1500 JB problems

Hi guys,

I changed the cylinder head on my 1500 JB engine due to snapping a tap in my original one The new head came with a weber 36tlp and since getting it on it just wont run properly.
Changed all leads, plugs, dizzy cap and rotor arm and the coil. Car is on powerspark electronic ignition.
I've set up the static timing properly, all marks and notches line up on pulleys, flywheel and dizzy.
However, once car is at idle, pulling cylinder 3 and 4 ht leads, there is absolutely no change to the engine, indicating it is running on 2 cylinders Compression tested all cylinders, they're all rather low at around 130 psi, but no major difference between any of the cylinders.
Am I looking at stuck/damaged/burnt valves?

Any help would be greatly appreciated.

Thanks,
Matt