Parts known to be different:
What is needed to get it to fit
What is needed to get the engine to work?
We need to separate this as well, as first you need to plumb everything in, connect everything etc, then you need to worry about fuel and ignition systems. Lets look at the nuts and bolts issues here, and refer to the Fuel System and Ignition System sections for those issues.
The block of the 16v is virtually identical to the 8v engine, and as such many of the hoses, the thermostat housing, water distribution block and alternator brackets were taken straight from my 1.5 8v twin carb engine. There are, however, some differences, some due to the 16v engine, some due to my decision to fit throttle bodies. All the heater hoses are a direct fit. The radiator will fit into its usual place, but as mentioned above, the fan needs to be modified or exchanged with an aftermarket item. The only problem with the radiator itself comes from the position and shape of the bottom hose. Refer to the coolant system section for details.
On my installation the top hose is a tight fit due to the throttle bodies being slightly larger than the original carbs, but it does go in. I elected to use the 16v hose, cut down slightly for this as it gave 2 to 3 mm extra clearance for the throttle bodies. This is not essential though.
The chassis rail to engine block steady located on the right hand side fits without a problem, though I will be installing new bushesMy 1.5 8v had an oil cooler fitted, with a thermostatically operated adapter plate fitted between the oil filter and its mounting pad. This fits straight onto the 16v. A picture can be found on fig 8, and can also be seen in fig 1.
The starter of the 16v is of a different design, as the location of the ring gear on the flywheel is further forward than on the 8v due to the inclusion of the 60 - 2 toothed wheel on the rear. The 8v starter can be used in conjunction with an adapter plate.
The alternator brackets will need washers between them and the block, and the alternator itself will need shimming between it and the water distribution block, as the water pump pulley on the crankshaft sits marginally forward of the 8v position. Other than that, location and fitment is identical.
Get the dipstick from the 16v engine, or else you will have to bush the dipstick hole for the 8v dipstick.
The clutch slave cylinder fits in identical fashion to the 8v into the rear crankcase cover.
Apparently some 16v engines come with distributor-less ignition from the factory, in which case there is a possibility that the top of the oil pump drive does not have the keyway for the distributor drive machined into it. I think that this is unlikely, as this would mean Alfa changing the design of the pump, but it is possible. Should this be the case and you need to use a distributor, you can fit one of the earlier oil pumps with the keyway. It is a direct fit.One curious item is the brake servo vacuum hose connection into the inlet manifold. As the manifolds are identical apart from this detail, it means that the one that has the connector can be fitted on either side of the engine. Strangely, though, it seems that if you fit it on the same side as the existing servo pipe (right hand head), it points forwards instead of rearwards. If you fit it on the left hand head, it points rearwards. Whichever way, you will have to modify and extend the servo pipe. My preference was for fitting it on the left hand head and running the longer pipe along the bulkhead. It is not a difficult problem to overcome though.
The exhaust manifold bore where it joins the rest of the system is 47mm approximately, and the outside diameter is around 51mm. I got lucky in that the (bloody expensive) Ansa system that is fitted to my car has a 47mm outside diameter portion where it joined the old 8v manifold. It will need cutting back by and inch or so, but it is a nice sleeve fit into the 16v manifold, so my immediate worries are over. I will say, though, that the centre section of the Ansa system is a bit weedy at around 42mm, so I will probably change this at a later date. There is a possibility that this will cause excess back pressure due to the restriction. However, if you were not lucky, you would have two options; either fit a reducer section to get the diameter down to the right size, or use a big bore exhaust system, with an adapter pipe. There are a number of 2 inch diameter systems out there that would probably suit very well.
The water temperature sender, oil pressure switch and oil pressure sender all appear to be compatible with the 8v wiring, but in the case they were not, you would be able to install the 8v sensors.