MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - distributor cap

does anyone have a diagram that shows which wires go in which hole of the distributor cap. Don't ask why I need to know? I looked in the book and at Baneys site, no luck

Rissell
R Egge

Have a look at the Moss catalogue diagram:
http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29251
Keith Morris

But which hole is for plug 1, 2,3 and four??
R Egge

It is simple No1 is set by the rotor arm pointing at it when no1 cylinder is on its firing stroke and then looking on top anti clockwise from No1 is 3,4,2
Bob (robert) Chairman north lincs and district pigeon fanciers society

Mr. Egge: looking at the referenced Moss illustration, number 1 is to your right, then numbers 2,3,and 4. Just follow each wire to its respective hole in the cap. Marv Stuart
Marvin Stuart

Just a rambling comment to pass the time.
No Distibutor on any car has a "correct" position, only a "most convenient" position.
I say this because people often say "my vacuum advance unit is facing in a diffficult direction" or something similar.
Assuming that you start with an engine correctly timed. On a four cylinder car if you turn the Distributor 90 degrees in either direction, remove #1 spark plug to feel which stroke is compression, place the #1 plug lead the in Distributor cap hole to which the rotor is pointing, replace the other plug leads in the following holes in the firing order as given in the Workshop Manual, checking also in the Manual which way the rotor turns.
Job completed. In practice, unless you have some method of turning the Distributor exactly 90 degrees, you would have to do the final timing with slight movements of the Distributor.
You can also turn it in either direction in any increments of 90 degrees (90, 180, 270) and for six cylinders 60, 120, 180, 240, 300 and for eight cylinders 45, 90 etc.........

Mick
Mick Anderson

Mick is right that any distributor will work in almost any position if you shuffle the wires around to suit. However, there is a standard configuration for the MGA, and mechanics in general will have an easier time getting it right with the least labor time if you adhere to the standard setup.

Follow the Book carefully, and try not to be confused by things like "Larger offset upward", and exhaust stroke vs compression stroke. When the distributor drive gear is installed in the correct orientation, and #1 piston is at Top Dead Center on compression stroke (both valves closed), the rotor will point in the general direction of #1 spark plug. If it doesn't, and you want it to, then you need to reposition the distributor drive gear.

Next, the traditional (factory) orientation for the distributor has the vacuum unit pointing roughly straight up, or just slightly clockwise from straight up. Position crankshaft at TDC, or 7d BTDC by the book. Rotate dizzy body anti-clockwise to close contact points. Then rotate dizzy body slowly clockwise until the points just start to open. Lock it in that position.

Note that the rotor is still pointing at #1 spark plug. The terminal position in the dizzy cap at that position will be for #1 plug wire. For a top entry cap it will be the terminal post closest to #1 spark plug. Going anti-clockwise around the cap follows with wires for 1-3-4-2.

For the (original type) side entry cap (see attached picture), the same applies to everything up to the internal terminal positions, but the wires outside are different. When the dizzy drive gear and dizzy body are properly oriented, the wires emerge from the cap pointing upward or slightly clockwise, same as the vacuum unit. The center most wire is the lead from the ignition coil. The other HT wires are on two levels, upper and lower. The lower level wire closest to #1 spark plug is for #1 plug connection. Then looking down at the wire side of the cap, wire connections are in the same sequence, anti-clockwise 1-3-4-2. That is, the second low-level wire (away from #1 plug) goes to #3 plug, the wire above #3 goes to #4 plug, and the wire above #1 goes to #2 plug.



Barney Gaylord

I would go along with Barney's explanation in the last paragraph as to the way the distributors were set up on the production line. His attached picture appears to be supported by the image of the 1600 engine bay in my flame trap post. My picture is not too clear, however, the 1 and 2 wires both appear to go to the same side of the cap as shown in Barney's photo.

Steve
Steve Gyles

This thread was discussed between 10/10/2007 and 11/10/2007

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.