So, the right hand tapped cover is off, along with the intake manifold, and all but the front cyl on the right hand side, No:1 it appears, has a clean intake port and back of the valve and valve guide are like just been serviced clean

Under the tappet cover is also like it's just been washed clean

Checked the no:1 intake cam lobe was up, poured some diesel into No:1 intake port and it bubbled and quickly drained into the cyl ........ Loosened the cam mounts to allow it to lift a bit, the No:1 cam follower/rocker could now be moved a bit, poured more diesel into the port and it was still there a few hrs later .....
Clearly, there in insufficient travel in the hydraulic lifter to compensate for the valve stem height .... but unless the exhaust valve suffers the same problem, it should have been backfiring up the intake. Also, is that the problem with the other cyls with low compression?
If I make up a cyl leak down set up to put compressed air into the cyls, one at a time, with the cams removed and the timing chain cable tied to the cam sprockets, I need to make certain the piston will not be pushed down with the pressure turning the crack shaft and possibly causing the timing chains to jump a tooth. I'll have to see if there is a way to get the fan off and radiator shroud out of the way to see if I can get a socket and bar onto the crankshaft pulley bolt and tie that to the chassis rail .......
Next problem is, it that turns out to be the problem, someone did a full head service and didn't think to do the valve heights and that is what is causing this problem ..... how do I fix it without removing the heads?
To get the heads off, it appears as though I may have to remove the timing cover .... quite a task with the engine still in the chassis, radiator out, balancer pulley off and all the belt tensioners ... it is a one piece timing cover .....
Alternatively, I'll need to make up a method to grind the tops of the valve stems, square to the head, till I get all the valve heights correct .....
I'm not sure which job would be the hardest ......
A few beers and think on it might be the best choice for this evening
T1 Terry