i have the noise from cold and at idle and when its reved but its the same sort of tail off revs at about 3500 when i cant hear it any more.im thinking im just gonna change the block as ive got a couple spare as i heard today that it used to be quite common for the cvh block to crack internally between oilways ,its just one more thing to try i suppose.
thanks for your help i'll let you know how it goes