We have been getting parts to finish off the engine build on Project GD WRX. If you have been following the project you can check out what we have done on the car and our video on the engine internals. Let’s start off with the heads. Since this was a really tired beat engine with lots of miles and abuse we had to totally go through them.
We sent the heads to Port Flow Design to be CNC ported and rebuilt. The intake porting is pretty straightforward with a slight raising of the port roof and narrowing down the port splitter for more port area.
The exhaust side porting gives attention to the infamous Subaru dogleg port to try to equal out the flow between the ports.
Port Flow also cleaned up the combustion chamber and did one of their terrific Newan CNC radius valve jobs. The Newan machine cuts a perfect radius from the combustion chamber to the valve seating surface to the port wall. This valve job is good for a decent amount of power. In the case of our engine, the Newan machine can also open up the seat and the throat of the port for larger valves.
To replace the well-worn intake valves we used Supertech’s black nitrided stainless oversize valves, 37mm in diameter vs the OEM 36mm. This allows us to open up the seats for a fresh high seat for the best flow. The larger valves also flow better. The intake valves are made out of EV8 stainless steel. The intake valve back face is flatter to help flow into the cylinder, think of a nail head. The forward face of the valves is flat to help get higher compression and to have less effect on flame travel in the combustion chamber.