exhaust ports Pro Comp Cylinder Head

Best Tools Cylinder Head Porting

Best Tools Cylinder Head Porting

Been a while since I had time to make a post. I wanted to help everyone with a few mistakes that cost the most money when porting cylinder heads at home. Best Tools Cylinder Head Porting are the ones that work for the jo job your doing.

A good bool to read is four stroke performance in theory and practice by A. Graham Bell Here is a link to find it on amazon.

Amazon: Four Stroke Performance Tuning


This book is a general reference and helps get the idea of what needs to be fixed to increase air flow and make more power. Some reference material on the type and model head you will be working with will be best for detailed information.

Tooling: Best to use a tool like these from Foredom
 they will last and can be repaired when they wear. This one is designed for aluminum mostly and may not last as long if used for heavy cast iron porting. But does provide the best control with cable driven head and foot pedal activated. At the very least you will want these types of cable driven tool for porting.

For heavy cast iron its best to have a heavier tool. Many people use heavy electric die grinders that work well. Air tools are OK for some cast work but they stall and do not produce the best results. For aluminum heads I recommend you do not use air tools. The loss of control will cause the bits to dig and cut too deep all at once and can damage the head beyond repair.

Cast Iron Heads


Cast Iron Heads: You need carbide burrs with cross cutting pattern. Its best the bit should be of good quality. These will last longer and allow you to work with less chance of the bit grinding to a stop or digging too deep. You will probably need long and short bits.

Long bits are ok for deep areas of the port but have more flex and can be hard to control in the short side of the head where control is most important. For cast iron heads you will also need stones and sanding rolls but most of your work will be with the carbide. Also be sure all tools are made for cast iron work.

Aluminum Heads: Carbide burrs can work well with aluminum heads but eat metal very fast and can trash a head much faster than working with cast iron. Be careful to dig from right to left against the rotation of the bit. Making smooth controlled cuts until the you have the desired shape. You can not use stones with aluminum. But sanding rolls and flapper do well.

Most of the time sanding rolls and flapper will be done as finish clean up but will consist of the most of the work. For aluminum heads you will make only a few cuts with the carbides and most of the clean up work will be sanding with rolls and flappers.

This is an example of the type of heads that can benefit from some porting work notice the thick valve guides and how the take up a large portion of the port. Much of this can be removed and still provide support for the valve at high rpm levels. These are after market heads and do not have the casting flaws of many OEM castings. You can still see there is room for improvement in these heads.

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More to follow…