a Private Message to) North Idaho Wolfman and Service Dept Vic, asking them for their wise counsel.

From my days as a grunt in a NAPA machine shop, I would say that the inserts you describe should be flush, not proud of the head surface. But that was (oops -- my calculator won't display numbers that big!) a long time ago, and I never saw a diesel head.

Best wishes on a successful repair, and please keep us posted on the progress!

 

[North Idaho Wolfman]

All should be flat Including the pre-chamber plug.
The metal shim is for when you have a sleeved block.

 

[Jesnell]

Thank you for the reply. I will have the pre-chamber plugs surfaced flush.

If I had to guess, I would say I'm the first person to go through this engine since it was new so I don't think its been re-sleeved but I thought all of the d750 engines were sleeved from the factory. Sounds like my head should have had the gasket shim and I need to get one.

Thanks again, Jim

 

[North Idaho Wolfman]

The factory didn't use them, factory sleeves were flush so they didn't change the dimensions.
Depending on how much they take off the head you still might not need the shim, I didn't on mine.
Leaving it out will only up the compression slightly and there still should not be any valve clearance issues.

 

[MagKarl]

Is it pocked on sealing surfaces and causing a problem? I don't see how knocking down the inserts is going to buy you anything, it came that way from the factory, right?

 

[Jesnell]

The factory didn't use them, factory sleeves were flush so they didn't change the dimensions.
Depending on how much they take off the head you still might not need the shim, I didn't on mine.
Leaving it out will only up the compression slightly and there still should not be any valve clearance issues.

Ok, that helps. Thanks.

 

[Jesnell]

Is it pocked on sealing surfaces and causing a problem? I don't see how knocking down the inserts is going to buy you anything, it came that way from the factory, right?

The pitting is pretty mild but it is on the mating surface. Its not obvious that the pitting is causing any problems but while I have the head off I'd prefer to correct it.

I'm puzzled with the pre-combustion cups being proud. I can only assume that somehow they work their way out of their seated position. I can't believe the factory would have installed the heads with the inserts not perfectly flush with the head surface. I wonder if there's a way of pressing them back into position without damaging the head.