Lynn,
I have a '90 13B engine that I am rebuilding (not for aircraft use, yet).  I rebuilt an '87 engine and had the cast iron housings
commercially lapped.  For the '90 engine I would like to know if there is a do-it-yourself way to lap the housings to just
take off enough material to flatten them without getting into the nitride any more than is necessary.
If I recall correctly, the commercial lapping house said that they had to take off a set amount even if
it was more than the minimal amount to flatten the housing. One other question, what do you do to prepare the rotor housing before a rebuild.  Do you lightly scuff the surface or not?

What do others on the list do for a rebuild?

Thanks,

Jim Brewer
Albemarle, NC