Getting to check the clearances requires removal of the ignition coil cover, 6x coils and spark plugs, and the cylinder head cover. These all come of easily enough.
Ignition coil cover comes off via 4 off M6 caphead screws - retighten to 10Nm on re-assembly. Note strut brace thats needs moving out of the way - easy with my Cosmo.
Remove the 6x coils - 2x M6 nuts each. Undo 2 nuts securing the coil cable channel and lift clear, disengaging the sealing grommet at the very rear of the cly head cover. There is an earth braid at the rear or the rearmost coil - another M6 nut and its off. Take out the 6x spark plugs.
Next its time to remove the cylinder head cover. 20x M6 hex head bolts. You will need to remove 2 cross head screws that secure the cable loom at the rear of the engine compartment. This needs moving around a bit to get access to some of the bolts at the back end.
Cylinder head cover is now ready to be lifted clear. Make sure the shaped rubber seal is not damaged in the process. Break it free from the head and lift it out with the cover.
Revealed - 24v DOHC VVT - lovely jubbely
The clearances are checked with the lobes pointing up, away from the valves. I put the car in first gear and rocket it forwards to turn the engine over to check all 24 off. This works fine, there is no need to turn the crank directly - its a pain to get to.
Check the clearances with feeler gauges. You cant have too many sets for this job. I have 4 sets. More makes checking faster.
Checking the clearances is easy enough but where they are out of range you need to remove the shim and measure it. You need to compress the valve buckets down to do this. The special tool is part number 11 5 070 but dont know if you can buy it and its probably costly.
The correct clearances are 0.28 to 0.33mm exhaust and 0.18 to 0.23mm inlets.
I made my own version of the tool - details here. You will need something like this to do the job. Is not practical to compress the buckets any other way. I made the tool from a plumbing spanner but it could be cut from a smaller piece of steel plate. It needs to be 5mm thick.
The slot you can see in the valve bucket allows a sharp bradawl to be inserted to pop the shim out - see the arrows on TIS pic above.
With the shim out thickness is checked with a micrometer and a note made of the thickness required. Shims are available 2mm to 4.25mm in 0.05 intervals.
Re-assembly is the reverse of the above. The cyl head cover bolts (20x) need tightening to 10Nm. Make sure the cylinder head cover gasket is in good condition and both mating surfaces are completely clean. Refit sparks plugs tightening to 23Nm.
On my car I had 14 valves out of range - 13 needed a shim 0.05mm thinner and one 0.1mm thinner. This indicates that the clearances tend to reduce in time, possibly caused by valve seat errosion. I dont know why this would make the engine noisier on start up though.
I needed 5 new shims to do my car, re-using nine of the existing shims. Shims cost £5 each so the whole job cost £25 plus £9 for a micrometer. It took about 8 hours to do, including making the tool.
After completion the engine sounds lots better on start up. I have the satisfaction of a job well done and I know that all of the valves are within range. You could never be absolutely sure of this from your $dealer.
Good luck!
