Tappet gap adjustment

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Drawing of rocker The tappet clearance on air cooled VW's is critical for long engine life, performance and fuel consumption. The tappet clearance is the distance required between the valve tip and the valve actuator (rocker). A gap is required to allow for expansion of the valves as the engine heats up. If no gap was allowed between the valve and the rocker, as the valve expanded, the rocker would hold the valve off its valve seat resulting in poor performance, poor fuel consumption and ultimately a burnt out valve. Tappet clearance is all the more important on an air cooled engine due to the extremes of running temperature compared to a water cooled engine. Making the gap to large though will also effect the performance of the engine as the valve will lag behind the camshaft but it is always better to error slightly on the upper clearance gap and have reduced performance compared to a damaged engine.

Setting the tappet clearance is not difficult on a air cooled VW just adequate as the engine is a flat four and under the rear of the van so access (especially for a camera) is not too good!!

Engine The picture shows my 1700 T4 engine but the procedure is the same for all air cooled VW engines but please consult a workshop manual for the exact tappet setting for your engine.

Axle stand Firstly, it is much easier if the rear of the van is raised to gain better access. Make sure that your axle stands are up to the job and place them under the rear axle tube as shown in the picture. Never go underneath any vehicle when supported by a jack alone.

Timing template Remove the mesh cover(3-10mm bolts) to gain access to the crank shaft pulley. Replace the white timing degree template so that you can view the position of the engine. At the same time, highlight the Top Dead Centre (TDC) notch on the crank shaft pulley and also make a second mark 180 degrees around from the TDC mark.

Distributor Cap Next remove the distributor cap to view the rotor arm position. Then using a 13mm socket and 150mm extension turn the crankshaft until the rotor arm is pointing towards the notch in the distributor body (No.1 cylinder) and the TDC notch in the crankshaft pulley is at 0 degrees. At this position, No.1 cylinder is at TDC and both valves are closed and the tappet clearance can be checked.

Removing clip from cover Remove the drivers side valve cover by inserting a screwdriver between the retaining clip and the cover and levering downwards. If you push the clip upwards, it is very difficult to get back into place. Guess how I know??

Rocker assembly You will now be able to view the rocker assembly. The exhaust valves are on the outside edge and the 2 middle valves are inlet valves. The setting for the 2 are different as the exhaust valve requires more clearance as it expands more being in the hot exhaust gas outlet than the inlet valve which is cooled by the incoming petrol. The settings for my 1700 engine are 0.15mm for the inlet and 0.2mm for the exhaust valves. Again, check your workshop manual. Note measurement and adjustment is taken place with the engine cold. The best time to do the work is before the engine has been started.

Adjusting tappets The gap is measured by inserting a feeler gauge of the correct thickness between the valve tip and the rocker arm. The feeler gauge should be a tight sliding fit between the two. If it is not then the clearance needs to be adjusted. Adjustment is carried out by loosening the 13mm locknut and turning the tappet screw in to reduce the gap and out to increase the gap. This is one of those jobs were you need 2 pairs of hands as you have to hold the feeler gauge in place, turn the screw, then tighten the nut to lock into position. At first it seems difficult but after a bit of practice, you soon get the hang of it. When tightening the lock nut the tappet screw usually moves so take care that the gap has not closed up. After tightening, re-check the gap. After checking both inlet and exhaust valves on No.1 cylinder return to the back of the van and turn the crankshaft pulley 180 degrees anti-clockwise until the rotor arm points to No.2 electrode on the distributor cap. Again, follow the procedure for checking /adjustment on No.2 cylinder before replacing the valve cover. After checking No.2 cylinder, the passenger side valve cover needs to be removed to gain access to cylinders 3 and 4 and the crankshaft pulley turned anti-clockwise 180 degrees again. No. 3 cylinder valves can now be adjusted. After adjustment, again rotate the engine 180 degrees anti-clockwise and adjust No.4 cylinder valves.

On completion, replace the valve cover ( always use new gaskets to prevent leaks), distributor cap and the crankshaft pulley mesh cover before starting the engine. Task done until the next 3000 miles is up.

If at anytime you are unsure of anything always seek the help of someone that knows, rather than risk damage to an engine.