Quote Originally Posted by spike076 View Post

1. Locate where the noise is coming to the closest cylinder and disconnect that spark plug lead. Start engine and see if there is difference in noise. If so then it would suggest main bearings.

2. Remove serpentine belt or main belt whichever you have and start engine if noise is quieter then this would suggest big end bearings.
I think the cause and effect might be back to front in your explanation - shorting a plug on a suspect cylinder should make a big-end bearing go quiet.

I had this problem on mine but the worn big-end sounded more like a tappet noise, than the usual deep knock I am used to. I made up an attachment which was a piece of 3mm welding rod soldered onto a high-tension lead clip, which was then pushed on to the plug and the other end fitted into the HT lead. Whilst the engine is running the plugs can be shorted with a screwdriver to see if the noise goes away.

I hope it goes well for you and is just an exhaust noise,

Cheers Charlie