With the first head off I could check the piston bore and yes they are 86mm - so big bore.
The cylinders are cast iron, and given that I was given a NPR big bore kit box with the parts with the car, I'm pretty confident that is what is fitted.
Now there seemed to be quite a bit of oil in the bores, and the head was a bit oily black, which seemed a bit extreme for <1000 miles of motoring.
My first thought was that the head valves weren't properly sealed so I tested them with brake cleaner.
I did a cylinder at a time, here is No 3 holding brake cleaner indefinitely, as did No 4.
Both intakes and outlets are fitted with valve seals and they all looked fresh and good so still no smoking gun.
Time to keep digging.
I dropped the valves out of the head and all the valves are ATE.
The inlet valves for 3 and 4 were both oily black - urgh!!
Keep digging.
I next removed a cylinder to check the state and orientation of the rings and soon realised the ring gaps weren't in the most ideal places.
At this point I took the decision to drop the other cylinder head so I could pull all the cylinders.
The cylinder head of 1/2 looked similar although on this side there was no blackening on the inlet side of the inlet valves, so this side was better.
It's never good to see all your piston ring gaps have aligned! - this is cylinder 1
Here's a diagram showing how all four were.
You can see why cylinder 3 and 4 were particularly bad - cylinder 3 couldn't really have much worse orientation.
So annoyingly I think someone did a good job of rebuilding the heads, fitted a NOS NPR big bore kit, but don't seem to have set the piston ring alignment correctly.
Time to take stock with regard to the piston / cylinders.
