Cam followers can really only be checked by removing them and visual inspection. I've only seen it once. Drove me nuts looking for it though. On fllower had a chip on the very outside edge, and boy did it make a noise.

As you probably know the followers sit eccentrically above the lobe on the cam, the cam therefore spins the follower as it's lifting it. If a follower isn't turning they can knock, but it wouldn't be my first port of call.

Have you tried running the engine without the fan belt on it to eliminate waterpump and dynamo?

The other thing that may be worth checking is physical end float on the crank, If at some point it's been re ground it is possible to create excess end float by careless machining. Have a good tug back and forth on the pulley. Again seen it only once.

The final knock I've seen only once was a B18 with one rod which had been fitted back to front

Bottom line however is that these engines are extremely robust, it's much more likely to be something stupid and fairly readily accesible than deep in the engine.


Pete