10/40 TOO thin.
Use a thicker oil, I use SILKOLENE PRO S, which is a 10/50, ESTER OIL, and then tell us the noise has stopped after a run!!
I take it you were impressed with the group a coil then!!, pity ford did not fit these to start with, you can also open your plugs up to around 0.9mm. now as well for even better running.
I bought my oil from OPIE OILS on here £40 delivered, well worth it.
tabetha