Supertech 81/81.5/82mm Piston Rings for B16/B17/B18 Engines

Supertech Piston Rings - Honda/Acura B16, B17 & B18 (81/81.5/82mm)

If you're building or rebuilding a B-series, the piston rings are one of the parts you don't reuse and don't cut corners on, they're what seal combustion pressure in the cylinder and keep oil out of it. These Supertech rings are built for the B16, B17, and B18, available in three bore sizes to match a standard or bored block. They're sold individually (one set per cylinder), so a full engine needs four. Note up front: these do not fit the B20, which has a larger bore.

What Piston Rings Actually Do

Worth understanding, because they do more than people realize and it's why they matter so much in a build.

Each piston has a set of rings that ride in grooves around it, and they do two critical jobs. The compression rings (the top two) seal the gap between the piston and the cylinder wall, so the pressure from combustion stays above the piston and pushes it down instead of blowing past it. That seal is where your compression and your power come from, worn rings let pressure escape (blow-by), which costs you power, fouls the oil, and shows up as low compression on a leak-down test.

The bottom ring is the oil control ring, and its job is the opposite: it scrapes oil off the cylinder wall on the way down so it doesn't get burned in the combustion chamber. Worn oil rings are why an engine burns oil and blows blue smoke, the oil's getting past them into the cylinder.

So the rings are doing two things at once: holding combustion pressure in, and keeping oil out. In a fresh build, the rings are what make the difference between an engine that seals properly and makes its power, and one that's down on compression and burning oil from the start. That's why you always fit fresh rings in a rebuild, and why ring quality matters.

Pick Your Bore Size

These come in three sizes to match your block, so measure before you order.

81.0mm is the standard bore, for a block that's at factory spec or being rebuilt without boring.

81.5mm is 0.5mm over, for a block that's been bored 0.5mm oversize (common when a cylinder needs cleaning up).

82.0mm is 1.0mm over, for a block bored 1.0mm oversize.

The ring size has to match your pistons and your actual bore exactly, over-boring is how a machine shop cleans up a worn or damaged cylinder, and the rings (and pistons) step up to match. If your block's been bored, you order the ring size for the final bore, not the original. If you're not sure of your bore, measure it or check with your machine shop before ordering.

Sold Individually — A Full Engine Needs Four

Important so you order the right quantity.

These are sold as a single-cylinder set (one set of rings for one piston). A B-series is a four-cylinder, so a full engine build or rebuild needs four, one set per cylinder. Order four if you're doing the whole engine; order one if you're replacing the rings on a single cylinder for some reason. It's an easy thing to under-order, so count your cylinders before checkout.

Does Not Fit The B20

A hard fitment limit worth being clear on.

These fit the B16, B17, and B18, but not the B20. The B20 has a larger 84mm standard bore, so none of these ring sizes (81/81.5/82mm) will fit it, the B20 needs its own 84mm-and-up rings. If you're building a B20 or a B20-based hybrid (like a B20/VTEC), these aren't your rings. For the B16, B17, and B18, match the bore size above and you're set.

Ring Dimensions

All three sizes use the same ring profile, 1 x 3.10mm top, 1.2 x 3.40mm second, 2.8 x 3.10mm oil, with the diameter matched to the bore.

Fitment

Honda/Acura B16, B17, and B18 engines (does not fit B20)

Available in 81.0mm (standard), 81.5mm (0.5mm over), and 82.0mm (1.0mm over) bore. Sold individually, four required for a full engine.

If you're building or rebuilding a B16, B17, or B18, these are the rings that seal the combustion pressure in and the oil out, the foundation of an engine that makes its power and doesn't smoke. Measure your bore to pick the right size, order four for a full engine, and if you're on a B20, these aren't the ones. Fit fresh rings and build it to seal properly from the first start.