Reading between the lines, did a spark plug break off in situ, and whilst drilling it out the drill broke leading to bits of broken drill and spark plug being lost inside the engine?...then the engine was restarted?

If so, you don't need us to tell you that the engine should not have been restarted, the camshaft and/or head should have been removed and all broken parts found, jigsaw style, then reassembled.

All you can do now is remove the head, and fully strip it for inspection.

alternatively, is there any chance parts could have ended up inside the combustion chamber?...if not then it *might* be possible to remove the camshaft(s) leaving the head in situ, and after buying a suitable lens feed a tiny camera down into the plug hole to inspect for valve/piston damage, together with compression test.

You must be absolutely certain that debris could not have got into the cylinder, it couldeasily have become wedged down the side of the piston and still be there, that will wreck the engine completely, hence why head removal is the best bet.

I'd be DIYing this, Toyotas are usually simple enough to work on.

Edited by gordonbennet on 25/05/2014 at 11:58

The broken drill bit was inside the chuck at the time unknowly and was using the drill to remove bolts and broken bit fell under cam shaft accidently, possibly under springs causing the noise, but there is no way of identifying where this bit has gone, more likely to the back and more possibly on the exaust side the broken spark plug was over a year ago and prusumed it had shot right through to the exaust side of the piston, but it is the wrong side too where this sound is coming from, but not like this, colour of spark plugs are all the same grey carbonindicating there all working the same. But have just performed an oil changed before this noise was louder, so maybe indicating something has moved on top of the head at this point I am confussed where to look at this point apart from taking the entire head off!