||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.
Turbo manifolds are often made of cast steel. They get a lot hotter and carry more weight out at the end than regular manifolds. Texas Parts Guy