I wish to bring this piece of information to anyone contemplating rebuilding their engine.

First I heard a small metallic noise like a bolt falling off from the body work [it does happen], the next time the sound was heard a closer look, much revving of the engine found nothing, the third time 'Bang' and the engine was sounding very sad, luckily we had just arrived at my works and I was able to wait there until the 'nice man with a lorry' could take Ruby and me home.

Once home, I set too. It turned out to be a failure of a small end bolt which was of the original type, I hadn’t replaced them thinking that they were fine. 

So the advice is this: if rebuilding your engine REPLACE the little end bolts [as if they were gaskets] the cost of the bolts is small compared to the cost of the damage!!

However please ensure that the bolts are :-

The correct grade The letter 'R' should be stamped on the head of the bolt which indicates a higher carbon steel bolt [stronger].

2. That the bolt is the full length of the thread in the conrod, this will mean a little bit of filling of the bolt to ensure that the correct length is gained.

Tony Leslie at Holmesdale Sevens was very helpful and informative on this matter.