Modifications to Cast Iron Turbo Exhaust Manifold
 

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

Die grinder will make short work of it with minimal chance of digging,
gouging, slipping, etc. Not too mention skipping all the setup and
clamping.

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

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/

Boris Mohar wrote:
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

I don't know what a "TD05 Cast iron turbo housing" is, but if it got hard
then it was exposed to carbon and heat, and carbon dissolved into the metal.

GWE

I wouldn't change it at all, unless you have to. I would install a boost
pressure gauge and maybe an EGT gauge as well. They are inexpensive and
chances of the stock turbo overpumping is slim to none, considering how
conservative the factories are.
Steve

"GriffithBuilt" wrote in message
ups.com...
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

On Wed, 15 Dec 2004 12:55:31 -0500, Boris Mohar
wrote:

||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

I've done this a number of times on Buick GNs and a die grinder is the only
way to go... but...be careful to first mark the WG pucks contact area before
you begin to enlarge the hole.
More often than not, the puck does not close exactly centered over the
existing hole in the exh hsg. Usually you'll see a carbon track there on the
exh hsg to indicate where the puck hits it so grind an equal amount
concentric with that carbon track to be sure you don't get into an area that
the puck can't close off.
As for the carbon hardening the casting, though I'm a machinist and not a
metallurgist, I douldn't think that could be possible but repeated heat
cycles can work harden the casting which in this case is what I believe has
happened.
Thanks,
Steve Monroe

"Steve Lusardi" wrote in message
...
I wouldn't change it at all, unless you have to. I would install a boost
pressure gauge and maybe an EGT gauge as well. They are inexpensive and
chances of the stock turbo overpumping is slim to none, considering how
conservative the factories are.
Steve

"GriffithBuilt" wrote in message
ups.com...
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