Bearings are the cheapest part in a bottom end and the one that decides whether the rest of it survives. A set of shells costs less than a tank of fuel, and yet we still see engines come apart with the factory bearings back in because the crank looked fine. The ACL range covers most of what gets built here, and choosing from it comes down to your crank rather than your power target.
The short answer
- ACL Race Series is the default for any boosted rebuild. Fit them whenever the bottom end is open.
- STD in the part number means standard size, for a crank that has not been ground. A ground crank needs the matching undersize set.
- Check whether your engine needs a separate thrust washer set or gets thrust as part of the main set.
- Never fit bearings without measuring the clearance. The set is right or wrong at the crank, not on the shelf.
What Race Series bearings actually are
ACL builds the Race Series around a tri metal construction aimed at motorsport loads rather than at a quiet factory engine. That is the short version of why they end up in almost every performance rebuild that leaves a workshop here.
ACL is Australian, based in Launceston, Tasmania, and has been making bearings since 1949. The practical upside for us is availability. Getting a set here does not mean waiting on a container from the other side of the world, which matters when an engine is in pieces on a stand.
The Race Series range covers the engines NZ builders actually work on, and the wider ACL catalogue picks up the oil pumps and odds and ends that go with them.
Reading the part number
An ACL number like 4B1185H STD looks like noise until you know what to ignore. The letter and digit prefix tells you the family, so a set starting with 4B or 6B is a rod bearing set and one starting with 5M or 7M is a main set. The count in there tracks the number of shells, which is why a four cylinder rod set and a six cylinder rod set read differently.
STD on the end is the part that costs people money. It means standard size, so the shells suit a crank still at its original journal diameter. If your crank has been ground during the rebuild, the standard set will not give you the clearance you need and you order the matching undersize instead. Get that number from whoever measured the crank.
Picking the set for your engine
Nissan
RB builders want the RB20, RB25 and RB30 main bearing set ACL 7M2394H with the RB25 and RB26 rod set ACL 6B2960H. There is also a rod set listed for the RB30 and VG30.
The SR20 is covered end to end: the main set ACL 5M2964H, the rod set ACL 4B2960H and a separate thrust washer set ACL 1T2964. That thrust set is a line people leave off the order and then wait on.
Toyota
For a JZ bottom end, the 2JZ rod bearing set ACL 6B8100H is the one, with a thrust washer listed separately again. Older Toyota builds get the 4AGE rod set ACL 4B1780H, and there is a 3SGTE rod set in the range as well.
Mitsubishi
The 4G63 splits by generation, so read carefully. There is a 4G63 rod bearing set ACL 4B1185H, and for the later Evos a main set ACL 5M1219H with its own thrust washer for the Evo 5 to 9.
Subaru
EJ builders want the rod bearing set ACL 4B8296H and the main and end thrust set ACL 5M8309H. Note that the rod set is listed as 52mm. Subaru rods are not all the same journal size, so confirm which rods you have before you order rather than after the parcel arrives.
| If you are building | Order | Watch for |
|---|---|---|
| RB25 or RB26 | 7M2394H main plus 6B2960H rod | The RB30 and VG30 rod set is a different number |
| SR20DET | 5M2964H main, 4B2960H rod, 1T2964 thrust | The thrust washers are a separate line |
| 2JZ | 6B8100H rod set | The thrust washer is its own part number |
| 4G63 Evo 5 to 9 | 5M1219H main, 4B1185H rod, 1T1219 thrust | Earlier 4G63 variants differ, so check the year |
| EJ20 or EJ25 | 4B8296H rod, 5M8309H main and thrust | The rod set is listed as 52mm journal |
Clearance, and why measuring beats guessing
A bearing set does not have a clearance. The clearance is what you get once those shells are in your rods and caps around your crank, and it changes with wear, with a grind, and with how the rods were resized.
So measure it. Plastigauge is fine for a home build if you are honest with yourself, and a bore gauge with a micrometer is what a workshop uses. Your engine builder will pick a target clearance based on the oil you plan to run and the rpm the engine will see, which is a conversation to have before the crank goes to the grinder rather than after.
While you are in there, check the oil pump. A tired pump undoes good bearing work quickly, and the ACL oil pump range covers the usual suspects for these engines.
ACL or King
King is the other name that comes up in searches. Our King range is narrow and specific. We list a race main bearing set, a big end rod set and a thrust washer for the 3SGTE in the King range.
If you are building a 3SGTE, price that against the ACL equivalent before you decide. For everything else on this page, ACL has the coverage and there is no real argument to be had.
What to buy with them
Bearings go in as part of a bottom end job, so order the rest of it in the same hit. ARP main studs go in while the block is at the machine shop, because the mains normally get line honed with the new studs fitted. If the pistons are coming out, the forged piston range covers the same engine families, and assembly lubricant on the shells during the build is not optional.
Where NZ Performance fits
We hold ACL Race Series sets in Palmerston North and ship them out the same week, which is the difference between a build losing a weekend and losing a month. The ACL Race Series page lists what the range covers.
If the bearings are part of a full rebuild, our SR20 rebuild kit guide and the EJ20 rebuild guide show where they sit in a complete package. And if you want the blunt version of why bottom ends die, what kills JZ bottom ends is the one to read before you order anything.
FAQ
What makes ACL Race Series bearings different from standard bearings?
They use a tri metal construction built for motorsport loads rather than for a quiet factory engine. In practice they cope better with what a turbo engine puts through a rod journal, and they suit the clearances a builder wants for a hard used engine.
What does STD mean in an ACL part number?
STD is standard size, meaning the shells suit a crank still at its original journal size. If the crank has been ground undersize during the rebuild, you need the matching undersize set instead. Measure the crank, or get the number from your machinist, before you order.
Do I need a thrust washer set as well?
On some engines, yes. ACL list separate thrust washers for the SR20, the 4G63 Evo 5 to 9 and the 2JZ, while the Subaru EJ set is listed as a main and end thrust set. Check which way your engine is listed.
Are ACL bearings made in Australia?
ACL is an Australian company based in Launceston, Tasmania, and has been building bearings since 1949. That closeness helps with availability here compared to a lot of American brands, which is one reason ACL is what most NZ engine builders reach for.
ACL or King bearings, which should I buy?
For most Japanese performance engines, ACL is the practical answer because the coverage is far wider. King is worth knowing about for the 3SGTE, where we list race main and big end sets plus a thrust washer. Either way, buy the bearings and the clearance measurement together rather than assuming.
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