STROKING THE RB — PART TWO

BUILD­ING A 3400CC RB RACE EN­GINE

NZ Performance Car - - Contents - WORDS AND PHO­TOS: MAR­CUS GIB­SON

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.

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