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Porting?

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Port and polishing heads is like an art. Its not something you would want to do to your bike with no prior experience. I would read up on how its done, and then practice on some old busted motors. Not to many can do it properly, cause like anything it takes time and practice to get it right.

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Dave Miller of Miller Racing Engines in Everett Wa did mine. He just did a slight MX port. It is to enhance midrange power. The change was very unobtrusive on a stock engine. Combined with a cam and more compression the bike runs very well. You will need to send him your head, a used exhaust port gasket and the untake spiggot.

Give him a call. 425-335-0466....tell him Diesel Freak sent ya!!

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Porting is more common sense than art. The air is a fluid that needs to go through with as little resistance as possible. That being said, there is more to smooth flow than simply making things bigger. Just like a river, there can be undercurrents and eddy currents that foul up flow. You can make these problems just as easily as you can do anything to increase flow.

Don't allow your airflow path to "jump" over anything in the port. This usually means that you leave the bottom of the port pretty much alone and just work on the top. That is an oversimplification but has been pretty true on most motors I've ported. I've ported several sets of racing heads for Buick V6 motors (iron and aluminum). The easiest thing for anyone to do is a port match. That's why he wants the exhaust manifold. All that entails is removing all port material that overhangs the exhaust / intake gaskets. On the exhaust, it's easy enough to just remove everything along the port circumference that is black as you look in from the exhaust pipe side. On the intake side, there's no gasket. I just started working slowly, removing some, then putting it back on till the match was very close.

You can always streamline the valve guides and remove material in the valve bowl area to the valve seat. This is usually the biggest gain and is called pocket porting. Just be sure you protect the valve seat. There is no allowance for nicking the valve seat surface. Several layers of masking tape work fine though.

When done, smooth your handiwork with a sandpaper roll cartridge till it's all blended and smooth. The intake port can (really should be) a smidge rough. The exhaust port can be mirror smooth. You can also smooth the combustion chamber surface nice and shiny. Remove any sharp edges with your sandpaper to prevent detonation.

I'm going to backcut my valves if / when I pull my motor. Makes them lighter and flow better. I've port matched my intake and exhaust ports with the motor still in the bike. It's pretty easy to do and takes very little time. All you need is a die grinder and a carbide cutter. Use a double helix cut on aluminum or it will load up. If you dip your single helix cutter in transmission fluid first, it won't load up for a bit but you must keep re-dipping.

I posted a couple of pictures of my exhaust porting a while back. Search for them.

Roger

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I think I've seen it offered for around $200.

BTW, I am not soliciting for business. I don't port professionally, I've only done heads for my friends and myself. I've never ported a bike head beyond what I've described above.

It's one of those things that you THINK you can't do. Once you do it, you'll realize it is neither tough or difficult. Less is better than more though. If you were close, I'd show you what to do.

Another thing. When people talk about a port job to tailor an engine all they're talking about really is what they do with port volume. Smaller port volumes tend to produce high velocities and torquier curves. Large port volumes should be matched with more cam duration / lift to take advantage of the increased area for the airflow. That allows max airflow but the velocity suffers a bit in the lower RPM ranges. It's more of a top end motor. You actually are tuning the motor for a specific RPM range. A big port with a short intake valve event would hurt cylinder filling and be more prone to the gas condensing in the air.

Thumpers are for torque IMHO, I'd never hog out the ports at the expense of mid range power.

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