Project Do It All S13, Assembling the Bulletproof SR20DET Cylinder Head!

In our last edition of Project Do it All S13, were covered the build of our 2.2 liter bottom end.  Now we are going to turn our attention to the cylinder head which we completed with help from DSport, Supertech, WPC Treatmentmt, CTP Cryogenics, and Jim Wolf Technology.

One of the major reasons why the SR20 engine falls short of newer designs like the Honda K motor is that the ports do not flow very well compared to the Honda K and even the older B series engine.  This is not as much of an issue with us since our engine is turbocharged but we would like to make good power and torque with less boost for reliability.  For this reason we are addressing the flow of our engine with some porting by DSport.

The head was ported by DSport, we wanted a mild port job done to address some of the SR20’s obvious flow shortcomings but without increasing the port volume much which might make the engine have a soggy bottom end and more turbo lag.  One of the issues of the older high port SR20 heads is that the port splitter is really wide to accommodate the hydraulic lash adjuster.  DSport opened up the port to the inside and slightly narrowed the splitter to improve this area.

The exhaust port was slightly opened up as well.  The idea is to improve flow and velocity by smoothing but increasing volume as little as possible.

The port bowls were smoothed out under the valve seat and the bowl exits were opened up to the port size.  The short side radius on the intake port is very sharp and really hurts flow and this was rounded as much as possible. The short side radius of the exhaust bowl was also rounded.  These changes greatly improve port flow without increasing port volume too much.

Since the SR20 is hard on valve guides, we replaced the OEM iron valve guides with Supertech silicon bronze parts.  The bronze is easier on the valve stems and more abrasion-resistant. The sides of the combustion chamber were cut back to unshroud the valves to improve low lift flow.