Cleaning

1 Remove all traces of old gasket material from the cylinder head of Fiat Punto. Proprietary solvents are available for this purpose, but satisfactory results can be achieved by using a hard plastic or wood scraper to remove all traces of gasket and carbon.
2 Similarly, remove the carbon from the combustion chambers and ports, then wash the cylinder head thoroughly with paraffin or a suitable solvent.
3 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

Cylinder head

4 Inspect the head thoroughly for cracks, evidence of coolant leakage, and other damage. If significant defects are found, a new cylinder head should be obtained.
5 Use a straight-edge and feeler blade to check that the cylinder head gasket surface is not distorted. If it is, it may be possible to lave it machined, provided that the cylinder head thickness is not excessively reduced. As no specifications of permissible distortion limits or cylinder head thickness tolerances are given by the manufacturer, seek the advice of an engine reconditioning specialist if distortion is apparent.
6 Examine the valve seats in each of the combustion chambers of Fiat Punto engine. If they are severely pitted, cracked, or burned, they will need to be renewed or recut by an engine reconditioning specialist. If they are only slightly pitted, this can be removed by grinding-in the valve heads and seats with fine .give-grinding compound, as described below.
7 Check the valve guides for wear by inserting the relevant valve, and checking for side-to-side motion of the valve of Fiat Punto engine. A very small amount of movement is acceptable. If the movement seems excessive, remove the valve. Measure the valve stem diameter (see below), and renew the valve if it is worn. If the valve stem is not worn, the wear must be in the valve guide, and the guide must be renewed. The renewal of valve guides should be carried out by an engine reconditioning specialist, who will have the necessary tools available.
8 If renewing the valve guides, the valve seats should be recut or reground only after the guides have been fitted.

Valves

9 Examine the head of each valve for pitting, burning, cracks, and general wear. Check the valve stem for scoring and wear ridges.
Rotate the valve of Fiat Punto, and check for any obvious indication that it is bent. Look for pits or excessive wear on the tip of each valve stem, Renew any valve that shows any such signs of wear or damage.
10 If the valve appears satisfactory at this stage, measure the valve stem diameter at several points using a micrometer. 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.
11 If the valves are in satisfactory condition, they should be ground (lapped) into their respective seats, to ensure a smooth, gas-tight seal. If the seat is only lightly pitted, or if it has been recut, 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 a specialist, to decide whether seat recutting, or even the renewal of the valve or seat Insert (where possible) is required.
12 Valve grinding is carried out as follows, with the head supported upside-down on blocks.
13 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.



Grinding-in a valve


14 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.
15 When all the valves have been ground-in, carefully wash off all traces of grinding compound using paraffin or a suitable solvent, before reassembling the cylinder head of Fiat Punto.

Valve components

16 Examine the valve springs for signs of damage and discoloration. Stand each spring on a flat surface, and check it for squareness. If any of the springs are damaged, distorted or have lost their tension, obtain a complete new set of springs. It is normal to fit new springs as a matter of course if a major overhaul is being carried out.
17 Renew the valve stem oil seals regardless of their apparent condition.