Clikadjust - Why use It?

Valve Actuation
The diagram below shows the essential components of a valve actuator. The pushrod rises and falls by action of the camshaft and in doing so, moves one end of the rocker arm upward too.  The rocker is pivoted on its shaft so that upward movement on one end (right) results in downward movement toward the valve stem against the force of the valve spring that is pushing the valve stem upward and tending to keep the valve closed.

Note that when the pushrod is at its lowest there is an expansion gap between the valve stem and the tappet. This gap can be adjusted by means of an adjusting screw that is locked in place by a lock nut. Modern cars don't need a gap, they use hydraulic lifters as part of the pushrod assembly, which are quiet and constantly self adjusting.

Adjustment Using a Feeler Gauge
The normal method of adjusting the tappet is to use a feeler gauge between the rocker arm and the valve stem. This must be done with the pushrod at its lowest point. This is a hard to determine position. The highest point, however, is much more easily recognized, that point is when the valve is fully depressed. For this reason, on a 4 cylinder, 8 valve engine such as in most MG's, the rule of 9 is used. The rule is that:
1. The valves are numbered 1 to 8 from the front of the car.
2. When a valve is fully depressed, its number, subtracted from 9 indicates the valve/rocker that can be adjusted because its pushrod is at its lowest.

So:
Number 1 valve is adjusted when number 8 is fully open.
Number 2 valve is adjusted when number 7 is fully open
Number 3 valve is adjusted when number 6 is fully open
Number 4 valve is adjusted when number 5 is fully open
Number 5 valve is adjusted when number 4 is fully open
Number 6 valve is adjusted when number 3 is fully open
Number 7 valve is adjusted when number 2 is fully open
Number 8 valve is adjusted when number 1 is fully open


The Problem with Using a Feeler Gauge
In reality, the rocker smashes against the valve stem like a hammer on an anvil. It does so 25 times per second at 3,000 rpm. Although both are hardened steel, eventually the rocker and the valve stem wear, necessitating adjustment by means of the adjusting screw. Unfortunately, the rocker arm, which to account for tolerance build up is larger than the valve stem, tends to suffer concave wear to the centre its active surface.

To adjust a valve clearance, a feeler gauge is usually placed between the valve stem and the rocker.
As shown in the picture at left, when the rocker has worn, the measured gap, which is the thickness of the feeler gauge, is less than the actual gap, the feeler gauge failing to measure the concave wear point. This results in the valve opening less than it should, (adversly affecting performance), slightly off valve timing and above all, very noisy tappets.
 
 
 


The Clikadjust Method
The Clikadjust method of tappet adjustment does not use a feeler gauge, instead the adjusting screw is tightened to a known point; that where the gap is zero. The tool design ensures that lock-nut remains backed off sufficiently so that it does not restrict the movement of the screw, which might be mistaken for a contact between the rocker arm and valve stem, and give a false zero gap point.

Depending on the pitch of the adjusting screw and the lengths of the rocker arms, each degree it is backed-off, corresponds to a certain increase in tappet gap. The Clikadjust is a specialized screwdriver that provides an audible click for every 1/30 (12° ) of a full turn so that for a given rocker arm and adjusting screw, a given number of clicks equates to opening the gap from zero to a certain gap distance.


Calibrating the Clikadjust
Once the number of clicks for the correct valve gap is determined for a particular car, there is no need to calibrate again.

However, if the number of clicks is not known for a car, then it may be found by using a feeler gauge. Although a feeler gauge may not be an accurate method of determining absolute gap on a worn tappet, it can measure the difference in gap very well. If we use the example of a 0.015" (15 thou) gap.

Adjust the valve stem to rocker clearance so that a 0.010 (10 thou) feeler gauge can just enter it.

Using the Clikadjust, back off the adjustment screw, counting the clicks, until it can accept the 0.010" feeler gauge plus the required gap; in this example that's 0.010 + 0.015 = 0.025 (or 25 thou). The number of clicks counted is the required information.

Make a note the number of clicks ready for next time.

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