That extra grooved main bearing

[fatmobile]

  I just posted this in the FAQs but am going to post it here too.
 Because I don't visit the FAQs often and am not sure others do either.

Hey, bumping up an old post.

As some know the main bearing sets come with 4 flat bearings and
6 with an oil hole and groove.

Well there are only 5 mains so that grooved bearing has to fit in one of the caps.
 
 I'm rebuilding an engine and while putting the main bearings in,
there is the old question of where the grooved main cap bearing goes.
 It seems like 2,3,4 and 5 mains supply oil to the rods through a hole in the crank.
 While #1 supplies no oil to a rod.
 
And I remember Jack, the former vwdieselparts.com owner and engine rebuilder,
telling me the grooved one goes on #1.
 
 I looked at the MK2 bentley page 41 picture of the oil passageways
and the idea that the #4 main bearing somehow supplies oil to the head
doesn't seem like any more than a rumor.

 It almost seems like VW intended for the rod to start getting oil pressure halfway down the downstroke
 and halfway back up.
 Before the flat cap bearing acted like a check valve at the top of the stroke
 to keep oil from being pushed back toward the main when it fires.

 I'm pretty sure I'm going to use the 2 grooved main bearings on #1
unless someone can convince me otherwise.