Engine - Engine and crankcase
Engine - Static description
The engines are with 4 cylinders ( TT75 ) and 3 cylinders ( TT55 ). Both engines feature cross flow cylinder heads,
with the inlet and exhaust manifolds on opposite sides of the cylinder head. The fuel and air combustion process,
takes place in the specially designed bowel in the crown of the pistons.
Cylinder head assembly
The cylinder head incorporates valves and springs, with the valve rocker arm shaft assembly bolted to the cylinder
block through the cylinder head. Cylinder head retaining bolts are evenly spaced with a six- point pattern around each
cylinder, this ensures an even clamping load across the cylinder head.
The intake and exhaust manifolds are bolted to the head. The intake manifold is mounted on the right-hand side of
the engine, with the diesel injectors mounted outside the rocker cover. The exhaust manifold is mounted on the left
side of the engine.
Water outlet connections and thermostat being attached to the front of the cylinder block directly behind the radiator.
Valve guides are inserted into the cylinder head, and replaceable. Special replaceable cast alloy valve seats are
pressed into each valve port during manufacturing. No over size valve seats on guides are available.
All valves are fitted with positive value rotators, valve clearance is maintained by adjustment of the self locking ad-
justing screw, mounted in each of the rocker arms.
Camshaft assembly
The camshaft runs in 3 replaceable bushes. The camshaft drive gear is in mesh with and driven by the camshaft idler
gear which is driven by the crankshaft timing gear.
Camshaft end thrust is controlled by a thrust plate bolted to the block, and located between the camshaft gear and
the front camshaft journal.
A helical gear is integral on rear of cam shaft, and drives the engine oil lubrication pump mounted forward of the
flywheel.
Cylinder block assembly
The cylinder block is an alloy cast iron with deep cylinder skirts & water jackets for cooling the cylinders. The cylinder
bores are machined integral with the cylinder block, during the manufacturing process. Cylinders are in line and
vertical and numbered from 1 to 3 or 4 from front of the engine to the rear.
The oil sump, which is attached to the bottom of the cylinder block, is the reservoir for the engine oil lubrication system.
A cast iron engine front cover and front plate is attached to the front of the engine and covers all of the timing gear
assembly.
Crankshaft assembly
The crankshaft is supported in the cylinder block by 5 and 4 main bearings in TT75 and TT55 engines respectively.
The crankshaft is manufactured from steel with machined finished crank webs.
End thrust is controlled by a thrust bearing incorporated in the centre main bearing of the crankshaft in TT75 engine
and in the second main bearing from flywheel side in TT55 engine.
A dynamic balancer is fitted and driven by crankshaft to ensure smooth running operation.
Front and rear crankshaft oil sealing is effected by one piece seals that are designed for long and durable service life.
Connecting rods
Connecting rods “Wedge” shaped at the small end has been designed to reduce the reciprocating weight at the piston
end. The connecting rods are heavy beam construction and are assembled as a matched set to each engine, attached
to the crankshaft, by means of insert type bearings.
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