Alfa Romeo's 1,570 cc all-alloy DOHC twin-cam is one of the great classic engines — robust, willing and long-lived when maintained. Assessing one is mostly about reading a few honest signals.
Read the smoke
Warm the engine and watch the exhaust:
- Smoke under hard acceleration points to worn bores or piston rings.
- Smoke on the overrun (lifting off after revs) points to worn valve guides.
A little haze on a cold start that quickly clears is far less worrying than persistent smoke under load.
Oil, leaks and noises
Check the oil level and condition, and look around the engine for leaks — some seepage is normal on an old Alfa, but pooling or a heavily oiled block is a flag. Listen for the twin-cam's top end: it should sound busy but even, without heavy knocking or rattling. Combine what you hear with the smoke test and the oil condition to build a picture.
Matching numbers and the 101/105 trap
This is the subtle one. The 101-series and the later 105-series engines and parts interchange freely, so a car described as a "101" can quietly carry later components — or a whole later engine. For originality and value, check that the engine is the correct type and, ideally, that the numbers match the car. It doesn't make a mismatched car a bad buy, but it should be reflected in the price and the description.
The good news
Provided the cooling system has been respected (see the companion cooling article — the twin-cam's real weak spot), these engines are tough and rebuildable, with good parts availability. A healthy one, properly carburetted, is the whole point of the car.