1984 380SL Timing Chain Question

[rockcrusher]

While I was checking my timing chain stretch, I noticed that the chain tension between the cams would changed as I rotated the crank. I would be tight until I approched the cam marks, then it would go limp. I know it's time for a renewal of chain and rails, but what's odd to me is I can just touch the upper cut-out of the head when it's loose, ( it just started to make contact), but it is just snug tight the rest of the time. Just currious if anyone else has experienced this???? Thanks, Tom in N/E Michigan..

[david s poole]

that is being caused by valve springs pushing back up and moving one camshaft around a little giving a loose chain feel because the engine is not running and the tensioner is not pumped up by oil pressure.