Rotor position for static timing

[tspin]

I have a 73 Sport Coupe with a 79 1995cc engine (carburated). I had the cylinder head reconditioned over the winter and plan to reinstall it soon and want to make sure I get the static timing right. When I align both camshaft timing holes with the pointer tips both valves on cylinders 1 and 4 are closed. If I mount the head like this with the crank pulley set at 0 TDC (the long mark) and install the timing belt do I point the distributor rotor at cylinder 4?

I see this referred to often but also see reference to pointing the rotor to cylinder 1 from time to time. Which is it?

Also with the above and rotor pointing to cylinder 4 should the points just have closed?

Thanks in advance for any guidance

[spider2081]

When the ignition points are closed the coil is building a magnetic field. When the points open it collapses and creates the high voltage for the spark. when smoking was common we used the match book cover to set point gap. Then place a thin paper like cigarette pack wrapper to set the open point. Place the paper between the closed points and gently pull on it. Then rotate the distributor until the paper is free. I believe Fiat Spider static timing is set when the rotor is pointing to #4 and points are just opening.

[18Fiatsandcounting]

On all the 124 coupes and spiders that I've had, when the timing marks on the two camshafts are lined up, and the engine is at TDC, it is cylinder #4 that would be firing at that point. Actually, it would have just fired a few degrees of crankshaft rotation earlier (5 to 10 degrees), but close enough. So, with the cams and crankshaft set like this, I align the distributor so that the rotor is just about to reach the distributor cap internal contact for the #4 cylinder, and the points have just opened.

Spider2081 is correct about the points, and to elucidate further, the magnetic field builds up in the primary winding (low voltage side) of the coil when the points are closed. When the points open, that magnetic field collapses but the energy has to go somewhere, and so it induces a very high voltage (but low current) in the secondary winding of the coil, resulting in the spark at the spark plug. The collapse of the magnetic field also induces a voltage across the primary winding of the coil, which is not good as the points would tend to spark themselves and thus corrode, so a capacitor (condenser) is placed across the points to "smooth out" the energy reintroduced into the primary winding of the coil.

More than you wanted to know perhaps, but there you have it! Also, very important, don't forget to check that the auxiliary shaft is also lined up. Similar to the camshaft pulleys, it also has a small hole about an inch or two outward from its center axis, and that small hole should be about 40 degrees clockwise from the top (looking at the engine from the front), when the camshafts and crankshaft are lined up as above. It's not critical, but if this timing is way off, some parts can hit internally as the engine rotates.

-Bryan

[redcars]

+1 on Bryan

[tspin]

Great, thanks very much for the excellent and detailed advice.