Timing Chain age
 

I have a 1978 450 SL. Timing chain and all parts were replaced about 9 years ago, at 144,000 miles. I'm at 200,000 miles - how worried should I be about my chain?

Would think you would be fine till at least 288.000 miles, if you stayed on top of regular oil changes and maintenance.

Thanks! Maintenance has been regular, lagging a bit on the oil changes (about 10k between).

Thank you - always worried about that chain!

IMO, 10k oil change intervals are far too long especially concerning timing chain life. I suggest 5k or annual (whichever comes first) oil changes with filter to prevent timing chain stretch and piston oil ring clogging/coking.

Age will not hurt the timing chain mileage will; however, age will take its toll on timing chain tension rails/guides which can cause chain failure. Tension rails/guides should be replaced when they appear "beer bottle brown".

pull both valve covers and look at the plastic chain guides. the inner 1 on the lh head is the most fragile of the bunch. because of the way the chain runs, it's the 1st to break. any broken bits must be fished out of the engine. pull the lower oil pan and get the pieces. they can get into the oil pump from there or the new chain can jump if a piece falls out of the timing cover. seen it twice.

while the covers are off, turn the engine by hand to tdc on the crank pulley. there are marks on the cams and heads to line up. keep turning the motor until the marks on the lh cam line up. then, look at the crank pulley. if the pulley is PAST tdc 7 degrees or more, you need a chain, guides and tensioner.

Thank you so much for all your suggestions! I appreciate them. My 78 is my daily driver, so I want to make sure she keeps on going!

Doing that oil change today.

Wow no one suggested checking the timing chain stretch.

You could inspect the length of the chain that is visible as you roll the engine and take timing chain stretch.

On my 84 300D the timing chain is OK, but the long tensioner shoe had the facing worn and falling apart.

Did you read my post? It's been mentioned.