On Feb 25, 2006, at 5:03 PM, Lehanover@aol.com wrote:

In a message dated 2/25/2006 6:49:45 PM Eastern Standard Time, crayd@cableone.net writes:

I bought this pair of used rotors to build up a new motor so I can retrieve my RV-6. They look different in the compression chamber "tub" area, otherwise they look identical. They both are marked "D" for the weight code. Can anyone identify these and verify if they are OK to use ? I am thinking if the compression ratio is different, it may run rough even if they weigh the same. I remember Ed posting something about a way to measure the depth, but I cannot find it in my sea of saved emails.
 
Chuck Dunlap
N616RV 13B

Chuck they are definitely different CR, as they are from different years across the split where Mazda increased the compression ratio. The fully machined rotor depressions are 1989 or above. The partially cast rougher depressions on the rotor on the left means it is 1988 or newer, therefore a heavier weight and lower compression than the rotor on the right with a machined face.

Hans