Anyone know why Ford changed these from both halves grooved to one grooved and one plain on the later RS Turbos?
Burtons sent me the wrong ones (both sides grooved) for my 90 rst years ago and it's a p.i.t.a having to buy another new set.

 

I don't know but can only guess it was to get better oil distribution across the journal, the shell without the groove acting as a wiper to spread the oil faster/ more evenly or?