Engine/Cylinder block, cylinder head, and crankcase

engine block cylinder ,head and crankcase

This blog provides information about the engine/cylinder block, engine crankcase, cylinder head. The following key components are part of the internal combustion (IC) engine.

  • Engine / Cylinder block
  • Piston
  • Piston rings
  • Piston pin
  • Connecting rod
  • Crankshaft
  • Engine bearing / crankshaft bearing
  • Crank case
  • Engine oil pan
  • Cylinder head
  • Cam shaft
  • Suction & exhaust Valves
  • Valve Timing gear / Timing belt and pulley
  • Inlet manifold & exhaust manifold
  • Gaskets
  • Tappet cover
  • Spark plug (used in petrol / gasoline engine)
  • Fuel injector (used in diesel engine)
  • Fuel supply system
Internal Combustion (IC) Engine components by Knowledge-Swami

Courtesy - Canva
Internal Combustion (IC) Engine components


Engine / Cylinder Block

The function of the engine block is to provides structural support to various engine components and provide structural support to cylinder liners or it acts as an engine cylinder. Engine block consists of a water jacket for engine heat dissipation and it also provides passage for engine oil circulation (for lubrication of engine components)

Engine block/cylinder block also provides structural support to other engine auxiliary components such as,

  • Alternator
  • Starter
  • A/C compressor
  • Coolant / water pump

Engine / cylinder blocks also provide structural support to the gearbox. In modern automotive engine blocks and gearbox are bolted together. For smooth functions of the engine, robust construction of cylinder block is essential. Please watch the following animation about 4 -cylinder engine. Engine blocks must provide support, alignment, position tolerance for all rotating, reciprocating, oscillating components of the engine.

Engine blocks are also fitted with core plugs. Purpose of core plugs to form a leakage-proof cooling system. Core plugs are metal cups, press-fitted, or thread fitting to avoid leakage of engine coolant.

The construction principle of petrol and diesel engine is the same, the only difference is diesel engine cylinder block and cylinder head are more robust in design to withstand high compression ration. Refer to this link to understand the working principle of petrol and diesel engine.

Engine block / Cylinder Block  crankcase- Knowledge Swami.com
Engine / Cylinder Block

Types of Engine block

  1. Monoblock cylinder block: In-line cylinder, V-Cylinder
  2. Individual cylinder
Mono-block CylinderIndividual Cylinder
Better coolant circulation in engine Complex cooling system as each individual cylinder needs to be cooled
Suitable for in-line engineMostly used in V-engine with air cooling
Bulky in handing during maintenanceEasy to handle and replace cylinders
Rigid engine construction as crankcase is integral part of cylinder blockCrankcase cannot be an integral part of cylinder block, so comparatively less rigid construction
Mono-block cylinder Vs. Individual cylinder

Legal & Regulatory Requirements of engine block and cylinder head

It’s a very common practice to punch/engraving an engine serial number on cylinder block. Engine block helps to maintain traceability of the engine and its various key components. It’s also mandatory to provide a serial number of the engine block, it’s the date of manufacturing, casting grade, raw material/heat number, supplier code (if it is procured from multiple sources)

Cylinder Head

Cylinder Head: Cylinder head forms a combustion chamber at the top of the cylinder head. The cylinder head provides a mechanism for camshaft, rocker-arm, valve, valve guide, valve spring.

Types of Cylinder/Engine head:

Types of engine headApplicationSuction ValveExhaust ValveCamshaft Position
Side camshaft Single cylinder diesel gen-set.
Outdated design, as it’s required push rod rocker arm to actuate valves
SOHC2 Wheeler engine / single cylinder engineHeadHeadHead
DOHCMulti-cylinder Petrol / Diesel engineHeadHeadHead
Types of Engine Head

SOHC Cylinder Head – Single overhead camshaft (2 valves/cylinder)

DOHC Cylinder Head – Double overhead camshaft (4 valves/cylinder)

Engine / Cylinder Head details - By Knowledge-Swami.com
Engine / Cylinder Head details

How engine blocks & cylinder heads are made?

Engine blocks & cylinder heads mainly made from aluminum-alloy or cast iron. Most of the car/vehicle OEM procure cylinder blocks from their casting suppliers. Cylinder blocks are manufactured in the foundry and machining is performed at a machine shop.

Engine block & cylinder head material:

Mainly cast-iron aluminum alloy used for manufacturing engine block and engine head. Please refer to the following comparison of aluminum-alloy Vs. Cast-iron block and head.

Aluminum Alloy block & headCast-iron block & head
Lite weight designComparatively heavy in weight
Higher thermal efficiencyComparatively low in thermal efficiency
Comparatively lower strength at high temperature and compression ratio.Good strength at high temperature & high compression ratio
Loss of coolant leads to significant damage to cylinder block and headsHigh resistance to overheating of engine
Less wear resistance – Aluminum alloy block equipped with cast iron cylinder liners (wet or dry liners)High wear resistance – Cast Iron steel can form a cylinder surface.
Higher corrosion resistanceLower corrosion resistance – More prone to oxidation
Higher probability internal threads failure, torque specifications & tightening sequence must be followedComparatively good thread strength, over-tightening of fasteners still can sustain
Suitable for gasoline engineHeavy duty vehicle
Aluminum block Vs. Cast Iron block

What are the key essential Quality assurance and Control required for cylinder block & head?

  1. Control of chemical composition and furnace parameters
  2. Testing of casting test bars for tensile strength, hardness, ductility, elongation.
  3. Verification of casting micro-structure.
  4. Core hardness tester, sand testing, sand moisture testing, permeability test.
  5. Destructive testing of casting blocks per lot.
  6. CMM inspection of key & critical dimensions
  7. Quality control system eg. histogram, 5-Why analysis, Process FMEA, Corrective and preventive action (CAPA) to control casting and machining process.

Please refer following blogs

  1. Who invented the diesel engine?
  2. Types of the engine and it’s working principle
  3. How to maintain a car during lock-down?

We hope this blog was helpful and added knowledge about engine head and block. Sharing is caring!


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