Sump, Crankcase & Crankshaft, Cylinder Block & Pistons

Sumps are different sizes for the various sizes of engines

Bearing Caps, Bearings & Thrust Washers - SERIES I & II TAV. 4

Cylinder Block from Left, Front View with Timing Chest & Cover

SERIES I & II TAV. 2

Cylinder Liners

Cylinder Block from Right, Rear View with Flywheel Cover - SERIES I & II TAV. 3

Crankshaft, Flywheel Piston & Connecting Rod - SERIES I TAV. 6

Crankshaft, Flywheel Piston & Connecting Rod - SERIES II TAV. 6

Flywheels – See Tavs. 6 & 6 bis above

Flywheels

N.B. - See page 01.6/06 et.seq. for details of assembly clearances

1. Three different flywheels are used on Aurelias. The B10 type (B10-1750 changed to 2125854) was also used on the B21, B 22, B15, B50-series and B20 1st to 4th series and B24 4th series.
2. Heavier flywheels were used on the B12 (B12-1750, changed to 2131619) and on the B20 and B24 5th & 6th series (B20-1750, changed to 2129564), and are deeper and required a dished aluminium cover. The earlier type was virtually flat.
3. The heavier flywheel seems more prone to wear on the starter ring with consequent difficulty in starter pinion engagement. Sometimes this problem can be alleviated by moving the flywheel round one hole on its crankshaft mountings, but note that top dead centre will need to be remarked. However as this may unbalance the drive train (all rotating items from crankshaft to gearbox are dynamically balanced and an original set of parts is correspondingly marked with punch marks), it is not to be recommended.
4. All Aurelia (& Flaminia) flywheels have 121 teeth, so each tooth equates to nearly 3º (2.97º). On most Aurelias the distance between the mark ‘AA’ to ‘1/4’ is 4.5 teeth & thus equates to 13º BTDC.
5. The ‘1/4’ mark refers to cylinders 1 & 6 at TDC & not cylinders 1 & 4. It is marked 4 because No. 6 is the 4th cylinder in the firing order & this is why the distributor cap markings match the firing order & not the cylinder numbers. Hence confusion & mis-firing engines!

Pistons

N.B. - See page 01.6/06 et.seq. for details of assembly clearances

1.    Original pistons are expensive and rare if not unobtainable. New pistons are now available in Italy (e.g. Cavalitto) and elsewhere.

2.    Most types of piston have 4 rings all above the pin. The original Borgo and Hepolite types have a 5th ring at the bottom of the skirt. Oil rings on these pistons are 3.5 mm wide rather than the more common 4 mm on other makes of piston.

3.    Oversizes in the bore were 0.2, 0.4, 0.6 and 1.0 mm. The pistons were 0.05 mm less for clearance, i.e. 0.15, 0.35 and 0.55 mm oversize. However, Hepolite pistons were made 0.020 inches and 0.040 inches oversize to fit approx. 78.5 and 79 mm bores.

4.    Some data on pistons: Hepolite: 78 mm + 0.003 inches; Mondiale: 78.4 and 79.0 mm; Borgo:    4/5 rings, one on skirt