Project STurdteen: Prepping SR20DET Heads with Portflow Design

by Rathyna Gomer


For those of you who have been keeping up with my Project STurdteen drift car, you will see that we spent a good amount of time overhauling the suspension and making small gains with some bolt-ons. After I took her out for my first track day, I unknowingly lost the dipstick at some point and discovered a slight ticking noise in the head. After conducting a leak-down test, we discovered that two of the cylinders were down over 25%. In other words, the Turd’s heart was a bit worn down and it was time for a rebuild!

Before diving into the block, we decided to work with the amazing Tom Fujita from Portflow Design to begin working on my SR20 head. Portflow designs uses the Newen valve seat cutting machine.

The Newen is innovative as it does not use stones or cutters like the traditional valve seat cutting machine used in valve jobs. The Newen is a CNC style cutter that uses a tool bit to shape the seat and surrounding head for optimal flow. Instead of abrupt angles like old style cutters, the Newen makes a smooth radius for best flow.  

The Newen also blends the valve seat into the combustion chamber and the port, eliminating turbulence causing steps. If done correctly, a Newen valve job can make much of the flow gains that a fully ported head can make!


Before getting started, Tom measures the diameter of the valve seats. From this, Tom can program the Newen to open up the seat larger to accommodate more airflow. With a larger cross section area and having everything blended together, the valve job can greatly increase flow.

We didn't show it, but my head was pretty hammered. This required getting new bronze valve guides from Supertech to go along with my Supertech stainless intake valves and heat-resistant Inconel exhaust valves. SR20's are pretty hard on guides, so this is not unheard of for an SR that has seen a rough life.


Like we said before, Portflow Design is one of the flew places that has a Newen machine which is a much more advanced and precise way of conducting high-performance valve jobs.  The Newen machine, like a CNC machine, needs to be programmed to cut the desired valve seat contours. 

Tom programs the Newen to cut the valve seats and contours. The software is extremely impressive. There is infinite flexibility on the angle of the valve seat and angle cuts. You can see how the machine pictures the cut contour on its own screen. 
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Monday, June 19, 2017 1:12 PM
Since the valve seat has a continuous radius, wouldn't very little of the backside of the valve actually contact the seat, therefore making sealing of the cylinder and cooling of the valve more difficult?
Chris "Shaggy" Allenlink
Monday, June 19, 2017 2:50 PM
IMO It would be wise to open up the chamber like a 54C head has. When the piston is at TDC there’s little to no room at the side of the head and seems to be really hot under there.. A few engines I have pulled down always seem to detonate under there. I suspect this is why the 54C is open from the OEM.
Monday, June 19, 2017 3:54 PM
"This is because the valve spends the most time around the seat rather than at full lift, so partial lift flow is the most critical for power production."

I've been applying a small (2-3mm) radius to throttle plates for a long time to enhance throttle tip-in. It's such a huge difference that you usually have to retune the ECU to get proper idle and part-throttle performance. And this is for a 'radius' to a edge that was sharp before. There is such a huge difference in flow because of the negative pressure conditions add to the effect. Fluid mechanics is really fascinating.
Monday, June 19, 2017 4:03 PM
So what was the total cost for this process?
Mike Kojima
Mike Kojimalink
Monday, June 19, 2017 10:01 PM
The seat isn't a radius, the cuts leading up to it are.
Mike Kojima
Mike Kojimalink
Monday, June 19, 2017 10:02 PM
Shaggy, removing the quench would actually make most engines more prone to detonation but the SR and the VR seem to respond to this.
Chris "Shaggy" Allenlink
Tuesday, June 20, 2017 8:01 AM
Mike I would suspect that as I see a lot of engines do have the quench area but was odd why the 54C didn't have it tell later when I pull engines down and almost always theres damage under the quench. I wonder if its just a really tight area on the SR . Would be interesting to measure that area vs other engines to understand why it is like that with the SR..
Wednesday, June 21, 2017 3:29 PM
Now who signed off on putting all this work into an engine that has been classified as "sucking"??


Mike Kojima
Mike Kojimalink
Thursday, June 22, 2017 12:02 AM
It sucks - that's why it needs all of this work.
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