Quote Originally Posted by bozzer View Post
Now I'm starting to doubt myself.

Looking at the video again there is absolutely no evidence that there has been any pins in that groove on that nose of that rod. I'd expect to see something where a failed pin had started to go and some wear around that groove. There's nothing.

I know little about pressure bonding. Could those two large pressure 'crimp' dents put enough pressure on the steel head that part of the inside diameter of the head where the rod fits in is forced into that turned groove on the piston rod? Just enough so that it holds the piston rod in place. On the wobbly pistons there's been enough wear to give some movement but not enough for that ' pressed in ' areas of the inside of the head to let go of the piston and allow it to come out.

It's an easy option re manufacture. You don't have to accurately drill/mill holes in the head for pins or make/buy pins and fit them. You just allow one high pressure crimping action hold the piston body to the head and the head to the rod ( the latter via that turned groove ).

PS ... I think gc93 beat me to it whilst I was typing. Well done gc93 ... that's now my favourite option.
Now I''ve read that I may have to agree with the both of you.

As the crimping causes the piston to go slightly out of round (and yes it does) would any out of "roundness" cause pressure points to try and force the piston back "round " and thereby loosen the effect and integrity of the crimp ?

Given that the suggestion is that the crimp may only just retain the rod, I think this is highly possible

I for one take these high points off on all mine so hopefully no issues