Check/Adjust Valve Clearances on a 1980 Porsche 924 Turbo
This guide is for setting valve clearances on a 1980 Porsche 924 Turbo but the overall procedure will be similar for most engines although the adjustment is often made by installing new shims rather than using an adjustment screw.
The first thing to do is align the timing mark on the timing belt pulley (little dot stamped on the side of mine) with the pointer on the valve cover – use a 24mm socket on the crankshaft pulley to rotate the engine.
Then we need to get the upper inlet out of the way.
- Disconnect positive battery terminal – 10mm wrench
- Disconnect inlet boost sensor wire
- Disconnect inlet vacuum line – 2 x 17mm wrenches
- Disconnect inlet ground – 13mm wrench
- Loosen inlet hose clamps x 2 – flat screwdriver
- Undo inlet mounts x 2 – 10mm socket
- Remove inlet by sliding out of the hoses (step 5) towards the passenger side shock tower
Next remove the valve cover
- Mark distributor cap and then rotate out of the way – 13mm wrench
- Remove valve cover nuts x 8 and washers – 10mm socket
- Remove valve cover
Need to find a better pic of valve cover
Now you should see the camshaft and followers, this is a good time to do some visual inspection. Check that the oil splash tube is not bent or damaged, in particular it is important to check that the plastic elbow at the end is in tact – you don’t want this to be leaking and starving your camshaft of oil. You can also inspect the cam lobes for signs of wear or pitting.
Note: the camshaft alignment doesn’t look correct in this picture
If the timing marks were aligned, your camshaft is in position 1 and you should now be able to insert feeler gauges inbetween the cam lobes and the followers of both intake and exhaust on cylinder 1, the intake on cylinder 2 and the exhaust on cylinder 3 and determine the clearances.
I made a table to record all the clearances. Position 1 indicates that the clearance is accessible when the camshaft timing mark is aligned, Position 2 is when the camshaft is rotated 180º.
The service manual for this car gives the following ranges,
Generally it is better to have clearances on the large side rather than too tight. On this car, the followers are solid and have adjustment screws. You can see the adjustment screw through the hole in the follower in the picture above. There are different thicknesses of adjustment screw with larger screws having more ‘notches’ on one end – I think only the largest 4 notch screws are available from Porsche now. The notch end of the screw is shown in the picture above, this screw has 2 notches. The followers can be rotated to get access to each end of the screw; on the other side of the screw from the notches is a 4mm? allen key socket. To tighten the clearance, the screw needs to be screwed further in to the follower by one full turn at a time, each full turn changes the clearance by 0.05mm. There is a special tool available (part number US 8005) to check how far the screw is engaged in the follower.
The tool is inserted into the allen key end of the screw and the edge of the follower should line up in the green region. If the tool goes into the follower up to the flange so that the green region is not visible, the screw is at maximum adjustment and must be replaced by one with more notches – note: the camshaft needs to be removed to replace an adjustment screw. Based on the above picture (many thanks to Ideola on 924board.org), I made up a tool using some insulation tape on an allen key.
Once you’re happy with your clearances, reverse the steps to put everything back together.