The Castrol Syntec Top Shop Challenge has become a classic game of teams and magazine staff scrambling to see who is building what type of engine and how much power they plan to make. We're not the type to beat around the bush, so we'll come out and let them, as well as our readers, know we're building our RB26DETT engine to eclipse the 1,000-plus horsepower marker without breaking a sweat. Sure, it's been done before. The RB26DETT motors have been known to hit the 600hp marker with simple bolt-on goodies but for competition purposes and looking to score big in the "Power Under The Curve" category, SP Engineering and Turbo magazine devised a plan to build a solid motor that can deliver some reputable numbers while withstanding more than a few simple passes on the engine dyno.
As we begin part one of our engine build, SP Engineering will be focusing on the RB26 cylinder head port and prepping process. The common misconception is that porting requires the ports to be as big and round as possible. Yes, producing good airflow through the cylinder head and out of the exhaust port is essential in producing big power. However, over-porting will cause an irregularity in velocity and air speed, causing the car to become sluggish at bottom to midrange power, which makes the car nearly impossible to drive on the street. Hirofumi Kondo, chief mechanic of SP Engineering takes us through the steps in building the SP Engineering/Turbo magazine RB26DETT, destined to dominate the Castrol Syntec Top Shop Challenge. In our next issue, we'll cover the bottom end buildup and what it takes to deliver 1,000-plus horsepower.
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While both RB26DETT cylinder...
While both RB26DETT cylinder heads look similar, these two sport very different port and prep characteristics when analyzed up close. For show-and-tell purposes we'll call the competitor's ported cylinder head No. 1, while the other will be known as the SP Engineering head. Never judge a book by its cover.
SP Engineering performed much...
SP Engineering performed much of the porting on the cylinder head but also commissioned Tom Fujita of Port Flow Design to touch-up any rough edges while performing a three-angle valve job and resurfacing of the head.
Notice on the factory head,...
Notice on the factory head, looking through the valve seats into the exhaust ports, the material around the valve seat juncture, otherwise known as "humps," can cause unwanted turbulence when looking to extract maximum horsepower.
Although there are many pros...
Although there are many pros and cons with removing the junctures, such as weakening of the seats and valves, this modification has been tried-and-true on many RB26 engines without any issues.
During the porting process,...
During the porting process, Port Flow tapered and cut back the valve guide sections by shaving it down to match the ceiling in order to offer a smoother transition of air entering and exiting the ports. A new set of HKS valve stem seals were installed prior to reinserting the factory valves.
Notice on the factory head,...
Notice on the factory head, looking through the valve seats into the exhaust ports, the material around the valve seat juncture, otherwise known as "humps," can cause unwanted turbulence when looking to extract maximum horsepower.
A good cylinder head porter...
A good cylinder head porter will shape the port to get the maximum flow with a minimal amount of enlargement while increasing flow velocity. Becoming overzealous in the ports and grinding away at the bowls will affect the vehicle's performance. Notice the difference in ports with the SP Engineering head compared to the previous image. Now which do you think flows more efficiently?
Hiro points toward the factory...
Hiro points toward the factory quench pad on the SP Engineering cylinder head. For this build, we plan to keep the quench area in factory specs. The reason behind the SP Engineering theory is plain and simple. The unmodified combustion chamber promotes a smaller area quench pad that keeps energy tight, compact, and ready to explode. The burn efficiency maintains optimal use of the flame and spark energy creating a full burn.