J,
I've attached some info for you to determine what you'll need to replace. The instructions attached are for the 278 engine, but provides the validity for all engines in the 231 chassis. I can't attest to whether you'll have to remove the intake manifold. Read this PDF for the 278 V-8, and get an understanding of it. I would speculate it's similar to the 276 V-6 engine with the 40° crank position info (read PDF), you'll need to get specific directions to perform this modification on the 276 engine. Tech told me if you don't follow the 40° crank position, overlap instructions, you'll snap the cam shafts. My 2013 SL550, I sold in Jan. 2021 with 21,000 miles on her, and about a year and half ago I thought heard a slight chain rattle on a cold start. According to the paperwork my engine number fell into the category of requiring both tensioner and check valves.This was why I gathered this information. In all honesty, I may not have heard anything, echoing off the garage walls, inside the car with the windows closed, it was hard to tell. I never experienced it again. The 278 engine is quite loud on the cold start. My tech friends at the dealership said that if you don't hear it all the time, don't do the modification. Tech explained it's not like an old 117 motor that jumps time and destroys the top end. It's just a slight bleed down on the tensioner or check valve which as soon as oil pressure builds it's fine. However, I prefer not to have any chain rattle. Good luck, keep us posted.
Thorgod
