cam chain tension
 

I've read the threads and this has come up before. But I don't see why the regular spring loaded tensioners are not appropriate for setting a consistent tension for cam timing. We seem to go to a lot of bother to come up with a range of mechanical tensioners - to accomplish what function that the engine tensioner can't perform? And wouldn't the engine tensioner be closer to the actual tension the cams operate on?
I ask this after just having spent half a day making a RH tensioner.
Thanks
Alan