Hello everyone.
After ten years of ownership and basically trouble free driving, my '69 280 SL blew the head gasket after a spirited drive on the local freeway. I removed the head, had it gently planed, replaced the gasket and put the engine back together. It was my understanding that they were not a lot of miles on the motor owing to a recent rebuild when I bought it, and I have not put a significant amount of mileage on in my time of ownership. The car has always run beautifully, so I didn't do the valves or the guides, just the head gasket.
When I started the car it ran nice and quietly at idle, but as soon as I revved it up a noticeable clatter started in the engine. It sounded like valve clatter, and when it did not just go away like it was supposed to I turned the engine off, let it cool overnight, and adjusted the valves again. This did not take the clatter away. I checked all the valve springs for cracks or breaks and did not find any. I checked to make sure that the TDC marks on the crankshaft, cam and distributor were still lined up, and they are.
After a great deal of head scratching and what not I finally determined that I had play in the timing chain at the tensioner sprocket. I removed the tensioner to see if I had assembled it incorrectly but I had not. However, even fully extended it is not taking up all the play in the tensioner arm. There is not a lot, perhaps the thickness of a thin slot headed screwdriver, but obviously any is too much. When I move the tensioner arm and sprocket back and forth with my fingers I can hear an audible metallic clicking that I suspect is the sound I'm hearing when the engine is running.
All of this leads me to believe that I need to replace the timing chain. This in itself doesn't seem that daunting a task, but then I get reading about cam shaft shims and all sorts of horror stories that neophytes like myself have unwitting launched upon themselves, so I am simply asking those who have been there before is the timing chain the likely culprit in my case? Should I measure anything? Count anything? Is there a timing chain God that I should pray too? I realize all of these inquiries might be a little bit like closing the barn door after the horses have fled, but such is the place I find myself in.
I'll answer a couple of obvious questions.
I did not overheat the engine before the head gasket let loose.
The head was not warped. It felt smooth to my touch but the aluminum was not mirror like shiny.
I have driven the car since re-installing the head and the noise if anything gets quieter under load. The head is sealed and the oil and coolant are not mixing. I have gotten it hot enough to torque the head to the final specifications.
I can easily answer any other questions that anyone might have.
Any and all advise would be greatly welcomed at this point.
Michael
