Thanks for the responses guys,
Russ, you are quite right about the about the slight lack of power on WOT. My car is also showing signs of this so it would point to a lack of fuel getting through. I purchased a thermal barrier for the carb and this has indeed cured the problem of heat transfer from the manifold to the carb. I found it odd that on the Edelbrock packaging it stated that the thermal gasket was "not for road use!". Why I don't know, it sorted out the problem though.
The misfire is intermittent and seems to be more evident when the engine is cold, and put under load. However, then it can also happen when it is warm and just going along at cruising speed. Weird, and I have tried to check all of the usual causes.
Jim,
The carb was new and fitted a few months back. The misfire has always been there but has got worse in the last few weeks. It does get worse when the car is under load and in the lower rev range. If you put your foot hard down it does seem to power through it.
Trevor,
I think you may be right about the pressure gauge not being spot on. I have just had a go with another one and the reading is different again.
I have reset the pressure once more and installed another rotor arm on the distributor. The last one was not a genuine Land Rover part and I know the copies can sometimes be troublesome. I am just going to go outside and take her for a test drive. (I really should be working, but thats the advantage of being self employed!!)
Thanks for the help once again guys and I will let you know if this makes any difference.
Regards
Simon