When you’re balls deep in Nissans and your 13B Renesis runs a bearing, what do you do? For James Pera, his answer was to fish out one of the handful of RB25DETs that he had hoarded away in the shed and set about rehoming it into his RX-8’s now-empty engine bay. James tells us that the build didn’t take long at all: seven weeks, including rebuilding the motor before it went in, an effort helped by good mate Craig Dettling of Dett Spec’d.
“[The RB25DET was a] bit of a tight squeeze in the bay but does fit in there nicely,” says James. “We pushed the firewall back a little bit to get the motor and box set far enough back to line up the shifter in the factory hole too.”
Factory RB engine mounts were used to sit the motor in, and Craig modified the subframe with steel plate to create a platform for the mount to attach to, a design that James referred to as being easy and simple. It’s worth noting, however, that this is a track-dedicated car and was not required to meet the Low Volume Vehicle Technical Association (LVVTA) standards that a street-legal car would.
James tells us that the steering rack was switched out for a FC RX-7 unit and mounted low for better clearance, while the RB’s front sump was modified into a rear sump to allow it to sit over the subframe.
The package is backed by an RB20DET that gets easily swallowed by the rather hefty gearbox tunnel, although he says that it just destroys the smaller box and needs to be upgraded to an RB25 big box. The factory torque bar has been modified to keep the diff aligned.
“The conversion doesn’t seem to have affected the balance much, and with the built motor it has plenty of power. I’d give it a solid eight out of 10 in terms of worthwhileness,” James says.
RB25DET (S2) ORIGIN CHASSIS: Nissan Skyline R33 CAPACITY: 2498cc CONFIGURATION: Straight-six turbo BORE/STROKE: 86x71.7mm COMPRESSION: 9.0:1 FACTORY POWER: 186kW / 319Nm WEIGHT: 220kg (full) NOTES: Ceramic compressor wheel