Are all MB heads the interference type?
 

Are all Mercedes heads the interference type?

If there are some that are not, is there a reference list somewhere as to which are and which are not?

If they are all interference heads, or for those that are, how often should the timing chain and guides be changed to prevent that pesky bent valve situation?

The models I currently have are 190E 2.6 (two of these) both with about 190k, 300SEL with about 190k, and a 420SEL with 130k and a dead engine (due to failure of a timing chain guide rail).

Thanks.
-Brett

Interference heads?
 

Yup! all of them.
Mike

interference heads
 

Great advice from the previous post. I just repaced all the chain guides, tensioner, and fron upper and lower oil seals while I was changing out the waterpump on my wife's 300 CE with 154K. I had purchased the car last year and it had a noise that I could not put my finger on...turns out to have been a chipped chain rail on the tensioner side. All back together now and the noise is gone. By the way, if you have an M104 engine like mine and remove the chain sprocket just below the intake cam to have the room required to relplace the guide on that side...remember that the bolt is a left hand thread and therefore loosens by turning to the right. I found out the hard way after stripping the hole in the head which I had to retap to 7/16 and make a new 7/16 left hand thread bolt to replace the old one since I could not find one anywhere. Beyond that, all went well and I am hoping that I am good for another 100K.

Antonino