Reinforced exhaust valves BMW M42B18 M44B19

BMW engines covered

The M42B18 is a 1.8 litre inline four-cylinder with twin overhead camshafts and 16 valves (84 mm bore, 81 mm stroke), built from 1989 to 1996; the 1.9 litre M44B19 (85 x 83.5 mm) succeeded it from 1996 to 2000. They power the E36 3 Series, including the 318i, 318is and 318ti Compact, as well as the Z3 1.9. Since September 1992, the M42B18 cylinder head has taken valves with a 6 mm stem, which the M44B19 retains.

Each of these four-cylinder engines has 8 bi-metal exhaust valves, BMW part number 11 34 1 739 823, the same part as on the M50 VANOS, M52 and M54 six-cylinder engines: 30.5 mm head, 6.0 mm stem, 105.7 mm length and 3 grooves that take the 11 34 1 461 405 collets. Intended for standard use, they cope poorly with an engine that revs higher, works under more load or runs hotter on the exhaust side.

SUPERTECH and FERREA reinforced exhaust valves

On the exhaust side, the valve lets the burnt gases out to the manifold, and it is the part that runs hottest: its head reaches 760 to 870 °C on a naturally aspirated engine such as the M42 or M44, and exceeds 1,000 °C with a turbocharger or supercharger. About 75 % of this heat flows out through the seat and 20 % through the guide. The original chromium-manganese-nickel steel head still withstands 550 MPa at 600 °C, but drops to 300 MPa at 800 °C. With more revs, more load or boost pressure, the valve runs hotter, fatigues, can distort and then no longer seal properly.

To withstand these temperatures, SUPERTECH uses a high temperature steel and, above all, Inconel, a nickel-based superalloy: 860 MPa at 730 °C and still 554 MPa at around 815 °C, giving about 85 % more strength than the original steel at around 800 °C. For its Competition Plus range, FERREA states 20 % more hot strength and a seat that lasts 25 % longer. This set of 8 comes in three finishes: SUPERTECH black nitride stainless steel, surface-hardened and smoother, which rubs and wears less in the guide; SUPERTECH Inconel, the one to choose for a turbocharged or supercharged engine; the FERREA hard chrome stem.

The +1 mm oversize enlarges only the head, from 30.5 to 31.5 mm. The cylinder clears its burnt gases faster, freeing room for the fresh charge and helping to gain power. It requires a cylinder head whose exhaust seats are machined to this size.

Exhaust valve technical specifications

Valve fitting

Each groove type has its own collets: KPR-VW6-T on 3-groove valves, KPR-6S-7 on single-groove valves. A single-groove valve is never fitted with the original BMW collets.

With a +1 mm oversize head, the exhaust seats in the cylinder head must be recut to the new size: a job for the machine shop during the rebuild.

Technical guide

Our brands

	SUPERTECH, based in Silicon Valley, has been designing valvetrain parts for motorsport for more than 30 years: valves, springs, titanium retainers and guides. Each valve, in stainless steel, titanium or Inconel, is drawn up for a specific engine and then proven by engine builders on circuits, rallies and drag strips.
	FERREA Racing Components, founded in 1978 by Horacio Ferrea and Daniel Urrutia, makes its valves in its own workshops in Florida and Argentina, in stainless steel, nickel-based superalloys or titanium. NASCAR and drag racing engine builders are among its customers around the world.

How to choose

The valve stem carries one or three grooves, into which the collets fitted under the retainer lock. The number of grooves changes how the valve is held, and therefore what it can withstand.

When reinforced valves become necessary

• Higher lift camshafts or stiffer valve springs
• Rev limiter raised
• Turbocharger or supercharger fitted (Inconel version recommended)
• Cylinder head rebuilt for track, drift or rally
• Original valves damaged, worn or already at repair size

Vehicle compatibility

OEM part number (exhaust valve): 11 34 1 739 823

Don't forget the inlet valves

When the cylinder head is rebuilt, the inlet valves are replaced at the same time as the exhaust valves. The reinforced version for these engines: