Reinforced exhaust valves BMW M42B18 7 mm stem

BMW engines covered

The M42B18 is a BMW 1.8 litre four-cylinder with twin overhead camshafts, 16 valves and hydraulic tappets, fitted to the 318i and 318is. Until September 1992, its cylinder head takes valves with a 7 mm stem.

This first version has 8 exhaust valves, BMW part number 11 34 1 722 891, held by 3-groove collets 11 34 1 307 136. The engine likes to rev, and its burnt gases heat these valves hard at every acceleration.

CATCAMS reinforced exhaust valves

The metal of an exhaust valve head reaches 760 to 870 °C on a naturally aspirated engine. Around 75 % of that heat leaves through the seat and 20 % through the guide. An EV8 family steel keeps 550 MPa at 600 °C but offers only 300 at 800 °C: beyond that, the head fatigues, distorts and seals less well.

For this 7 mm stem cylinder head, CATCAMS offers the 9213006M, sold here as a set of 8: 29.5 mm head, 7 mm stem, 109.4 mm length.

Exhaust valve technical specifications

9213006M: the only exhaust valve in the range for the 7 mm stem M42B18.

Valve fitting

When refitting, check that each collet sits properly in the stem groove before releasing the spring.

The exhaust seats are reground to seat on the new valves; take the opportunity to check the guide clearance.

Fit all 8 valves from the same set and replace the exhaust valve stem seals during the same job.

Technical guide

Our brand

CATCAMS designs and manufactures camshafts and valvetrain parts in Europe for engine tuning. For the 7 mm stem M42B18, the brand offers the 9213006M, sold here as a set of 8.

How to choose

Only one version exists for this engine:

When reinforced valves become necessary

• Sharper camshafts or stiffer springs
• Raised rev limit
• Track, autotest or rally use
• Rebuilt cylinder head with pitted or distorted exhaust valves

Vehicle compatibility

OEM part number (exhaust valve): 11 34 1 722 891

Don't forget the inlet valves

With the M42B18 cylinder head on the bench, it is the right time to replace the inlet valves and the valve stem seals as well.