Reinforced inlet valves MINI Cooper S JCW N18B16A N18B16C

MINI engines covered

The N18B16A and N18B16C took over from the N14 under the bonnet of the MINI Cooper S and John Cooper Works: a 1.6 turbo four-cylinder with 16 valves, extensively reworked. From 2007 to 2016 it powers the R55 Clubman, R56, R57 Convertible, R58 Coupé, R59 Roadster, R60 Countryman and R61 Paceman, with 122 to 218 hp depending on version.

Each engine has 8 inlet valves, two per cylinder. The original part 11 34 7 585 901 has a 29.7 mm head and a 4.97 mm stem, held by 5 mm collets. Modified software, a harder-pushed turbo or a livelier cam profile put these valves through temperatures and impacts well beyond standard.

SUPERTECH reinforced inlet valves

On every cycle, the N18 inlet valve tips open to let the pressurised air in, slaps against the seat as it closes and goes back to sliding in its guide. It takes 400 to 550 °C, where the chrome-silicon steel fitted to factory heads falls away: 500 MPa at 500 °C, but barely 250 MPa at 600 °C, 50 % less strength. More boost and higher revs make this effort worse still.

SUPERTECH shapes it from stainless steel and treats it with black nitriding: this hard surface keeps the stem from catching and extends the life of the valve and guide pair. The top of the head is dished, the stem ends in a 5.8 mm tip and the single groove takes the KPR-5.0/7S collets.

Inlet valve technical specification

MCIVN-1301S-8: set of 8 valves at the maker's standard size, dished head, 5.8 mm stem tip.

Fitting details

With this single-groove valve, SUPERTECH pairs its KPR-5.0/7S collets, to be fitted new.

Kept at standard diameter, the head rests on the original inlet seats: lapping or a light recut is enough during the rebuild.

Technical guide

The brand offered

Based in California, SUPERTECH has produced racing cylinder head parts for more than thirty years. Before any shipment, every valve undergoes an ultrasonic examination, an X-ray and a laser check of its dimensions, then joins engines entered on circuit, in rallies and in drag racing.

How to choose

One part number for the N18: at factory diameter, no seat work is needed; its appeal is the stainless steel and the black surface treatment.

When reinforced valves become necessary

• Sharper camshafts, stiffer valve springs
• Boost and revs reworked by software
• Hybrid or larger turbo grafted onto the N18
• Head rebuilt for track, rallying or hillclimbs
• Worn MINI valves or seats recut repeatedly

Compatible vehicles

OEM reference (inlet valve): 11 34 7 585 901

Don't forget the exhaust valves

While the cylinder head is off, replace the 8 exhaust valves too: a reinforced set of the same quality for these MINI N18 is on this page: