450SEL 6.9 Head Refurbishment

[MMWA]

For anyone interested, we are currently refurbishing cylinder heads on a 450SEL 6.9 due to an abnormally noisy valve train.

Nothing, and i mean nothing has ever made any difference to the noise, we have tried everything so this was a last resort.

Odometer reading 270,000Km.

Special hand built and complianced 1976 pre-release 450SEL 6.9 originally owned and operated by MB head office Australia, hand engraved markings on various locations on the drivetrain.

https://www.youtube.com/watch?v=eH-3I152_ek

https://www.youtube.com/watch?v=ng99JLlwVUM

Head Torque in WA, have done a number of M100 heads in the past, they are the go to place for anything with a cylinder head in Western Australia. They also did the head on my m104 it came out looking like a piece of jewellery and performing like brand new. They are not cheap but you get what you pay for. They are under instruction to deal with MB-Spares if they need any parts and not the extortionate dealers.

[brycedunn]

Nice videos, thanks for posting.
Never seen an M100 with the head off.

[MMWA]

There was also always a cold start misfire on one cylinder, till the engine warmed up and then the singer sewing machine sounds started. I think this is going to solve a lot of problems.

The noise is loudest at the second cylinder from the rear left - the one whose exhaust valve guide is totally flogged out.

The engine also always without fail when warm pings under full throttle. Timing is set correctly, tried multiple m100 ignition distributors and fuel injection systems. Adjusted and adjusted and adjusted. Nothing has ever changed it or made it go away. Will be interesting to see if this issue remains, there was not a lot of carbon in the combustion chambers.

Overheating exhaust valves is known to cause pinging in engines, and when the guides are flogged out there is poor heat transfer from the valve to the head for cooling. This is all VERY interesting and educational.

[Bartman4800]

About pinging: I know a lean mixture can be a cause too. I assume you are going to check all injectors for spray pattern while the whole lot is out?

I suffered from pinging with my Subi Brumby (I know, a whole different beast than yours ) and it turned out to be caused by low float level in the carb bowl (which was supposed to be tuned by a specialist...)

Bart