Used a cork gasket.. did i commit a sin?

Hmm. wouldnt you know. I just found my blue rubber gasket sprung a leak on a short highway trip. I actually looks like one of the corners split too.
suffice it to say I am not impressed. maybe I torqued them on too tight. I found some of the corner bolts on the valve cover had long threads on the and I had to tighten them on with a wrench. I didnt have a long socket in that small of shape. I guess I have diarreha of the mouth here but I had to tell someone :p

I have some leakage in the rear of the valve cover, as I understand it's common on this engine. Out of curiosity I looked over the gasket and it has the cork one, from the factory. Late '86 5 speed. Is this normal? Did the rubber gasket come later?

I don't remember exactly when but the rubber gaskets are much later, like after sometime after 88.

Also check the valve cover itself for flatness. They have been known to warp.

The F5xx part # on the updated ranger gasket indicates it was updated in 1995. It is pricy, like $40 from the Ford dealer, but, IMO, well worth the $$.