L Series Non starter post rebuild

Hi everyone,
I was after some advice regarding a L seres engine that refuses to start!

To give you the history:
Turbo oil seals failed, suffered 'running on' stalled engine before destruction.
Turbo replaced, engine ran but rough.
Tried easy things first, injectors, timing etc no effect removed head.
Upon inspection #3 piston crown melted, rings buggered.
#3 piston assembly replaced, other pistons and cylinder block examined- ok
New head gasket, head refitted, all ancilaries refitted and timing correct for all aspects
Engine turns over, glowplugs working, lots of fuel being injected- no combustion!

I was present for all the work except fitting the cylinder head which was done by my friend. The engine turns over far 'Too Easy' in my opinion, by hand and by starter and I think it is lacking compression. Also when turning over the crankcase breather on the rocker cover is 'Puffing' very frequently. Cooling system is not being pressurised by the cranking.

My friend had stored the head in his shed and by his own admission, "the valve seats were a bit corroded but I'd thought theyd clean up!"

So what do you reckon people? Head off and re-grind the valves? I had someone else suggest easy start to get it going but am reluctant to use that stuff.

Also, there is no oil pressure light coming on at all, removed the plug and tested with multimeter and there is no feed down to it. Bulb gone? or something else management wise?

Thanks in advance for your thoughts,

Nothing to do with starting, but have you checked every bearing in the block? If ithas run dry then you have screwed all of them. If it has over-revved then it could have destroyed the timing components as well.
And yes, dont do half the job, take the head off and ensure everything is as perfect as it can be. Or do you want to do it all again?

Thanks MHM,
The bearing shells were all fine and the engine rotates nice and smooth. My mate was quick in stalling it, so still had lots of oil left
My thoughts exactly, I wish he had mentioned it before as I certainly wouldnt of refitted to head with the seats corroded, oh well head off and get lapping!
Thanks,

Well, its a diesel and it compresses that air down to 1/20th of its volume. But you can turn it by hand. Sounds like its not very air tight in there. Head off again me thinks.

Keep us posted with this, interested to hear what come of it.

if you melted one piston have the rings got hot in the others so they have lost their springiness, if you squirt some oil into the bores do you then get compression, is the timing correct or 360 degrees out

Quick update:
Removed head tonight, pistons and bores look fine, put some oil in the bores to see how tight the ring fit is and the levels havent dropped, happy days.
I disassembled the valves and upon inspection several valve seats, particulary the inlet seats, are corroded where the head was poorly stored.
Hopefully lapping in the valves will do the trick, and get me some compression back!

Thanks for all the suggestions so far, top notch guys,