Background: This is another one of those little tricks where a part from one of the newer BMW models happens to work very well on our older E30 M3 cars. In this case, the part is the timing chain tensioner from the E36 M3, both the early U.S. S50 as well as the later 3.2L Euro S52. It may also have some application on other BMW models. A table of applications for the BMW E36 M3 is shown below:

As far as I know this particular mod was first talked about on the " Roadfly " message board, and came to the U.S. via one of the European E30 M3 enthusiasts. I was quite skeptical about it at first, but then Jimmy Pettinato bought one. He told me it worked great and we spoke about some of the ways it was different from the standard S14 tensioner. This convinced me to buy one and check it out.

Details: Everyone who has installed one of the S50/S52 timing chain tensioners in an S14 remarks on how quite the engine is upon startup, a time when the S14 engine is known to produce a lot of timing chain rattle. The explanation I always read is that the E36 unit does not have a spring, and therefore the timing chain rattle on startup is reduced/eliminated. This is a bit of a misperception, since before the oil pressure has had time to build up the spring is the only thing providing any tensioning force on the chain. Without a spring the S14 would make a heck of rattle on startup 8^)

Careful observation of the S50/S52 tensioner reveals that it certainly does have a spring, it's just that the spring is "pre-loaded" within the tensioner. This makes the tensioner much easier to install, as you do not have to compress the spring manually while at the same time trying to line up the threads of the tensioner with those of the cylinder head. Once the S50/S52 tensioner has been screwed in to specific point, the tip of the tensioner contacts the back of the tensioning rail. As one continues to screw the tensioner into the cylinder head from that point on, the spring starts to compress and bear against the tensioning rails.

Now Jimmy thought that the reduced rattle upon startup might be due to the E36 tensioner having better tolerances (so that less oil leaks past the piston). However, in my own comparison of a new S50/S52 E36 M3 tensioner to a factory E30 M3 tensioner with about 5000 miles on it, I could detect no such difference. In fact, if anything, the tolerance on the E36 unit might have seemed a tad looser.

However, it is not my nature to simply accept that something is better without knowing why. So the investigation continued as seen on page 2 »