After a few weeks of anticipation while waiting for crucial parts, these finally started to arrive last week. The longer ARP studs for the intake manifold, the thread sealing paste and lubricant for its assembly, plus the crankshaft pulley and crankshaft locknut. The dowels for the cylinder head and the gearbox were also supplied.

Why should I (and you) use a thread sealing paste when using ARP studs? I received a very good explanation from Paul Vanderheijden:

In Fiat 850 engines (and their derivatives) the head bolts are in contact with the cooling water channels. These head bolts are tensioned in the block. When the engine is running, the oil pressure (350 to 550 kPa) provides enough pressure in the bolt hole to prevent coolant from creeping up through the threads. When you switch off the engine, the oil pressure drops and the pressure from the cooling system gets the upper hand. This will cause coolant to want to flow up the thread. If head bolts are mounted, you have the washer and the bolt head to generate enough pressure.
When you use ARP studs, they are not tensioned in the block; they are hand tightened. As soon as the oil pressure drops, the coolant will certainly creep up and mix with the engine oil, resulting in a "nice" sludge. That's why you should always use ARP Thread Sealer (or a comparable product) with ARP studs. The Fastener Assembly Lubricant is put on both sides of the washers and the bottom of the nuts; when tightening, no friction is created that affects the stretch of the stud required to achieve the correct torque.
The advantage of the Thread Sealer is that it does not harden and always guarantees a good seal.


850 arp thread sealer

Of course you can use other sealers (Loctite). However, most of them only reach their effect when they are tightened. This does not work with ARP studs because thethreaded end in the block is not tightened.

The intake manifold studs that were part of my original order were 15mm too short. Without the longer intake manifold studs I couldn't mount the cylinder head as they need to be secured as 5th and 6th. Since ARP's advice is to lubricate all studs with thread sealer, tighten them slightly and then thoroughly clean the top of the block before the head gasket and cilinder head are placed I had to wait until I had everything delivered. Fortunately, Michael from Abarth-Online quickly (within 3 days from Germany!) arranged two longer ones. Now I have enough thread to tighten the intake manifold as well.

850 kopbouten volgorde 850 opbouw (11)

When assembling the front of the engine I got stuck due to the lack of slip rings I thought I needed. On the original 850 engines these are fitted as part of the centrifugal lubrication. I had enough rings in stock, but all of them with an inner diameter that was too small.
850 krusasringen

I assumed these rings were needed on all A112 engines; in the 903cc engines they are, according to my parts book, but in the 965cc and larger they appear not to be necessary. Since no oil flows from the pump to the first main bearing bracket, I have no problem leaving these rings out.

I have quite a lot of crankshaft pulleys in stock, but they all are for engines with centrifugal lubrication. One of them had the correct connection to the crankshaft, but then the crankshaft nut did not fit properly.

Luckily Roel, the one where I bought the engine and the first set of parts, still had a pulley with nut AND he had the sandwich plate for the oil cooler which he had no use for. So I drove to Amsterdam again to pick up the parts and talk about the project. With some insider tips because Roel has built many of these engines!
The sandwich plate for the oil cooler with the longer mounting pipe and hoses are not immediately necessary, but it is nice that I have them already.

850 buit binnen

Since I have chosen to mount the oil cooler, I am not going to use the heat exchanger. It will be for sale later on.

So now I have finally switched from the mock-up phase to the construction phase, although it is getting too cold in my workshop to be working there for a longer period.

The first step was the final assembly of the timing chain and the timing cover (the interior of the engine is already finished). To tighten the camshaft gear you should do the following: mount a ring and a locking ring with a tab that fits into a hole in the sprocket. The other hole fits over the pin in the camshaft:

850 distributietandwiel

My camshaft sprocket has only one hole: for the pin on the camshaft. I tried mounting the washer in various ways and finally came up with the following solution:
In several Fiat 850 engines an "eccentric bush" is mounted on the camshaft. Probably as a counterweight to the drive cam for the fuel pump on the camshaft.
At first I put the washer between bush and camshaft (see top right) but that was not correct. Then I put the ring inside so that the tab fell through the hole (below).
The lip now fits into the hole in the sprocket, after which I could tighten it with 49Nm of torque.

850 nokkenasbus 850 opbouw (5)

It is obvious why the eccentric bush has been given its name.

After that the timing cover with PCV breather can be put on, followed by the crankshaft pulley with nut. At the rear, the cover plate of the cooling system is put back on (with a Staal dealer sticker) and I am ready to mount the flywheel as well.

850 opbouw (6) 850 opbouw (7)

850 opbouw (10) 850 opbouw (9)

As soon as the temperature in my workshop is acceptable again I will continue with the studs and the cylinder head.