How To: Port the Exhaust Manifold

by Joseph F. Obernberger | March 25, 2005 10:42 pm

While having the exhaust manifold, and turbocharger off, I decided to attempt to port match the exhaust manifold to the head ports, and the exhaust manifold to turbocharger ports.  I decided that attempting to grind at the head couldn’t be done very well while the head was in the car.  To measure the port sizes, I took a piece of cardboard, cut out holes for the exhaust manifold studs, and bolted it to the exhaust manifold.  Then, took a sharp knife and cut holes into the paper where the exhaust manifold ports are.  I then unbolted the paper and bolted it to the head.  It turns out that the head ports (at least on my 1991 MR2) were slightly smaller than the exhaust ports.  That being the case, I decided to port match the exhaust manifold to the gasket.  As can be seen in the following picture, there is a good bit of lip from the gasket to the exhaust manifold.  It would be best to also grind the head ports to match the exhaust manifold gasket so that the ports on the head match the exhaust manifold ports as best as possible.

By using an old exhaust manifold gasket, a die grinder (air tool from Lowes $20.00), and some grinding stones from Sears, I ground the lip off of the exhaust manifold to match the gasket.

I did the same with the turbocharger to exhaust manifold ports.  Here I used an old gasket to match both the exhaust manifold and the turbocharger ports to the gasket.  I put rags into the turbocharger inlet ports to prevent dust from entering, and then used a shop vac to remove the dust.  In the following picture one of the exhaust manifold to turbocharger ports (left) has been ground, the other (right) hasn’t.  You can see the significant lip on the right hand port.  Without the gasket:
With the gasket:
Both sides matched to gasket:

I then ground the turbo side.

Source URL: https://midshiprunabout.org/mk2/porting-the-exhaust-manifold/

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