Hi if somebody can't help me. I have a 1990 range rovercounty 3.9. I bought it with cyl #7 deadno compression,took the heads out and #7 had intake valve seat pulled out and no damage to piston. Then I send the heads to be repaired at the machine shop.Then i put new timing chain and sprokets with the repaired heads and gaskets. I start using the rover but it lacks of power ,i check the compression again and i have more than 155 psi in every cyl. But i found spark plugs 2,4,6,8 clean and i mean white compared to 1,3,5,7 that have a nice brownish color, the thing is if i touch the exhaust manifold from 2,4,6,8 side is cold to the touch compared to the other side manifold that wiil burn your hand right away. Today i try swapping both o2 sensors nothing change ,a friend told me that if right catalitic converter is clogged it could be my problem. Another thing is that i try pulling out fuel injector plugs from 2,4,6,8 and nothing happened but when i pulled 1,3,5,7 the engine start misfiring. Sorry to be this long but i ran out of troubleshooting ideas!

 

Sounds like you may have a coolant leak on the right bank.
Might want to do a pressure test on the coolant system.