Rebuilding the twin-cam: Part Two

So… As I might have mentioned in my last post, many components of my twin-cam 1600 were damaged beyond salvation by the time it landed in my garage. It took a bit of asking around, but eventually I came across all the replacement parts I needed. From the crank, all the way up to the cams, everything had to be replaced.

Once I had all the moving parts for the lower end of the engine (crankshaft, pistons, con-rods and fly wheel) I sent them all off to Durban to be balanced. This, however, took more than a month and a half.

Once I got the parts back, my first installation attempt showed up a huge problem with the new crank. It seized up solid once I tightened up the main bearing caps. This meant the engine had to go straight to the engineers, to find out where the issue was. It turned out, it was just a slight distortion of the bearing caps, and nothing too serious. The caps were bored out and now work very well.


The new crankshaft, installed with freshly re-machined bearing caps and bearings.


The crankshaft pulley had to be re-sleeved as it was cracked along the key-way. The old timing chain gears, fortunately, could be saved with a bit of wire-brushing. Here they are installed with a new lower timing chain.


This gear on the crank must be removed in order to install the lower chain. I wish I’d known this before I started.


These three 0s must point towards each other at Top Dead Centre.


The fly-wheel is the original one out of my car, I’ve just had it skimmed to ensure there’s a good surface for the friction plate to work on.


The starter-motor ring-gear was too worn, so this one is a replacement.


Here are some of the holes made in the balancing process.


Crankshaft big-end journals looking very smooth.


A drill hole in the counter weight of the crankshaft.


The old crank with deep rust pitting.


New 2000GTV cams, along side the old standard 1600 cams.


Nice and smooth.


Not so smooth.


Some good 2nd hand cam-followers and shims.


And some good 2nd hand cam bearing caps.

There have been some issues fitting new parts to the engine, as this is such an early 105 engine, that many available parts don’t fit, as the market caters more for the more common, later models.

The new oil pump for my car was too tall for the early, short oil pan which was fitted to Sprint GTs. This meant I had to find a tall oil pan from a later car.


Here is the engine with the tall oil pan fitted.


Here you can see the difference between the early short pan, and the later pan.


There’s about 10mm between the two oil pans.

The gearbox in my car is from a later car. It’s still a mechanical-clutch box, and the only difference between the Sprint GT box and this one is the way the reverse gear is engaged. The early box has a “push down” reverse gear, and this one has a little spring plate which prevents you from shifting from 5th into reverse.

Another issue, is that the later bell-housing has three bolt-holes for the starter motor, whereas my early starter has only two bolt-holes. This also causes another problem; The crank-case breather, which is on the rear of the block, gets blocked by this slightly taller bell-housing, and the breather tube is displaced by that third starter bolt-hole.

I imagine this is why the breather was altogether missing from the engine when I got it. So, I had to have a new one made up from scratch. And I had bell-housing machined down to Sprint GT specs.


The extra bolt-hole.


This protrusion blocks the path of the crank-case breather.


The taller top lip of the bell-housing blocks off the location of the breather.


The shortened bell-housing leaves room for the new breather.


Without the third bolt-hole the breather pipe sits in the correct position.


Now the bell-housing matches up with the starter.

Now, all that’s missing is the cylinder head. It’s been with the engineers since November, and I hope to have it back soon. The rest of the engine parts are sitting about, all ready to go. But my wait for the cylinder head continues.


Distributor and fuel pump.


Water pump and oil pump.


Very many gaskets and seals.


Carbs ready to go.


Cylinder head nuts, without a cylinder head. My kingdom for a cylinder head….



1 Comment

  1. […] tea has gone into the Alfa’s little twin-cam. The cylinder head which was so sorely missed in Part 2 was taken back from the engineers who had taken it on (after I discovered , to my horror, they […]

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