I put a 13B rotor housing on my mill and took dimensions of the tension
 bolts and the other three bolt holes. I chose to call the top right hole
 hole zero and numbered them clockwise. The exhaust flange is on the right
 side and the plugs are on the left. I got these numbers:

 HOLE0:  0,0
 HOLE1: 1.5374 -0.7755
 HOLE2: 2.077 -2.6646
 HOLE3: 3.23 -4.5695
 HOLE4:3.2108 -6.6415
 HOLE5:2.1186 -9.4545
 HOLE6:1.0218 -10.3685
 HOLE7:-0.7378 -10.932
 HOLE8:-2.4868 -10.7575
 HOLE9:-4.0164 -9.9565
 HOLE10:-5.0822 -8.6915
 HOLE11:-5.6008 -7.2725
 HOLE12:-5.6270 -5.1825
 HOLE13:-5.5442 -3.305
 HOLE14:-4.8912 -1.822
 HOLE15:-3.688 -0.5975
 HOLE16:-1.7306 +0.1215

 There are two larger diameter holes 0.630 sized at:
 2.137 -10.7255 and also at -6.143-1.851
 and there is a smaller diameter hole at -6.913-10.822
 but this last hole is somewhat inaccurate.

 Zoltan Szakaly

I have included this picture of the rotor housing that I measured.
Hole 0 is my origin and hole 2 is the one that is missing on some engines.
The X axis is down Y is to the left on the picture.

Zoltan Szakaly

 The Rotary Engine News Letter. Powered by Linux.
  ACRE NL web site. http://www.rotaryeng.net
  You Tube http://tinyurl.com/beqqxas
  Copyright 1998-2013 All world wide rights reserved.