On 15 Dec 2004 00:22:22 -0800, "GriffithBuilt"
wrote:

I have an old exhaust manifold for turbocharging a vintage BMW and I'm
running into a trivial difficulty with the wastegate flange. It's a
two bolt flange with a 22mm hole in the middle for the wastegate valve
to seat against. It's a leeetle small and I'm worried about boost
creep (engine getting higher psi than intended due to bad flow out the
wastegate). So I need to modify the circular hole to be around 32-38mm
in diamter instead of 22. Options obviously are use a flycutter to
machine it out or simply use an air powered die grinder (low tq, less
chance of mangling it) to grind it out after stenciling a template over
the existing hole.

Thanks for your time,

Jason

I had a similar situation with internal wastegate hole it TD05 Cast iron
turbo housing. I took it to a machine shop and they tried to drill out. It
did not work. The drill just spun there barely making a scratch. It appears
that part of the housing got altered over the years by constituents of
gasses passing through it. I ported other parts of this turbo housing using
a die grinder and had no problem. Finally I put a ball shaped grinding stone
in my drill press and loaded the feed handle with an elastic band. It took
some time but three stones later I had a 1" hole. I would appreciate if
someone could explain the process that hardened the wastegate passage.



Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs http://www3.sympatico.ca/borism/