Transcript
Hint No. 3. (Thanks again to Ben Courage) IGNITION TIMING. Although the Aprilia engine is a narrow vee formation for owners familiar with conventional straight fours it is reassuring to know that timing principals are exactly the same. This is because the Lancia crankshaft has offset big-end journals which results in the same 180 degree spacing between the pistons arriving at top dead centre (TDC) as is the case for the straight four. If the cylinders are numbered sequentially from the front (the red numbers in the diagram) the firing order is 1-3-4-2, which is the same, as most straight four engines. In their infinite wisdom when the men from Turin wrote the instruction book they caused confusion in two ways: a) They made no. 2 cylinder their reference point, designating it no.1! b) They put the numbers for the firing SEQUENCE on the cylinder head representation in the wiring diagram (see below) As a result the mark for setting a piston at TDC for valve or ignition timing purposes is labeled 1/3 on the timing window--see photo. When the flywheel tooth with the zero or phi mark (which is hard to see and is usefully highlighted with a blob of tippex or similar) is aligned with this mark it is actually no's 2 and 3 pistons that are at TDC. So to check or accurately set the timing assuming that the engine runs or has run with the ignition components as they are: Firstly clean and set the points in the distributor to the correct gap i.e. 0.3 - 0.4mm (12 to 15 'thou). It is best to remove the distributor from the engine to do this because access to the points is otherwise very awkward. Undo the vertical set-bolt (A) rather than slackening the clamp nut/bolt (B) at this stage as this means the distributor can be taken out and refitted without altering the timing. Then crank the engine over by hand until the "zero" flywheel tooth is aligned with the A/A mark (which gives about 11 degrees of static advance). In practice this is most easily done by having the car on level ground, engaging top gear, and pushing the top of the front offside wheel. This way you can turn the engine and watch the flywheel window without mirrors or an assistant!
(I use the starting handle, because the engine turns clockwise the 0 mark is hard to spot, I painted the previous six teeth with red nail polish to make it easier to prevent going past the mark. ngm) Then with the distributor refitted slacken the clamp bolt (B) just enough to allow the body to be turned and rotate it clockwise until the points are clearly closed. Then rotate it slowly and carefully anti-clockwise until the contact points just begin to open. This is best done using a test lamp (connected between the contact breaker terminal on the coil and any convenient earth), which will light up when the contacts open. Verify that the setting is correct by cranking the engine by two full turns up to the points opening indicator and then observing the position of the flywheel "zero" tooth relative to the A/A mark. Then repeat setting process as required. Finally tighten the clamp bolt (B) This timing procedure is fine if the setting is near to correct to start with but if we are dealing with a rebuilt engine or there is any doubt about the correct plug lead connections the following checks may be required.
With the timing set as above establish which of the no’s 2 or 3 cylinders is on the firing stroke. This requires removal of the cam cover to see which of them has slack inlet and exhaust tappets. Or it is possible to set say no. 2 (Lancia’s no. 1!) on compression without removing the cam cover by taking out its spark plug and feeling for the (lack of) compression on the starting handle. Once the cylinder on compression has been identified take off the distributor cap again and verify
that the HT outlet that the rotor is pointing towards has its plug lead going to that cylinder. If you are lucky and you are working with no. 2 cylinder the rotor will be pointing to the distributor HT outlet nearest to that cylinder as per the picture in the handbook. However this is dependent on the engine having been assembled with the gear driving the distributor shaft being suitably synchronised. Often this is not the case! This is only a problem in so far as the final arrangement of the HT leads will not look like the picture in the book!
In any case the final stage is to connect the other three leads working in the sequence of the firing order, i.e. clockwise around the distributor outlets and anti-clockwise around the plug connectors on the engine, to achieve the required 1-3-4-2. What could be simpler!
