[T2] Identifying bearing sizes

[John Anderson]

Monty,
 
The 0.25 indicates that they bearing is 0.25mm (which is roughly 0.010") thicker than normal for a crank ground "10 under."  Some bearings over the years will mark their oversize for the case if present on the shell as well (but actually not any OEM T4 ones I have seen, but I've been out of the building engines frequently game for 15 years.)  You can pretty well presume though as you figure on most T4's indeed they probably haven't been line bored, and probably don't need it if on the 2nd, or even 3rd build.  Looking for "fretting" around the bearing saddles and through bolt locations will give you a good idea of the need, measuring a tightened case with a bore mic will give you a better one, and dropping in the crank with new (appropriate sized) bearings and Platigaging, all 4 bearing locations simultaneously is always needed and will give you a good idea things are in line concentric as well, but if you don't like those results you have wasted
 money on a set of bearings.
 
Now of course you can just buy the same 0.25 set if you are going to hope to polish and re-use the crank, (may be doable) but if you are having it ground or going with a regrind from somewhere else (usually some good samba deals, particularly on 1700/1800 cranks), you got to buy appropriately.
 
John
 

________________________________
 From: Monty Rowden <montyrowden at yahoo.com>
To: type2 at type2.com 
Sent: Thursday, January 9, 2014 3:38 PM
Subject: [T2] Identifying bearing sizes
  

Hello all.  How do I know what size my case has been bored out to upon disassembly of my engine.  The center main bearing is the only one with numbers on the backside of it.  And it says .25. Is this what the crank was turned at or the case.  It is a type 4 case.  I realize not to many type 4 cases need to be line bored.  Just need help identifying.  Thanks!