Quote:
Originally Posted by Assimilator1
I'm not an AE (just a car mechanic/tech).
But I would've thought that increasing No1 mains clearance would at best make no difference to bearing wear due to the chains tension, to at worst increasing wear (very slightly) as the oil film between the pressure/loaded side of the crank and bearing will be very slightly shorter and so (slightly) higher pressure/load on the oil film.
Would be interesting to hear what deansbimmer and other engine builders thoughts are on this.
Another point that most people seem to miss, twin timing chains used to be quite common in BMW engines (& others I'm sure), before they started penny pinching.
I don't recall their being problems with their no1 mains? Unless I just haven't stumbled across it?
2 examples of BM engines with twin chains are the S62 (e39 M5) & M57 (3 ltr I6 diesel).
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It may be because of the super long snout being unsupported. 2 double roller chains plus oil pump plus the harmonic balancer mounting holes/front oil seal area. I don't know if the newer lower engine pressure vanos creates more load on the timing system then the older high pressure vanos.