Alfa75 project

In 1996 I bought an Alfa75 1.8IE, 4 years old and 19.000 kms.  Running on LPG, it now has a mileage of 345.000 kms and the engine starts to give up. It runs hot, smokes badly when idling and oil pressure is low. Can’t blame the car I think, but I had to think about an alternative.

Because I drive 40.000 kms a year, it had to be either LPG or diesel. And as a board member of the Dutch Alfa75 register within the Dutch alfaclub S.C.A.R.B. it also had to be an Alfa75 again, in my opinion the last real Alfa Romeo. Looking around it showed to be difficult to find a cheap one on LPG with little mileage, and a diesel was even harder to find in Holland.

The Alfa 75 project starts

So I got the idea of overhauling the car so that I could drive it another 6 years or so. It would be nice if the output power was also a bit increased. Could I make it a 2-liter instead of 1800cc? Iron cast engines normally are bored up to increase the displacement, but this is not possible with the Alfa light-alloy engines with wet cylinder liners. Just fitting 2-liter liners won’t be a solution because the cylinder positions differ. A 2-liter TwinSpark engine would be an option, but having a spare 2.0IE engine from an Alfetta QO and new pistons and lines for that I decided to modify it so that it could be used in an Alfa75. Technically spoken it is the same as up-boring the cylinders to 2000 cc.

Overhaul work

The overhaul is done by Mannessen Engines (Soesterberg, Holland) who has a lot of experience with Alfa Romeo engines. In fact the owner is a former employee of Savali (Sam van Lingen, Holland) who is a well-known Dutch Alfa tuner. He knows a lot of tricks and modifications to Alfa engines to have them run even better than when they left the production plant. Other makes for which he does the overhaul are Jaguar, Rolls-Royce and Maserati.

On the 2-liter engine, following work has been done:

• cylinder head overhaul with new valve seats and guides
• milling the cylinder head to increase compression ratio
• balancing pistons, push rods, crankshaft, flywheel and crankshaft pulley
• decreasing flywheel weight
• line boring the engine block
• fitting new big end and main bearings
• liner honing using a torque plate

Line boring

Once an engine has been cast, it still contains a lot of mechanical strains, which will be gradually released during the first 100.000 kms or so. This results in more or less severe deformation of the engine block. Bearing wear will compensate for this. However, if new bearings are fitted, it may show up that not all main bearing free play is equal on all bearings, or worse, the crankshaft shows heavy points when rotating. Especially the front and rear main bearing tend to hammer out a bit by external forces on pulley and propshaft.

The best solution is to line-bore the engine block again. As a result the bearing free play values can be chosen much smaller which results e.g. in a higher oil pressure. Mannessen Engines aims at the highest quality for engine overhaul and invested in own line bore equipment, which distinguishes them from other engine workshops. Some of the pictures on this site show my engine clamped in the line-bore machinery.

The line-boring process starts with milling down the main bearing caps for about 0.01 mm. Putting the caps back on the engine, the bearing hole in fact has become a kind of rugby ball. Then a large hone drill with precisely variable diameter is run through all bearings until the aimed bearing size has been achieved. The result is an engine block with exact main bearing bore diameters and no mechanical strains left.

Torque plate

Especially on light-alloy engines with wet liners like the Alfa Nord engines, new liner bores have a tendency to become slightly oval when the cylinder head nuts are tightened. Therefore Mannessen Engines uses a precisely flat, thick iron torque plate that can be fitted on the engine block, whereafter the liners can be honed round again. One picture shows such a torque plate. Using this kind of special equipment is also not common practice, but is part of the quality level of Mannessen Engines.

LPG

In this project I would like to mention Prins Autogas Systems (Veldhoven, Holland), who were very helpful in overhauling the LPG system.