I have a MM single row chain setup in my car (well, the whole engine was built by them actually). I take it up to 7700RPM all day long, no problems with the chain. The whole chain-stretching thing is a myth. No M42 owner has ever pulled their chain out after hundreds of thousands of miles and found it to have stretched by even 1mm. The failure mode is almost always that the rollers shatter and fall off (and get into the oil pump!), or just that the rollers wear on the pins and things get a little sloppy/noisy. Personally i have never heard of a broken M42 timing chain. According to MM, one of the big reasons that the M42 has such a bad track record with broken and worn out chain guides is that the OEM double-row chain is way overkill and all that mass swinging around just wears everything out. In their opinion, the single-row chain makes for a MORE reliable engine (and of course keep in mind that they also happen to sell this, so believe what you want). One must make sure to use a proper chain that is strong enough though.
To properly do the conversion, you need the chain, modified cam sprockets, a modified crank sprocket and a modified idler sprocket. Honestly, if you are going to bother at all, swap in a late-model M42 timing case, or an M44 timing case, since those do not use the stupid idler sprocket at all (it is VERY unreliable at this point and has caused total engine failure on many M42's by now). The M44 timing case uses a slightly larger oil pump, which is a plus, but you will need a custom bracket to hold the crank position sensor.
Topic: Single Roller Timing Chain (Read 3944 times)