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8-valve versions

Early version

Picture 1. Early model TC mounted in the engine compartment of a rear-wheel-drive car.

Early model engines are produced between the years 1966 and 1986. They all look similar, as shown in picture 1. The inlet ports are at the right side of the engine, when viewed from the crank nose. That can be kept as a good identification mark for the old model. In Fiats, the engines are mounted vertically while the Lancia engines are tilted 20 degrees.

The engines can have swept volumes of 1438cc, 1592cc, 1608cc, 1585cc, 1756cc or 1995cc. The first three models have the bore of 80mm and are mainly from the sixties. Those are rare at present, as are the parts for them. Those models were replaced by the 84mm-bore versions that are the latter three models of the previous listing. Generally, the engines have 41.8 diameter intake valves and 36mm exhaust. The exceptions for that are Fiat Regata 100S, Fiat Ritmo/Strada 105TC, Fiat Ritmo/Strada Abarth 130TC, and Lancia Delta 1600GT that have 43,5mm intakes. Turbo and supercharged versions usually have sodium-cooled exhaust valves and bronze valveguides.

Structure of the engine

The cross-sectional drawing of the engine is visible in the picture 2. The intake and exhaust ports are very short and therefore easily reshaped. The intake port forms a kind of a venturi that is located near the valve pocket. This structure is wise to maintain even when preparing the head for race use, since it improves port velocity and low-end performance. Increasing the short-side radius of the intake port turn behind valve is advantageous because it prevents turbulence.

The valvetrain is very simple. This kind of a mechanism does not wear significantly, and therefore, re-adjusting the valve clearances is rarely needed. Also, there is no need to use any problematic and heavy hydraulic valve lifters. Excessive wearing of the camshafts is rare, since they rotate in oil bath.

The 8-valve head permits very big valve sizes to be used (even 49/40mm) without any large modifications to the head (moving the valve guides or something like that). The engine utilizes squish effect between piston and head, and therefore any modifications of the certain areas in the combustion chamber have to be avoided. Nevertheless, the chamber needs no major modifications.

Since the camshafts are operated via toothbelt, their timing is very easily adjusted, individually. The camshafts are located in the separate cam boxes that lay on the head. The camshaft bearings cannot be splitted, and therefore, the shafts must be put in from the end of the box. The diameters of the camshaft bearings limit the maximum lift of the camshaft to 12mm.

Picture 2. Cross-sectional drawing of the engine. Engine is viewed from the crank nose.

The engine has five main bearings and the most models have forged connecting rods and crankshaft as standard. Therefore, quite high output power can be obtained using the standard bottom-end. The engine is extremely compact compared to its power and swept volume, but a good-quality head gasket must be used since the cylinders are close to another. The stock oil pump is good enough, but excessive oil heating must be prevented using an external oil cooler.

The early model TC has a block-mounted auxiliary shaft that runs oil pump and, in certain engines, distributor and fuel pump (as seen in picture 2). Distributor may be also located at the end of a camshaft or on a cam box. This depends on engine model.

Picture 3. Timing belt and shafts. The camshafts are located uppermost, the timing belt tensioner is in the middle and in the lowest there are the crank nose and the auxiliary shaft. The mounting point for a distributor is also visible, but it is blanked off in this case.

One of the greatest advantages of the TC is the similarity of parts. For example, cylinder heads and blocks of all models can be interchanged, as well as the pistons between 84mm-bore models to have the compression ratio needed. Since the valve inclination angle is large, it is not a good idea to remove material from the head to raise CR.

When these things are taken into account, it is possible to raise output power easily.

The fixing points between engine and gearbox are similar in each TC model.

The late model

Picture 4. The late model TC. Note the fuel pump that is located on the cam box.

The TCs of late model are manufactured after the 1985. In all types, the intake ports are on the left side of the engine (viewed from the timing end), and standard valve sizes are 43.5/36mm. Turbo models are equipped with sodium-cooled exhaust valves and bronze valve guides. All of the engines are tilted 20 degrees forward.

The structure of the engine and the engine's tuning potential are quite same as in early-model TC. The most noticeable differences are the crank-nose driven oil pump and therefore, the auxiliary shaft does not exist. As consequence, distributor may be located on the head only. In other respects, the shafts are located same way. Lancia engines usually have two balancing shafts that are described in the story of the 16-valve versions.

Picture 5. Lancia block containing balance shafts. Note the absence of the auxiliary shaft.

The combustion chambers differ from the early model, and the ports are not finished as good as in the early models. That indicates automatic production techniques at factory. The squish bands are widened. This helps to prevent detonation while intake flow is slightly disturbed. The chamber is possible to open out without severely impair squish effect.

The late model head and block are interchangeable with the early models, but the cam boxes must come from the same model as the head. The head gaskets have differential orientation of passages. If heads are used in engines of different tilt, the oil passages of the cam boxes may need modification to maintain the correct oil level for the camshafts. Also the oil pump intake components may need modification.

Picture 6. The late-model combustion chambers. The camber is oval shaped when viewed from bottom, but the use of domed pistons needs bevels at the edges of chambers shown in the picture.

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