Hi Coxy Thanks for the reply.
Did you have the same sort of symptoms running up to the rockers going?
How did they go on 2 occasions? i've not heard it as a common issue...
The first time was very shortly after I purchased the car, I always thought it sounded a bit tappety but put it down to have 4 more tappets than my 1.9 156. One of the centre pins came out and chucked the needle roller into the sump. On that occasion There was no noticeable lack of power, but that said it was only one rocker which had not at that point snapped it was just all the oil pouring out of my oil pump casting where the needle roller had gouged through.
On the second time the car was losing power, would not rev and would not make any boost. This got progressively worse as more and more rockers failed as the engine couldn't breath, until in the end the engine died.
I think to be honest I was just unlucky and had a bad batch to start with. I was then my own worst enemy as for some unknown reason I did not change all the rocker, no one else to blame but myself as I do my own work.
The rockers are designed to break if the piston hits the valve in the event of a cam belt issue in theory reducing the damage to the engine. On inspection of my failed rockers it would appear that the centre pins had been pushed / crimped off centre.
I don't know how common a rocker failure is without a cam belt issue but from what you have described it sounds very like a rocker, lack of power revs and that noise. It could also be a swirl flap has come loose and is sitting behind a valve, but having no experience of that I don't know what noise it makes.