I have a photo somewhere....in South Africa in '91 we were trying to undo a 47mm bolt on a set of discs. All the heat and persuadin' we could offer didn't budge it, so with a combination spanner the ring end went on the offending bolt and the...

Try Gratech in heybridge

Probably a broken chain?

It depends what drives the oil pump ?

Bad connection to chassis or starter motor shorting out internally

Has it had a head gasket replaced recently, and its contamination that wasn’t cleaned out at the time?

If its still got the original inlet manifold gasket, that can leak oil into water