RB25, RB26 and RB30 rebuild kits: what a proper package contains

Most RB rebuilds start the same way. The boost goes up on a standard bottom end, something lets go on a hot lap or a third gear pull, and by that night you are pricing pistons. The RB20, RB25, RB26 and RB30 all use a strong iron block. The factory pistons, rod bolts and head bolts are the parts that run out of talent first.

This guide covers what actually belongs in an RB rebuild kit, what our packages contain, and how to choose between them. One thing up front: we sell the parts and the packages, not complete or crate engines. If you searched for an RB26 engine for sale, skip to the last section and we will explain the honest route.

The short answer

• A refresh kit is bearings, gaskets, seals and a timing belt. Standard pistons and rods stay in. That is enough for a tidy stock power car that needs sealing up, and nothing more.
• A forged package is pistons, rods, head studs, main studs, race bearings and a metal head gasket. Our RB packages are built at this level.
• Head work goes on top of that: valve stem seals, springs, retainers, cams and adjustable gears. Do it while the head is off the car.
• Order the studs and bearings with the pistons. Splitting a rebuild across three pay cycles is the single most common reason an engine sits on a stand for a year.

What is in a rebuild package

Our Engine Rebuild Packages hub lists the standard contents: forged pistons, forged rods, a Cometic MLS or Tomei head gasket, an ARP or Mazworx head stud kit, an ARP or Mazworx main stud kit where the engine uses one, and ACL Race Series main and rod bearings. Each package is priced under the total of buying the same parts one at a time.

The RB range is split by engine and then by gasket thickness, and the product title tells you exactly what you are getting.

RB25 packages cover the RB25DET and the RB25DET Neo, with the Neo listed separately so you do not order the wrong one. The RB25 package with CP pistons, Manley rods and a 1.5mm Tomei gasket is the high boost option. The same engine is also offered with a 1.2mm Tomei gasket, and there is a CP piston, Eagle rod and 1.3mm Cometic version if you want the MLS gasket.

RB26 packages run the same three combinations for the GT-R engine: CP pistons with Manley rods and a 1.5mm or 1.2mm Tomei gasket, or CP pistons with Eagle rods and a 1.3mm Cometic.

RB30 packages are the ones where compression is stated in the title, because the RB30 bottom end gets built two very different ways. You can have CP pistons and Manley rods at 8.2:1 with a 1.3mm Cometic gasket, or the same parts at 9.0:1, and each compression is offered with a 1.0mm or 1.3mm gasket.

Choosing pistons, rods and compression

Every RB package we build runs CP pistons. They are a forged 2618 style piston with the ring pack and pin setup that a boosted RB wants, and they are what we sell most of, so stock is usually on the shelf rather than on a boat.

The rod choice is the one people agonise over. Manley and Eagle rods both go in these packages, and both are a serious step up from a factory RB rod with a factory bolt. Manley H beam rods are the ones we point drag and high rpm builds at. Eagle rods go in plenty of fast street cars and are the value option in the range. Neither will be the weak link at the power most NZ RBs actually make. What kills bottom ends is nearly always tune, oil supply or a rod bolt that was reused, which we went through in our guide on what kills JZ bottom ends. An RB is a different engine with the same lessons.

Compression and gasket thickness work as a pair. A thicker head gasket lowers static compression a touch and opens up the clearance between piston and head, which helps a big single turbo car on pump fuel. A thinner gasket keeps compression and throttle response, which suits a smaller turbo or a car on better fuel. The RB30 listings make the trade obvious: 8.2:1 for boost, 9.0:1 for response. If you are unsure, tell us the turbo and the fuel and we will point at one.

For an RB30 with an RB25 or RB26 head, we list CP hybrid pistons in both 8.2:1 and 9.0:1 in the RB30 parts collection. That combination is still one of the more popular big capacity builds in New Zealand.

Head studs, gaskets, bearings and the small stuff

Head studs are the part that stops an RB rebuild becoming an RB rebuild twice. ARP 202-4301 is the twin cam kit that covers RB20, RB20DET, RB25, RB25DET and RB30, with 202-4309 the ARP2000 version of the same kit. The RB26 uses the ARP2000 kit 202-4207. Main studs are ARP 202-5403 across the RB family. You can see the whole range in ARP head studs if you are building outside a package.

Bearings are ACL Race Series. The RB25 and RB26 share the 6B2960H rod set, the RB20, RB25 and RB30 share the 7M2394H main set, and the RB20 and RB30 have their own rod bearing part numbers, so check which engine you are actually holding before you order. Everything sits in ACL Race Series bearings.

Head gaskets come both ways. Tomei metal gaskets are listed for the RB25DET in 1.5mm and 1.2mm at 87mm bore. Cometic MLS gaskets cover RB20 at 1.3mm and RB30 at 1.0mm and 1.3mm, plus the RB25 1.3mm. Pick the bore size to match your overbore, not the stock figure.

While the front of the engine is apart, the Gates Racing T1040R timing belt fits RB20, RB25 and RB26. An ATI Super Damper is listed for both the R32 RB26 and the R33 and R34 RB26. NGK iridium plugs are split by engine, with the BKR6EIX set covering RB25DET and the BCPR6EIX set covering RB20DET and RB26DETT. Supertech valve stem seal kits cover the RB20, RB25 and RB26 head, and Tomei cam cap studs are there for RB26 heads that see serious rpm.

Cams are a separate decision. The RB25 Neo range is worth a look because Kelford design those cams around the standard variable intake cam, so you keep low rpm torque. Our Kelford cam selection guide walks through the choice properly.

Build it your way

If a package does not match what you are doing, use the Engine Builder. You pick the engine, then work through pistons, rods, bearings, gaskets and studs, and the configurator keeps the combination straight. Builders doing something unusual, like a low compression RB25 for a big turbo or a solid lifter RB26, tend to end up here rather than in a package.

The full parts catalogues per engine are RB25, RB26, RB30 and RB20. Head studs, bearings, gaskets, plugs, belts and dampers are all listed under the engine they suit.

Where NZ Performance fits

We have been selling performance parts out of Palmerston North since 2003, and we race what we sell. RB rebuild parts are held in New Zealand where we can, so a set of ARP studs or ACL bearings usually ships the same or next working day rather than waiting on an overseas order.

Worth saying again: we do not sell complete engines. Searches like "rb26 engine for sale nz" come up every week, and the honest answer is that you are better off rebuilding your block or a used import block to a spec you chose. We wrote that comparison up properly in rebuild versus import. If you are pushing the boost hard afterwards, read head studs, gaskets and pistons for big boost before you order.

FAQ

What is in an RB25 rebuild kit?

Our RB packages come with forged pistons, forged rods, a Cometic MLS or Tomei head gasket, ARP or Mazworx head studs, main studs where the engine takes them, and ACL Race Series main and rod bearings. The title on each package states the piston brand, rod brand and gasket thickness. Extras like a timing belt or valve stem seals sit in the engine collection.

Do I need ARP head studs on an RB25?

If you are lifting boost past standard on an RB25DET, head studs are the part we would not skip. The twin cam kit ARP 202-4301 covers RB20, RB25 and RB30, and 202-4309 is the ARP2000 version. Every RB rebuild package already includes an ARP or Mazworx head stud kit, so you are covered if you buy a package.

Should I run a 1.2mm or 1.5mm head gasket?

A thicker gasket drops static compression slightly and opens up clearance, which suits a high boost build on pump fuel. A thinner gasket keeps compression and response for a smaller turbo. Our RB25 and RB26 packages come with 1.2mm and 1.5mm Tomei gaskets and a 1.3mm Cometic, so match it to the piston and the tune.

Can I buy a complete RB26 engine from NZ Performance?

No. We sell rebuild parts, rebuild packages and the Engine Builder, not complete or crate engines. Most people searching for an RB26 for sale end up rebuilding their own block or a used import block, which costs less and leaves you knowing exactly what is inside it.

Is an RB30 bottom end worth it over an RB25?

An RB30 gives you more capacity for the same boost, which is why the RB30 block with an RB25 or RB26 head is still a common NZ build. We list CP hybrid pistons for it and RB30 packages in 8.2:1 and 9.0:1. Budget for the extra machining, because the parts are only part of the job.