- Published: 29 September 2013
Valve clearance of Fiat Punto - check and adjustment
Note: The following procedure is not applicable to DOHC (16-valve) engines which utilise self-adjusting hydraulic tappets.
1 The importance of having the valve clearances correctly adjusted cannot be overstressed, as they vitally affect the performance of the engine. Adjustment should only be necessary when the valve gear has become noisy, after engine overhaul, or when trying to trace the cause of power loss. The clearances are checked as follows. The engine of Fiat Punto must be cold for the check to be accurate.
2 Apply the handbrake then jack up the right-hand front of the car and support on an axle stand. Engage 4th gear. The engine of Fiat Punto can now be rotated by turning the right-hand front road wheel.
3 Remove all spark plugs.
4 Remove the camshaft cover.
5 Each valve clearance must be checked when the high point of the cam lobe is pointing directly upward away from the cam follower.
6 Check the clearances in the firing order 1-3-4-2, No 1 cylinder being at the timing belt end of the engine. This wilt minimise the amount of crankshaft rotation required.
7 Insert the appropriate feeler blade between the heel of the cam and the cam follower shim of the first valve (see illustration). If necessary alter the thickness of the feeler blade until it is a stiff, sliding fit. Record the thickness, which will, of course, represent the valve clearance for this particular valve.
Checking a valve clearance with a feeler blade
8 Turn the engine of Fiat Punto, check the second valve clearance and record it.
9 Repeat the operations on all the remaining valves, recording their respective clearances.
10 Remember that the clearance for inlet and exhaust valves differs - see Specifications. Counting from the timing belt end of the engine, the valve sequence of Fiat Punto is:
11 Where clearances are incorrect, the particular shim will have to be changed. To remove the shim, turn the crankshaft until the high point of the cam is pointing directly upward. The cam follower will now have to be depressed so that the shim can be extracted. Special tools are commercially available to do the job, otherwise you will have to make up a forked lever to locate on the rim of the cam follower. This must allow room for the shim to be prised out by means of the cut-outs provided in the cam follower rim (see illustration).
12 Once the shim is extracted, establish its thickness and change it for a thicker or thinner one to bring the previously recorded clearance of Fiat Punto within specification. For example, if the measured valve clearance was 1.27 mm too great, a shim thicker by this amount will be required. Conversely, if the clearance was 1.27 mm too small, a shim thinner by this amount will be required.
13 Shims have their thickness (mm) engraved on them; although the engraved side should be fitted so as not to be visible, wear still occurs and often obliterates the number. In this case, measuring their thickness with a metric micrometer is the only method to establish their thickness (see illustration).
14 In practice, if several shims have to be changed, they can often be interchanged, so avoiding the necessity of having to buy more new shims than is necessary, but do not turn the engine with any shims missing.
15 If more than two or three valve clearances of Fiat Punto are found to be incorrect, it will be more convenient to remove the camshaft for easier removal of the shims.
16 Where no clearance can be measured, even with the thinnest available shim in position, the valve will have to be removed and the end of its stem ground off squarely. This will reduce its overall length by the minimum amount to provide a clearance. This job should be entrusted to an engine reconditioning specialist as it is important to keep the end of the valve stem square.
17 On completion, refit the camshaft cover, and the spark plugs.
18 Lower the car to the ground.