Cylinder head design and specification (Mercedes-Benz E-Class W123)

The cylinder head is made of aluminum alloy, the valve seats and guides are inserted.

Characteristic	Meaning
Cylinder head height, mm
M 115
nominal	84,8—85,0
minimal	83,8
M 102
nominal	98,5—98,4
minimal	97,8
M 123
nominal	84,8—85,0
minimal	84,0
M 110
nominal	93,9—94,0
minimal	93,1
Warpage of the mating plane of the head with the cylinder block in the longitudinal/transverse directions, no more than, mm
M 102	0,10
M 115	0,08
M 110	0,08
M 123	0,08

Model	Cylinder diameter x piston stroke, mm	Working volume, cm³	Nominal power "net", kW (hp) / at crankshaft speed, rpm	Maximum torque, Nm (kgf.m) / at crankshaft speed, rpm	Compression ratio
M 115.938	87x83,6	1997	70 (94)/4800	158 (16,1)/3000	9
M 102.920	89x80,25	1997	74 (100)/5500	160 (16,3)/3000	8
M 102.939	89x80,25	1997	80 (109)/5100	172 (17,5)/3500	9
M 102.980*	95,5x80,25	2299	100 (136)/5100	205 (20,9)/3500	9
M 102.982*	95,5x80,25	2299	92 (125)/5000	194 (19,8)/3500	8
M 115.954	93,75x83,6	2307	80 (109)/4800	185 (18,9)/3000	8
M 123.920	86x72,45	2525	74 (100)/5200	183 (18,7)/3000	8,4
M 123.921	86x72,45	2525	103 (140)/5500	196 (20,0)/3500	9,4
M 110.923	86x78,8	2746	115 (156)/5500	226 (23,0)/4000	9
M 110.984	86x78,8	2746	125 (170)/5500	224 (22,8)/4500	8
M 110.988	86x78,8	2746	136 (185)/6000	240 (24,5)/4500	9

* Engines of models M 102.980 and M 102.982 have the same factory index (M 102.E23) and differ in the compression ratio and the type of fuel used.

Characteristic	Meaning
Engine valve diameter, mm
M 102.985
inlet	41,0
graduation	37,0
Roughness of the mating plane of the head with the cylinder block, µm
M 102	0,005—0,020
M 115	0,012—0,020
M 110	0,012—0,020
M 123	0,012—0,020
Length of cylinder head mounting bolts, mm
M 102
nominal	119,0
maximum	122,0
M 115
nominal	119,0
maximum	122,0
M 110
nominal	160,0
maximum	162,7
M 123
nominal	160,0
maximum	162,7

Valve seats are insertable.

When using unleaded petrol, it is necessary to install stronger valve seats.

Size, mm	Engine model
Size, mm	M 115.938	M 102.920, M 102.939	M 102.980, M 102.982	M 115.954
Valve seat diameter
nominal	48,500—48,516	46,000—46,016	46,000—46,016	48,500—48,516
repair size (no more than)	49,000	47,000		49,000
Outside diameter of saddles
nominal	48,590—48,600	46,090—46,100		48,590—48,600
repair size (no more than)	49,80	47,30		49,0800
Inner diameter of saddles
	—	37,0		—
Saddle height
	10,29—10,40	7,980—8,000		10,89—11,00
Preload when pressing in intake and exhaust valve seats
	0,08—0,10	0,074—0,10		0,08—0,10
Size, mm	M 123.920, M 123.921	M 110.923	M 110.984, M 110.988
Valve seat diameter
nominal	42,700—42,716	47,000—47,016	47,000—47,016
repair size (no more than)	43,700	48,018
Outside diameter of saddles
nominal	42,790—42,800	47,090—47,100
repair size (no more than)	44,0	48,30
Inner diameter of saddles
	—	—	—
Saddle height
	10,89—11,00	8,51—8,6
Preload when pressing in intake and exhaust valve seats
	0,08—0,10

The valve guide bushings are insertable and pressed into the cylinder head.

Parameter, mm	Intake valve guide bushings
	nominal size	1st repair size	2nd repair size
Label color	Grey-green	Red	White
	Grey
	Grey-brown
O.D	14,03—14,05	14,21—14,23	14,41—14,43
Inner diameter	9,00—9,015
Guide bushing hole diameter	14,02	14,20—14,22	14,40—14,42
Length	55,0
Wear limit	9,025
Parameter, mm	Exhaust valve guide bushings
	nominal size	1st repair size	2nd repair size
Label color	Grey-green	Red	White
	Grey
	Grey-brown
O.D	15,03—15,05	15,21—15,23	15,41—15,43
Inner diameter	11,000—11,018
Guide bushing hole diameter	15,02	15,20—15,22	15,40—15,42
Length	45,0
Wear limit	11,030