STROKING THE RB — PART TWO

BUILDING A 3400CC RB RACE ENGINE

ast issue we began following the extensive process of building an RB34 for Darren Kelly’s Nissan R35 GT-R ahead of the 2018 D1NZ season. The engine is based on an RB30E block with a Pure Performance 3400cc stroker kit and an extensively modified RB26 head.

Last issue, we covered the first stages of building the block up, and, in this issue, we’ll see the long block completed.

A stroked RB was always the goal for the R35, but time constraints forced the use of an already-built RB30 for its debut season. Having been tuned to take only 450 to 500kW, the RB30 was pushed well beyond its scope with the 550kW it produced, and it finally gave up in spectacular fashion at Mad Mike’s Summer Bash earlier this year. While the exact cause of the failure is unknown — the motor was an utter mess — the fact that the rear piston lobe sheared off is a good indication that the crank let go.

This led Thomas from Pure Performance — in Victoria, Australia — to offer the team a 3.4-litre stroker kit, 400cc bigger than those from the factory and 200cc bigger than anything Darren had previously considered. The added capacity will make a big difference, as the RB30 would run out of puff at 7500rpm, but this engine will not only have more power down low but also more legs upstairs. “We will now have the opportunity to turn the wick up to 745-plus kilowatts and match the overseas guys when needed, but, for back home, we’re not aiming to run more power, just a less stressed and more reliable engine at around the 550kW mark,” Darren explains.

DITCHING THE SHIMS

Since our last visit, the RB26 head had been assembled, using the Kelford Cams–supplied valve-train components. The number-one priority with this motor has been reliability, which meant going to a shimless bucket-style lifter — which is the small stainless cup that sits between the valve stem and the cam lobe. As the lifter transfers the cam lobe movement to the valve, it’s vital to proper valve function that the amount of lift is correct, which is where a shim would come into play. But, as the lobe has a sweeping motion on the face of the bucket or shim, at high rpm, the shims have been known to shift or spit out, and cause all types of carnage. Going to a one-piece bucket lifter not only eliminates this risk but also saves a ton of weight (upwards of 50 per cent), which helps your engine rev faster. But, as there is no longer a shim to correct the travel length, Rich modified the Ferrea valve-stem lengths to ensure that all the valves opened an equal length. You can also purchase buckets of different thicknesses to achieve this, but, as these were custom built in the UK, the boys did not have that luxury.

By the time we arrived, Rich had completed the painstaking task of installing the Kelford Cams KVS beehive valve springs and titanium retainers. A small titanium circlip holds the retainer in place. When tipping the valve, it’s important to ensure that the bucket remains only in contact with the stem and not the retainer; in this case, there was only one thou of clearance.

The block arrived fresh from the paint shop and had all-new frost plugs installed and the unwanted water and oil passages tapped, with threaded block-offs screwed in place. It was surprising just how many were on the block. The PPM crank, which was fresh from balancing and had been converted to an RB26 pulley bolt, was then bolted in place using the R.I.P.S billet main caps and ACL race bearings. The reason for running these billet main caps, which are tied to the block with a steel girdle plate, is to ensure the crank doesn’t move under extreme loads, the kind of loads you get north of 597kW. The main bolts are cranked to 74.5Nm.