A carburetted Alfa twin-cam runs its sweetest when its ignition is set up properly — points, timing and advance all working together. Get it right and the engine is crisp and eager; get it wrong and it runs flat, hot or rough. Here is how the ignition works on the Giulia Spider, and how to give it a proper tune-up.
The system
The Giulia Spider uses a conventional distributor with contact-breaker points (a Marelli unit on most cars), firing the four cylinders in the order 1-3-4-2, with cylinder number one at the front of the engine nearest the radiator and the rotor turning clockwise. The distributor combines mechanical (centrifugal) advance with a vacuum advance to vary the timing with revs and load. This applies to the carburetted cars; it is not the same as the later fuel-injected Spiders, where a computer controls the timing.
Points and dwell
The points are the first thing to check. Set the gap — or, better, the dwell angle — to specification; worn, pitted or misadjusted points lie behind a great many running complaints. Renew them periodically along with the condenser, and keep the distributor cam lightly lubricated. Many owners fit an electronic ignition (such as a 123 distributor or a points-replacement kit) to end points maintenance and hold the timing rock-steady — a popular and usually reversible upgrade.
Timing
With the points set, time the ignition. Bring number one cylinder to its firing point on the compression stroke (cam lobes facing out, timing marks aligned), and set the static timing to the mark for your engine — on a 1600 Giulia Spider this is only a few degrees before top dead centre, but the exact figure varies by engine and specification, so use the workshop manual. Then check the dynamic timing with a strobe light with the engine running, confirming the advance comes in smoothly as the revs rise. Too far advanced and the engine will pink (detonate) and run hot; too far retarded and it feels flat and also runs hot.
Plugs and the full tune-up
Finish with the spark plugs — correct type, gapped to specification, and lightly anti-seized in the alloy head. Ignition is only one leg of a three-legged tune-up: for the engine to run its best, the valve clearances and the carburettors need to be right too. Do all three together and the difference is night and day. The traditional finishing touch — the "Italian tune-up," a few full-throttle runs up through the rev range to clear the plugs and combustion chambers — is exactly what these engines love.
*Written for the Giulia Spider archive. Timing figures, point gaps and plug specifications vary by engine and year — always confirm them against the workshop manual for your car.*