Boundary Billet Oil Pump Gears for B18C1/B18C5

Boundary Billet Oil Pump Gears - Honda B18 (Orbit Pump Only)

If you're building a B18 that's going to see real rpm, the oil pump gears deserve more attention than they usually get. Factory gears are sintered powdered metal at roughly 6,000 PSI of strength, and a B-series that lives at 8,000-plus rpm asks a lot more of them than a commuter ever did. These Boundary gears are billet steel approaching 110,000 PSI yield strength, cut in-house, and heat treated for operation above 9,000 RPM.

Read This First: Orbit Pump Only

Most important thing on this page. These gears fit the Orbit pump only. Honda used more than one oil pump design across B-series engines, and having a B18 does not tell you which pump is bolted to yours, especially on an engine that's been swapped, rebuilt, or assembled from parts over the last thirty years.

So before you order, pull your pump or confirm what's on it. If you're not certain, reach out and we'll help you sort it out. It's a five-minute check that saves you from buying gears that won't fit a pump you've already got apart.

Why Sintered Gears Are The Weak Link

Honda makes OEM oil pump gears by sintering, which is a cost-efficient process that produces tighter tolerances than casting. The tradeoff is strength: sintered powdered steel is actually weaker than a casting, coming in around 6,000 PSI. That's adequate for the duty cycle Honda designed for and marginal for a built B18 spinning hard on a road course or down a drag strip.

Boundary starts from solid billet steel approaching 110,000 PSI yield strength, roughly 18 times stronger, and cuts every tooth themselves. They developed the specific steel grade and heat treat alongside metallurgists, and every gear traces back to its original material spec sheet through an HT number stamped on it.

MartenWear Dual-Stage Heat Treat

These carry Boundary's MartenWear dual-stage heat treatment, rated for operation over 9,000 RPM. That matters on a B-series more than most engines, because these motors get revved. A dual-stage process gives you hard wear surfaces plus a tough core, so the gear resists wear without going brittle under the cyclic loading that high rpm creates.

Tested And Backed

Boundary flow-tests every design on their own bench to 12,000 RPM before it goes out, and they hold two US patents on their pump designs. Everything is machined in the USA, and it's covered by a lifetime warranty.

Fitment

These gears fit Honda B18 1.8L engines using the Orbit pump. Confirm your pump type before ordering.

Who Should Run These Gears

This is for the B18 builder putting an engine together properly, or anyone with a high-rpm B-series who'd rather not find out what a cracked pump gear does to a bottom end. If the pump is already off the engine, this is the moment. Confirm you're running an Orbit pump, order the right set, and build it once.

Fits: Honda B18 1.8L with the Orbit pump only. Part number: B18-OPG. Material: billet steel, approximately 110,000 PSI yield strength versus roughly 6,000 PSI for OEM sintered gears. Heat treat: MartenWear dual-stage, rated for operation over 9,000 RPM. Testing: flow-tested to 12,000 RPM. Warranty: lifetime. Made in the USA.