Few threads on it, remove inlet manifold and remove each bolt which holds the rocker cover on and put some gasket round they'll of the bolt and then put it back in. Do it with the few bolts u think may have caused it to leak. One will be allowing oil up.didmine few month back,took an hour and half not leaked since. Having a new rocker gasket is a big and expensive job. I used wyns black gasket its about £20