Finally, I think I've got it sussed.
It seems to have been a collapsed lifter causing my problems.
I didn't quite understand how they worked until someone explained it and I realised that the intake had been trying to open the valve on very high pressures and this had obviously damaged the non return valve (in my stupidity I thought because I couldn't compress the lifter easily, it was ok) I stripped the intake off again and removed both lifter for no5 cylinder.
Sure enough after cleaning them of
oil I was able to blow backwards through the intake lifter.
I'll get a new set tomorrow.
Thanks for all your help, please pardon my ignorance.
Simon
Have a happy Xmas.
