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Cylinder head and valve components - cleaning and inspection
Engine removal and general engine overhaul procedures / Cylinder head and valve components - cleaning and inspection


Note: Always check first what replacement parts are available before planning any overhaul operation; refer to Section 1 of this Part. A Ford dealer, or a good engine reconditioning specialist/automotive parts supplier, may be able to suggest alternatives which will enable you to overcome the lack of replacement parts.

1 Thorough cleaning of the cylinder head and valve components, followed by a detailed inspection, will enable you to decide how much valve service work must be carried out during the engine overhaul. Note: If the engine has been severely overheated, it is best to assume that the cylinder head is warped, and to check carefully for signs of this.

Cleaning
2 Scrape away all traces of old gasket material and sealing compound from the cylinder head (see Part A of this Chapter, Section 14 for details).

3 Scrape away the carbon from the combustion chambers and ports, then wash the cylinder head thoroughly with paraffin or a suitable solvent.

4 Scrape off any heavy carbon deposits that may have formed on the valves, then use a power-operated wire brush to remove deposits from the valve heads and stems.

Inspection
Note: Be sure to perform all the following inspection procedures before concluding that the services of a machine shop or engine overhaul specialist are required. Make a list of all items that require attention.

Cylinder head
5 Inspect the head very carefully for cracks, evidence of coolant leakage, and other damage. If cracks are found, a new cylinder head should be obtained.

6 Use a straight edge and feeler blade to check that the cylinder head gasket surface is not distorted (see illustration). If it is, it may be possible to re-surface it.

7.6 Check the cylinder head gasket surfaces for warpage, in the planes
7.6 Check the cylinder head gasket surfaces for warpage, in the planes indicated (A to G). Try to slip a feeler gauge under the precision straight edge (see the Specifications for the maximum distortion allowed, and use a feeler blade of that thickness)

7 Examine the valve seats in each of the combustion chambers. If they are severely pitted, cracked or burned, then they will need to be renewed or re-cut by an engine overhaul specialist. If they are only slightly pitted, this can be removed by grinding-in the valve heads and seats with fine valve-grinding compound, as described below.

8 If the valve guides are worn, indicated by a side-to-side motion of the valve, new guides must be fitted. Measure the diameter of the existing valve stems (see below) and the bore of the guides, then calculate the clearance, and compare the result with the specified value; if the clearance is excessive, renew the valves or guides as necessary.

9 The renewal of valve guides is best carried out by an engine overhaul specialist.

10 If the valve seats are to be re-cut, this must be done only after the guides have been renewed.

Valves
11 Examine the head of each valve for pitting, burning, cracks and general wear, and check the valve stem for scoring and wear ridges. Rotate the valve, and check for any obvious indication that it is bent. Look for pits and excessive wear on the tip of each valve stem. Renew any valve that shows any such signs of wear or damage.

12 If the valve appears satisfactory at this stage, measure the valve stem diameter at several points, using a micrometer (see illustration). Any significant difference in the readings obtained indicates wear of the valve stem. Should any of these conditions be apparent, the valve(s) must be renewed.

7.12 Measuring the diameter of a valve stem - if any significant difference
7.12 Measuring the diameter of a valve stem - if any significant difference is found in the readings obtained, excessive valve stem wear is indicated

13 If the valves are in satisfactory condition, they should be ground (lapped) into their respective seats, to ensure a smooth gastight seal. If the seat is only lightly pitted, or if it has been re-cut, fine grinding compound only should be used to produce the required finish. Coarse valve-grinding compound should not be used unless a seat is badly burned or deeply pitted; if this is the case, the cylinder head and valves should be inspected by an expert, to decide whether seat recutting, or even the renewal of the valve or seat insert, is required.

14 Valve grinding is carried out as follows.

Place the cylinder head upside-down on a bench, with a block of wood at each end to give clearance for the valve stems.

15 Smear a trace of (the appropriate grade of) valve-grinding compound on the seat face, and press a suction grinding tool onto the valve head. With a semi-rotary action, grind the valve head to its seat, lifting the valve occasionally to redistribute the grinding compound (see illustration). A light spring placed under the valve head will greatly ease this operation.

7.15 Grinding-in a valve seat - do not grind in the valves any more than
7.15 Grinding-in a valve seat - do not grind in the valves any more than absolutely necessary, or their seats will be prematurely sunk into the cylinder head

16 If coarse grinding compound is being used, work only until a dull, matt even surface is produced on both the valve seat and the valve, then wipe off the used compound, and repeat the process with fine compound. When a smooth unbroken ring of light grey matt finish is produced on both the valve and seat, the grinding operation is complete. Do not grind in the valves any further than absolutely necessary, or the seat will be prematurely sunk into the cylinder head.

17 When all the valves have been ground-in, carefully wash off all traces of grinding compound, using paraffin or a suitable solvent, before reassembly of the cylinder head.

Valve components
18 Examine the valve springs for signs of damage and discolouration, and also measure their free length by comparing each of the existing springs with a new component.

19 Stand each spring on a flat surface, and check it for squareness (see illustration). If any of the springs are damaged, distorted, or have lost their tension, obtain a complete set of new springs.

7.19 Check each valve spring for squareness
7.19 Check each valve spring for squareness

20 Check the spring upper seats and collets for obvious wear and cracks. Any questionable parts should be renewed, as extensive damage will occur if they fail during engine operation. Any damaged or excessively-worn parts must be renewed; the valve spring lower seat/stem oil seals must be renewed as a matter of course whenever they are disturbed.

21 Check the hydraulic tappets as described in Part A of this Chapter, Section 13.


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