Dismantling the cylinder head

Dismantling the cylinder head

1. Using Fiat valve spring compressor A.60084 or a universal spring compressor depress the valve spring as shown in FIG 1:14 and lift out the cotters. Release the compressor and withdraw the lock cone, oil shield (inlet valve only) upper spring cup, valve spring and lower spring cup. Withdraw the valve from the underside of the head.
2. Dismantle the remaining three valve assemblies as detailed above ensuring that all parts are kept in sets for correct reassembly.

Inspection and servicing of the cylinder head

1. Remove all carbon deposits from the combustion chambers and valve ports using a rotary wire brush or a set of scrapers.
2. Thoroughly clean the cylinder head and to test for distortion lightly coat the machined faces with 'Engineers Blue' or lamp black and place the cylinder head on a surface plate. Carefully slide to and fro and any streaks left behind will indicate a distorted surface. A distorted head will not make a gas-tight seal with the cylinders and must be entrusted to an expert for correction or, in severe cases, renewed.
3. Carefully clean the valve guides as shown in FIG 1:16 using Fiat guide brush A.11417 bis. Should the guides be worn then they should be removed using a press and a suitable sized drift. The guides are press fitted with a pinch fit of .00134 to .00244 inch. To install the guides use Fiat tool A.601 53 as shown in FIG 1:17. As the guides have no stop ring during the press fitting, the depth of insertion is determined by the Fiat tool. If the tool is not available take the necessary depth measurements before the old guides are removed. The normal fit clearance between valve stem and guide is .00087 to .00217 inch with a maximum wear limit of .0059 inch. To check this see FIG 1:18.
4. The valve seats should always be reconditioned after decarbonization. It is suggested that this operation be left to a local service station with valve seat cutting equipment. The valve seat angle for both inlet and exhaust valves is 45° ± 5'.
5. Inspect the valves for soundness or distortion and if the clearance between guide and stem is within the manufacturers wear tolerance of .0049 inch the valve may be cleaned using a wire brush and the seating face ground to an angle of 45°30' ± 5'. This again should be left to the local service station.