Repair 7

How to Time a SB Chevy

An internal combustion engine needs four essential things to run. They are: air, fuel, compression and spark. Those four things must work together in perfect harmony or timing. When timing a small block Chevy, we really just change the specific time at which the spark plug will create a spark and cause an explosion in reference to the position of the piston when it is near top dead center in the cylinder.

Instructions

1

Grind the electrode off the bottom of an old spark plug, dont damage the threads. Place the spark plug in a vise and hammer a punch through the spark plug to remove the porcelain. Cut the head off a 3/8 inch by 2-inch bolt with a hack saw. Grind the bolts shaft round and smooth where the head was removed. Insert the bolt into the spark plug so the rounded shaft protrudes out of the threaded end of the now hollow spark plug about 1 1/2 inches. Weld the bolt to the spark plug on the opposite side of the threads. Allow this plug stop to cool.

2

Remove the negative battery terminal from the battery of the vehicle. Remove all the spark plugs from the small block Chevy engine. Label the spark plug wires to keep them in order for easy replacement.

3

Clean the harmonic balancer so the zero degree line can be seen. Use a wire brush if needed. Insert the special modified spark plug into the number one cylinder of the engine. The number one cylinder is the cylinder closest to the radiator on the drivers side of the vehicle.

4

Rotate the engine very slowly and gently by hand until the piston comes up softly against the plug stop. Make a prick punch mark that aligns perfectly with the zero mark on the timing tab. Rotate the engine in the opposite direction very slowly and gently by hand until the piston comes up softly against the plug stop. Again make a prick punch mark that aligns perfectly with the zero mark on the timing tab. Immediately remove the plug stop.

5

Measure the exact distance between the two prick punch marks and divide that measurement by two. The true top dead center is exactly half the distance between the two punch marks and there should be a line labeled with zero degrees on the balancer, if the balancer is not damaged. If the original zero line does not fall exactly halfway between the punch marks, scribe a new line using a hacksaw blade. Use this new and precise line to time the engine.

6

Reinstall all the spark plugs and reattach all the spark plug wires. Reattach the negative battery terminal to the battery. Slightly loosen the distributor hold-down bolt located at the base of the distributor shaft. Remove the vacuum line from the distributors vacuum advance and plug the line with a small bolt.

7

Set the knob on the timing light to the desired timing degrees according to the specifications for the vehicle. Also, adjust the engines idle speed to the desired specifications for the vehicle, using the digital readout on the timing light. Clamp the timing lights pickup clamp to the number one spark plug wire. Clamp the red power clamp to the positive terminal of the battery and the black ground clamp to the negative terminal.

8

Start the vehicle. Aim the timing light at the harmonic balancer. With the engine running, align the top dead center mark on the balancer with the corresponding mark on the timing tab. Rotate the distributor in one direction or the other to align the marks as needed. Tighten the distributor hold-down bolt when the marks align perfectly. Recheck the timing to be sure it did not move while tightening the distributor. If it moved, repeat the timing procedure until the marks align and the distributor is tight.

9

Reset the idle speed and remove the timing light. Reconnect the vacuum line to the distributor the timing should be set.