doing a rebuild on a td42. need lots of advice please

[BigRAWesty]

Well you have a lot to chew over..

First up pull the donk out.. I'm sure somewhere in the manuals there would be tolerances for such things like sleeve and piston wear. If there within spec then its up to you with how much you spend, full kit or just rings.

You say your down on compression but have you been able to isolate if its going up or down? (threw rings or past valve)
Not sure how you can tell, ill ask my brother.

As for the turbo, should be fine running the psi you want, and same with the pump. Price a newer GU pump and compair with an overhaul price. You might find a good GU pump second hand cheaper than a GQ pump rebuild kit..
If you do go the GU pump try and grab one with the compensater. This gives you optimum air to fuel ratio threw the rpm range..

Apart from that, valves.. Yea if the issue lays with them. Doesn't hurt to have the seats ground, but its just extra if not needed..

I'm sure I've missed something.. I'll let you know what my brother recommends checking in regards to the blow by..

Enjoy the build..