Thursday, May 21, 2009

AE86 Tech #86-10: Street port

Porting is something most do it yourselfers rarely tackle. Most seem to think it's a daunting task to take on themselves. While others want a professional to do it, but don't have the $$$ to shell out.

Since I'm already redoing my oil puking cylinder head, it's time I did a little port work. I'm not a pro, but i've experimented enough to take on this project myself. It's what I call a street port, since it'll be nothing close to what a full race port should be. If you want that you should give Hasselgren a call for the ultimate in 4AGE porting jobs. The street port entails the smoothing of the imperfections in the ports so that airflow is not greatly increased, but has more of streamlined flow into the cylinders.

You maybe thinking since i'm turbo i don't really need to do this, just crank up the boost and bam more power. Think of it this way, by adding a wedge in front of a brick like the battle wagon (Volvo 740 wagon) to streamline the airflow, you can increase the top speed and fuel efficiency of the car without upping the power output.

Anyways here's some areas that do it yourselfers can work on.

There's the traditional port match to the intake. Use the stock intake gasket as a template for the cylinder head and intake manifold. I believe certain racing groups like SCCA allow this type of porting to 1 in. from the flange surface. This should be a no brainer on how to do so we'll just move on.

The areas behind the valve seat usually have ridges that should be removed. If you have a cylinder head apart, run your finger around that area, and you'll know what I mean. It's a speed bump for air molecules, bumping into each other as they enter the combustion chamber. Clean up the area by removing the ridges until you can't feel the ridge.

Another area to look into is around the valve stem guide. You can see there's 2 little bumps on either side of the valve guide. Some maybe a bit sqeamish about entering this part of the port, so just leave this area as optional if you're not comfortable.

As you notice the areas I have previously mentioned are now cleaned up resulting in a more efficient flow of air into the cylinder head. I didn't take too much material to alter the port velocity of the cylinder head. Not too bad for a nights work. Now it's off to the machine shop to get the rest of head machined and ready for installation.

Well that's about it, at least for me. Anything beyond that we're taking about changing port velocities and flow rates. A steady hand and eye to is needed to keep the ports equal. A flow bench to make sure that flow rates are consistent between cylinders.

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