thanks ill have a go a testing it that way. originally thought it might be the big end, pulled the sump off, big ends had some wear but nothing extreme. checked main bearings 1-4 (the ones i could get to and they were fine) cylinder bores were fine as well no scoring or damage. car runs fine, no loss of power and doesn't blow any smoke. still makes the noise with all the belts removed and its not the harmonic balancer either. i did pull the vacuum pump off and the spring and everything internal seemed intact. pulled off the rocker cover as well, one of the valve caps was starting to get hammered flat, but everything else such as pushrods and valve springs etc are all fine. just waiting on a set of big end bearings and valve caps to arrive and ill put it back together to a stage where i can get it running and ill try the vac pump again.
will keep you posted
