Setting the Base Ignition Timing on the

MGB GT By Joseph Legan

Beginning Notes:

The timing cover on both engines does not have the correct timing marks. It is from a

different generation of the engine. The correct timing cover is no longer available

commercially at the time this was written.

This task requires a 5/16” deep socket on a ¼” ratchet, a 7/16” combination wrench, the

jumper battery and a timing light with an advance adjustment feature, and a minimum

of 2 people.

Follow all lab safety rules at all times.

The car in its current configuration had a tendency to shock the individual making the

distributor adjustments if the engine was running. For this reason the procedures listed

within should be followed carefully.

Read all the directions before any work is started.

Tools Required:

All the tools required to do these

procedures. The gloves are

recommended due to the

proximity of ones hands to the hot

engine.

Step 1 Hook up timing light to car and battery

Move the car outside. Place the battery cable clamps on their respective battery posts and

place the spark sensor on the #1 cylinder spark plug wire close to the spark plug itself. Be

careful routing the sensor cables to keep them away from the alternator fan.

Pictures shows the correct

way to hook up the timing

light to the battery and to the

#1 cylinder spark plug wire.

Step 2 Start engine and build heat

Start and run the engine until the water temperature reaches 180 degrees Fahrenheit. A sure

way to make sure the engine is warm enough is to adjust idle ignition timing is to run the

engine until the radiator cooling fan turns on and back off. This will ensure that engine will idle

properly and the adjustments will be accurate.

Make sure water temp is at

180 as indicated by the water

temp gauge before any timing

adjustments are made.

Step 3 Measure and record current timing

This is where the advance feature of the timing light as well as the incorrect front engine cover

come into play. The Top Dead Center (TDC) marks on the crank damper and the front cover

must be used in conjunction with the advance feature to correctly measure the ignition timing.

Reference the pictures for details on the marks. Read the captions for detailed directions.

TDC on front cover as viewed

from above and in front of car .

TDC on crank damper.

With the engine running at a constant 1500

rpm and idling smoothly adjust the advance

dial until the strobe catches the TDC mark on

the crank matching smartly with the TDC

mark of the front cover as pictured above.

Due to the front cover being incorrect, take

the number of degrees indicated and

subtract 22 to calculate the actual ignition

timing. Example: Indicated 55 – 22 = 33

degrees of advance.

Step 4 Shut off engine and loosen distributor clamp

Using the 5/16” socket on the ¼” ratchet and the 7/16” wrench reach underneath the

distributor to the base and loosen the clamp bolt.

This is the step that was getting people shocked in the past. The cause is thought to be the

loose fit of the distributor cap allowing it to shift and then the hands become the path of least

resistance for the spark energy.

Distributor base clamp bolt. Best accessed by reaching under

the distributor. Use caution due to the heat of the engine.

Step 5 Make adjustment by rotating the distributor

Note that the engine rotates clockwise when viewed from the front of the car and that the

distributor rotates anti-clockwise when viewed from the passenger side of the car.

To advance the timing rotate the distributor clockwise.

To retard the timing rotate the distributor ant-clockwise.

Make small adjustments as it is easy to move too far and miss the desired mark.

Step 6 Start engine and measure timing again

Repeat Steps 5 and 6 until the desired setting is achieved.

Note: The current engine as of 2014 made the most power with the timing set at 31 degrees of

advance while the cam was installed per the cam sheet specs.

Step 7 Turn engine off and tighten clamp

With the engine off tighten the distributor base clamp and put away tools.