Valve seats

Make

Alfa Romeo

Model

145/146 Factory Service Manual

Year

1994–1999

Section

Engine › Valve seats

Technical data and maintenanceValve seats

Valve seats

			Unit: mm
External diameter of valve seats "a"	Intake	1370	1598	1747
	Exhaust	31.635 ÷ 31.650	35.135 ÷ 35.150	27.142 ÷ 27.157	29.142 ÷ 29.157
Contact taper with valves "α"	90° ± 10'
Interference between valve seats and respective seats	Intake	0.124 ÷ 0.131	0.091 ÷ 0.131	0.100 ÷ 0.136	0.100 ÷ 0.136
Heating temperature of cylinders' head for valve seats fitting	80°C

Valves

			Unit: mm
Diameter of valve stems "a"	Intake	6.975 ÷ 6.990	1370	1598	1747
Diameter of valve heads "b"	Intake	29.9 ÷ 30.2	33.4 ÷ 33.7	Exhaust	25.9 ÷ 26.2	27.9 ÷ 28.2
Radial clearance between valve stems and valve guides	Intake	0.032 ÷ 0.065	Exhaust	0.047 ÷ 0.080

Valve springs

			Unit: mm
External spring	Internal spring
Free length "L1"	46 mm	39 mm
Length with closed valves "L2"	34 mm	29.5 mm
Load corresponding to "L2"	271 ÷ 294 N (27.6 ÷ 30 kg)	96 ÷ 106 N (9.8 ÷ 10.8 kg)
Length with open valves "L3"	24.5 mm	20 mm
Load corresponding to "L3"	485 ÷ 524 N (49.4 ÷ 53.4 kg)	201 ÷ 221 N (20.5 ÷ 22.5 kg)

Hydraulic tappets

			Unit: mm
External diameter of hydraulic tappets "a"	32.959 ÷ 32.975
Radial clearance between hydraulic tappets and corresponding seats	0.025 ÷ 0.066

Camshaft

			Unit: mm
Diameter of camshafts pins "a"	26.000 ÷ 26.015	1370	1598	1747
Diameter of phase transformer pin "b"	49.985 ÷ 50.000
Nominal cam lift	Intake	8.3	9.0 (*)	9.5
Exhaust	7.5	9.5
Clearance between camshafts' pins and corresponding seats	0.03 ÷ 0.07
Camshafts' end play	0.10 ÷ 0.23

(*) : For 98's models with M1.5.5. injection

02 Maintenance