Piston

Make

Alfa Romeo

Model

145/146 Factory Service Manual

Year

1994–1999

Section

Engine › Piston

Technical data and maintenancePiston

Piston

Unit: mm
	AR 33501	AR 33201
Diameter of pistons "a" (1)	Class A - Blue	79.960 ÷ 79.970	83.950 ÷ 83.960
	Class B - Pink	79.970 ÷ 79.980	83.960 ÷ 83.970
	Class C - Green	79.980 ÷ 79.990	83.970 ÷ 83.980
	Class D - Yellow	79.990 ÷ 80.000	83.980 ÷ 83.990
	Class E - White	80.000 ÷ 80.010	83.990 ÷ 84.000
	Oversize 0.2	80.154 ÷ 80.170	---
	Oversize 0.4	80.354 ÷ 80.370	84.346 ÷ 84.364
	Oversize 0.6	80554 ÷ 80.570	---
Height of first seal ring seat "b"	1.525 ÷ 1.545	1.525 ÷ 1.545
Height of second seal ring seat "c"	1.775 ÷ 1.795	1.510 ÷ 1.530
Height of oil scraper ring seat "d"	4.015 ÷ 4.035	3.510 ÷ 3.530
Diameter of gudgeon pin hole in pistons "e"	21.004 ÷ 21.008
Clearance between cylinder and piston (not oversized)	0.03 ÷ 0.05

(1) To be measured perpendicular to the gudgeon pin hole at a distance of 14mm from the lower edge of skirt for "Borgo" pistons and 11.5 mm from the pin axis for "Mondial" pistons.

Piston rings

Unit: mm
	AR 33501	AR 33201
Thickness of rings "a"	First ring	1.478 ÷ 1.490	1.478 ÷ 1.490
	Second ring	1.728 ÷ 1.740	1.478 ÷ 1.490
	Oil scraper ring	3.978 ÷ 3.990	3.478 ÷ 3.490
Ring gap "b" (1)	First ring	0.30 ÷ 0.45	0.3 ÷ 0.5
	Second ring	0.30 ÷ 0.45	0.3 ÷ 0.5
	Oil scraper ring	0.25 ÷ 0.40	0.25 ÷ 0.40
Axial play between piston rings and seatings	First ring	0.035 ÷ 0.067	0.035 ÷ 0.067
	Second ring	0.035 ÷ 0.067	0.020 ÷ 0.052
	Oil scraper ring	0.025 ÷ 0.057	0.020 ÷ 0.052

(1) To be measured in the checking ring nut or in the cylinder.

Gudgeon pins

Unit: mm
	AR 33501	AR 33201
Outside diameter of gudgeon pins "a"	20.996 ÷ 21.000
Clearance between gudgeon pin and seating on piston	0.004 ÷ 0.012

02 Maintenance