This is the order I like to do it but its not set in stone. Generally I like to start at the top and work down.
Remove the air filters
Disconnect the carburettor linkages, also the linkage in front of the fan housing.
Remove the fuel lines to both carbs and at fuel pump end. Remove fuel line. normally you should need a 17mm wrench/spanner.
Remove carburettors. should be 12mm nuts. Be careful you do not damage the idle mixture screw or accelerator pump linkage undoing these. Remove carbs.
Undo generator nut and remove fan belt and washers. Check generator spins freely.
Remove wires from coil.
Remove oil lines from oil filter can.
Remove generator tie down strap. keep special nut and bolt in safe place.
Remove thermostat rod which comes through fan housing. it unscrews by turning the rod counterclockwise.
Remove bolts holding fan shroud to engine. Normally 10mm but have often been replaced by cheese head screws
Remove the 3 bolts each side that hold the spring plates of the cross linkage bar attached to the sides of fan shroud. Remove the cross linkage bar.
You should now be able to lift of the fan housing complete with the generator, oil filter can and coil still attached. (Yes I know the coil is upside down!!)
Now is a good time to tackle the exhaust. It should be held to the cylinder head by 12mm nuts but these are often 13 or even 14mm. You may need the WD40. Sometimes the stud will come out with the nut which is ok as a VW stud will fit and are easy to come by.
If all else fails cut the exhaust.
Remove fuel pump supply line.
Now you can start removing the sheet metal screws using a large screwdriver. Remove the rubber seals. Its not a bad time to take a photograph so you remember exactly how the sheet metal goes.
Remove the fuel pump - it is held by two 14mm bolts.
Remove the J tubes and heater boxes.
Remove the spark plugs.
Remove the carburettor manifolds. One bolt and two nuts. Bolt is special so do not lose it. Normally it is 14mm.
Remove rocker cover and the bale that holds it in placeCheck your rocker stand. Supers should have an aluminium stand with the rockers held by saddle washers and nuts. Normals have a cast stand with circlips holding the rockers. Photo below shows a super with saddle washers as original and lock nuts which are incorrect.
Loosen the tappet adjusting nuts as its easier now than when disassembled. Note that the tappet adjusting nuts and the rocker tie down nuts look very similar but do not confuse them as they are different threads
Loosen the nuts holding the rockers. the exhaust rockers at each end are held by 2 nuts, the intake rockers in the middle by 3 nuts.
Remove push rods from their push rod tubes.
Remove the 15mm bolts holding the rocker stand to the cylinder head.
Remove the stand. Check it for cracks
Remove the head bolts using a 10mm allen socket. loosen evenly starting in the middle and working out. There are 8 in total each side.
Remove the cylinder head. The photo shows the eight bolts, four next to the valve springs and four recessed into the cooling fins above.
Remove the push rod tubes and the air deflector plate which is held to the cylinders with a wire spring. This photo shows the black deflector plate, push rod and spring. Note that early push rod tubes did not have the one inch extension that the later tubes have. the long end goes into the case.
Keep these parts safely.
Remove the cylinders to expose the pistons. The pistons are held to the connecting rods by a wrist or gudgeon pin which is held in place by circlips.
Remove the circlips that hold the wrist or gudgeon pins of the piston. you will need circlip pliers for this.
Use a drift to remove the pins. an old 1/2" socket set extension bar is often the right size. If the pin is very stiff you can gently heat the piston for 30 secs or so with a blowtorch or even the heat from an old fashioned light bulb and usually this sorts the problem.
Remove the pistons for inspection later.
Now is a good time to drain any oil left in the sump. Remove the oil sump plate which is held by 10 nuts and washers. It is not unusual for a stud to come out when removing the nuts but it can easily be put back in by using the double nut technique. This involves putting 2 nuts on the stud, tightening them against each other and using the outer nut to screw the stud back in.
Remove the sump plate and filter. The sump plate has a magnet in the middle - check this for metal pieces, bronze and metal filings indicate wear in the engine.
Next remove the gauze filter which has a central hole for the oil pick up pipe.
Rock the engine from side to side to remove all the oil.
The next task is tricky. It is removal of the flywheel nut. If the clutch pressure plate is still fitted you will need to remove this first. It is held by six bolts and it is best to release them slowly a little at a time working around the plate. Eventually it will come off. Inspect and discard or keep for reuse if you feel there is life left.
For the flywheel nut you will need a 1/2" 36mm socket and a breaker bar. You will need to lock the flywheel. In the picture below is a long handled breaker bar with 36mm socket. Note the flywheel lock bolted to the engine case. The flywheel locks are a VW product and fit the 1800mm flywheels. They can be bought at most air cooled vw outlets and on eBay. Both the photos were taken with the engine on the bench for illustrative purposes. Your engine will need to be firmly attached to your engine stand or bench support.
Flywheel nut and flywheel lock
The next picture shows the pulley nut with a 30mm socket. again a breaker bar may be required. The nuts can also be removed using an air ratchet but it has to be a powerful one.
You can now repeat the process for the pulley. Remove the pulley nut and gently tap the pulley off. Use a piece of timber to avoid metal to metal if it is stubborn. If you look closely at the pulley shaft with the pulley removed you will see there is a semi circular shaped key in the shaft. lever this out and keep it safe.
You can now remove the pulley shroud tinware. It should be bolted to the third piece with two 6mm long short bolts. They are shorter than the usual tin ware bolts. Check they are the short ones and keep these aside in a separate bag clearly marked.
It is now possible to remove the oil pump cover. The "A" engines up until mid 1959 had a small oil pump. It was then replaced by the more efficient larger one. Remove the 4 nuts holding the cover (3 nuts and a special bolt on later large ones). In the picture below the early style oil pump cover is being removed by inserting 2 bolts into the threaded holes in the cover and tightening them which forces the cover off. This system was discontinued on later engines. Note the early style 5 bolt seal ring which covered the pulley seal. this was discontinued in mid 1957.
The gears can now be removed and inspected for wear.
Check the gears and oil pump drive shaft that is driven by the cam for wear. If the slot in the cam or the end of the gear show signs of wear then replace the worn components.
Next remove the oil cooler and associated oil fittings from the top of the case. The early oil coolers are held by two 6mm studs attached to the cooler and a nut on a stud attached to the case. The later oil coolers had 8mm studs. In the photo below the stand for the oil cooler can be seen towards the front (flywheel) end of the engine with the stud and nut that holds the right side of the cooler and the holes for the studs of the cooler on the left. The middle two holes are where the oil enter and leave the engine.
Oil cooler base showing stud, stud holes and oil entry points with seals
Remove the fitting for the oil line to the rear (pulley) end of the engine as you will not be able to remove one of the perimeter bolts if you don't. Remove any other oil line fittings
It is now time to remove the oil pressure relief/control valve. Engines up to mid 57 only had one located on the third piece. It is easy to identify as it has a large brass cap with a wide Flathead screw socket on its surface. You need a wide screwdriver to undo this. Be careful not to damage the cap. Once unscrewed you can remove the spring and plunger. However it is quite likely that the plunger will be well and truly stuck and a special tool is available to remove the plunger. This is the tool on the right in the photo below. These can be obtained from VW heritage in the UK of Pelican in the USA
Later engines (57.5 onwards ) had 2 oil pressure relief/control valves, one in the third piece and one in the left hand case half. Remove both. Between mid 1957 and mid 58 a third thermostatic oil control valve was also fitted to the left side of the third piece. This was not a success and Porsche recalled the engines and removed the workings of the valve and capped them off!!