I see the forum doesn't embed videos, but it is on Youtube here:- https://youtu.be/QzepMKYsg24
After gradually stripping the motor and with a hint from a University Motors video I have identified it as the number 1 con rod clipping the camshaft. I don't know why but I have determined from receipts I got with the car that it had suffered a dropped valve in that cylinder and had a new valve and piston installed. It had a crank grind and new mains/big ends and oil pump fitted as well.
I've taken the that piston and rod out and find that there is a witness mark on the cam and the shoulder of the rod. Only that cylinder and only on one side of the camshaft. With the crank turning twice to every cam turn I would have thought it may scuff both side of the camshaft.
So, do I just grind back the shoulder of the rod? Do I need to balance them (bearing in mind a rod/piston weighs 1 Kg).
I am putting a new cam in anyway.
![Image](https://i.postimg.cc/G2n5LLnz/Cam-damage03.jpg)
![Image](https://i.postimg.cc/660mKxjL/Cam-damage01.jpg)
![Image](https://i.postimg.cc/rmTf6f5P/Rod-damage01.jpg)
![Image](https://i.postimg.cc/Jzy6jD1P/Rod-damage02.jpg)