between piston travel and crankshaft movement for engines of different strokes very clearly. The armature is uncovered by removing the flat casing cover lying between the horseshoe magnets, this often carrying the safety spark gap, and normally serving as a lid. If earlier timing be desired for any special purpose the gap may be widened a trifle, if it be thought the timing is too

far advanced, the gap may be lessened. The contact breaker is fully advanced at this time and the contact points are just about to separate. Having placed everything in position as described, tighten the coupling on the taper shaft and ream out for a small taper pin.

The connections to the various cylinders must be made in the order they fire (see following tabulation). When the cover to the distributor is off, see at which segment the brush is contacting.

Fig. 135.-Simplified Diagram Explaining Method of Timing Magneto

Ignition System.

The wire to the spark plug in the first cylinder is then led to the terminal corresponding to this segment. Then the plug in the cylinder that is next to fire is coupled to the next segment, and so on. The numbers on the distributor show the order in which the various contacts are brought in contact with the rotating distributing brush, and not that in which the cylinders fire. In the sketch the cylinders fire 1-2-4-3. Therefore, the segment num

3 32 4 4 5 5 6 61⁄2 7 72 8

Stroke in inches.

Fig. 136.-Bosch Chart for Determining Advance with Various Piston

Strokes.

ber 3 is coupled to the plug in cylinder 4, and the segment 4 is connected to the plug in cylinder 3, which is thus the last to fire if the explosion takes place first in cylinder 1. The direction of

Advance in degrees.

the distributor brush rotation, if driven by the usual form of gearing, is opposite to that of the magneto armature. Obviously, if one cylinder is timed correctly, the remaining members will also fire at the proper time in the cycle of operations. The positions of the armature, distributing brush, contact breaker cam and

Fig. 137.-Explaining Method of Timing Splitdorf Magneto.

engine piston are easily ascertained by inspection of drawing. The methods of timing Splitdorf magnetos are shown at Fig. 137.

Firing Order of Typical Engines.-The following information relative to timing of leading 1914 and 1915 models of American manufacture will prove of great value to the repairman called upon to repair many different makes of cars. It is well to remember, if the firing order is not known, that it can be easily determined by following the inlet valve movements in the cylinders and noting the order of opening of these members.

ABBOTT-DETROIT.

34-40 AND 44-50-FIRING ORDER 1-3-4-2.

BELLE ISLE FIRING ORDER 1-5-3-6-2-4.

Magneto Setting-Piston dead centre, lever fully retarded. Full advance, spark occurs with crankshaft 13 degrees ahead of dead centre. point gap .018 inch.

Contact

ALLEN.

40-FIRING ORDER 1-2-4-3.

Magneto Setting-Piston top dead centre, lever fully retarded.

AMERICAN.

SCOUT-FIRING ORDER 1-3-4-2.

644, 646 AND 666-FIRING ORDER 1-5-3-6-2-4.

Magneto Setting-Three-quarter inch after dead centre on flywheel.

ARBENZ.

FIRING ORDER 1-3-4-2.

Magneto Setting-Piston .03125 inch late, lever fully retarded.

AUBURN.

4-40 AND 4-41-FIRING ORDER 1-3-4-2.

Magneto Setting-Piston .03125 inch late, lever fully retarded. 6-46 AND 6-45-FIRING ORDER 1-4-2-6–3–5.

Magneto Setting-Piston top dead centre, lever fully retarded.

BUICK.

B 24, 25, 36, 37 AND 38-FIRING ORDER 1-3-4-2.

Delco-With timer cam fully retarded, spark occurs 40 degrees past upper dead centre on firing stroke. With hand spark lever half-way advanced, spark occurs at approximately top dead centre.

B 55-FIRING ORDER 1-4-2-6-3-5.

Delco-Piston dead centre with timer fully retarded.