Manual - Chapter 1 Engine

14. Examination and renovation: General

  1. Before any component is examined, it must be cleaned thoroughly. Being careful not to mark or damage the item in question, use a blunt-edged scraper (an old kitchen knife or a broken plastic ruler can be very useful) to remove any caked-on deposits of dirt or oil, followed by a good scrub with a soft wire brush (a brass wire brush of the type sold for cleaning suede shoes is best, with an assortment bottle-cleaning brushes for ports, coolant passages etc). Take care not to remove any paint code marks from internal components.
  2. Soak the component in a solvent to remove the bulk of the remaining dirt or oil. If one of the proprietary engine degreasers (such as Gunk or Jizer) is not available, a high flash-point solvent such as paraffin (kerosene) should be used. The use of petrol as a cleaning agent cannot be recommended because of the fire risk. With all of the above cleaning agents take great care to prevent any drops getting into the eyes and try to avoid, prolonged skin contact. To finish off the cleaning procedure wash each component in hot soapy water (as hot as your hands can bear); this will remove a surprising amount of dirt on its own and the residual heat usually dries the component very effectively. Carefully scrape away any remaining traces of old gasket material from all joint faces.
  3. Check all coolant passages and oilways for blockages, using compressed air to clear them, or implements such as pipe cleaners Note that many of the coolant passages are sealed by core plugs. These are removed by piercing the centre with a hammer and centre punch so that a screw thread can be tapped in and a slide-hammer applied; the plugs should never be disturbed unless absolutely necessary. A hexagon-headed blanking plug is screwed into the underside of the cylinder head to blank off the oilways; if camshaft wear reveal a possible lubrication fault this plug should be removed so that the oilways can be blown clear with compressed air. If it is disturb, tighten it securely on refitting, using a drop of Loctite 242 or similar thread-locking compound on its threads.
  4. If there is the slightest doubt about the lubrication system, for example if a fault appears to have been caused by a failure of the oil supply, all components should be dismantled so that the oilways can be checked and cleared of any possible obstructions. Refer to Chapter 5 - Fuel & Oil for details of the lubrication system. Always use clean, lint-free rag for cleaning and drying components to prevent the risk of small particles obstructing oilways.
  5. Examine carefully each part to determine the extent of wear, checking with the tolerance figures listed in the Specifications section of this Chapter. If there is any doubt about the condition of a particular component play safe and renew.
  6. Various instruments for measuring wear are required, including a vernier gauge or external micrometer and a set of standard feeler gauges. The machine's manufacturer recommends the use of Plastigage for measuring radial clearance between working surfaces such as shell bearings and their journals. Plastigage consists of a fine strand of plastic material manufactured to an accurate diameter. A short length of Plastigage is placed between the two surfaces, the clearance of which is to be measured. The surfaces are assembled in their normal working positions and the securing nuts or bolts fastened to the correct torque loading; the surfaces are then separated. The amount of compression to which the gauge material is subjected and the resultant spreading indicates the clearance. This is measured directly, across the width of the Plastigage, using a pre-marked indicator supplied with the Plastigage kit. If Plastigage is not available, both an internal and external micrometer will be required to check wear limits. Additionally, although not absolutely necessary, a dial gauge and mounting bracket is invaluable for accurate measurement of endfloat and play between components of very low diameter bores - where a micrometer cannot reach. After some experience has been gained the state of wear of many components can be determined visually or by feel and thus a decision on their suitability for continued service can be made without resorting to direct measurement.

14.3 Remove blanking plug from cylinder head to clear oilways, if required