Inside The AMS CNC Head Program

Written by AMS Performance

The EVO X Head

Tim and the guys in the engine shop have been working pretty diligently on an engine program for the EVO X. With the great success we have had with CNC heads on the EVO VIII and IX we knew it was a must to develop a head for the evo X. I wanted to share a bit of the process involved in the CNC porting process.

I am going to show you a series of pictures in sequential order of the CNC process. each will be labeled with a corresponding number, 1-4. Below are the descriptions of each stage of porting all the way up to the final product.

  1. As cast by OEM, this the way your stock EVO X cylinder head would look
  2. CNC ported: Note the un-machined areas in both the port and the chamber. These areas will vary from casting to casting. In some castings a port wall or roof may be left un-machined. This is due to the acceptable tolerances for castings, which allows for a greater amount of deviation in port location and shape than the CNC machining process. During CNC machining, an exact copy of the port shape and size is machined into the casting regardless of the variations in the casting.Of course, you could modify the CNC program to machine the un-machined areas. This approach would result in the CNC “look” in all the ports, on all the surfaces. The drawbacks is the “modified” port would result in a larger than desired port volume and / or a port shape that is not the same as the originally developed port.With all of the above considerations, it is our approach to cut the developed and tested port shape into a casting along with lightly hand finishing the un-machined areas in. This is not only more aesthetically pleasing, but proven to obtain the exact results our customers expect. The results are verified on our Superflow SF-600 flow bench by comparing each heads flow numbers after machining to the results of the original “master port”
  3. Hand finishing and blending; this step cleans any transition lines left during the machining process and blends in the previously mentioned un-machined areas.
  4. Finished; All surfaces polished along with a valve job and blending

Lets start with the bowl area on the head

First is the stock bowl on the EVO X. Again this is what your stock head is like.

Here is after the first stage of porting.

Here is the bowl after the next stage in porting.

And finally the finished bowl.

Now lets move to the exhaust port on the EVO X head

First is the stock exhaust port.

Step 2 on the exhaust port.

Step 3 on the exhaust port.

Finally the finished product.

Lastly we move to the intake port on the EVO X head

The Stock Port

After the initial CNC work

Some more hand finishing.

The final product, Thats a great deal bigger and smoother!

An inside look at the CNC porting program here at AMS for the EVO X.


The goal of AMS is to provide the highest quality, best performing products available.
By utilizing research and development and rigorous testing programs AMS will never compromise the quality or performance of our products.

Check out with afirmFree

On all orders over $199.99 in the lower 48.*Freight items not included*