Morris Minor Owners Club

Hello people,

Long time since I posted here, I am helping someone service a 1963 2 door saloon with a 948cc engine. We ordered a service kit, but it appears the rotor arm is an unusual type, so the standard rotor arm does not physically fit on the distributor.

The current arm (which works fine) is on the left, and the new one is on the right. The inside diameter is maybe 2mm smaller on the new arm, so it will not fit onto the distributor spindle. Any thoughts?

Just keep using the old one !

Not a bad idea of course! However the owner is planning to sell the car soon and wants to advertise it having just had a good service. Given the likely cost of the rotor arm and time to install it I think its worth doing!

Give it a rub with abrasive paper - then it's had a 'good' service, rather than fitting a crappy sub-standard arm!! You sure it's not the 'key' on the new arm that's stopping it going on -it looks quite large....

I found that ESM sell a red performance rotor arm that looks like it is the same as the old one, although it is supposed to be for the same distributor. I wonder if the new rotor arm I bought is a bit poor on the quality control in terms of dimensions.

Does the long contact arm affect the timing, ie do the points open earlier?

My understanding of the distributor is that the cam on the spindle determines at what point in time the contacts touch and the spark jumps, the arm needs to be in contact with the correct spark plug metal terminal, but how far along the arm it happens to be is not too important.

If the arm was not in contact at all, then the spark would reach the rotor arm, but not be able to get to the metal terminal for the spark plug.

I came to this realization when trying to adjust the timing of an MPI mini at the side of the road by rotating the distributor body, the timing was not effected at all, unless you rotate it so much that the arm is not in contact with the metal terminal when the spark is supposed to fire, and then the engine quickly dies. The MPI minis I believe trigger the "points" electronically based on the position of the crank sensor.

Hahahahaha - I suspect it was an SPi - and yes, no points..... The MPi doesn't have a dizzy.......

hello bmcecosse, with your usual attention to detail as always!

Probably an spi then, no carb but definitely a dizzy present. I took pity on someone stuck at the side of the road, opened the bonnet expecting something pretty similar to the morris minor engine and got a bit of a shock! wires everywhere!

Well done for stopping - did you get it going - or offer a tow?

Battery terminal was quite loose, could be easily turned by hand and was quite dirty, I think this was giving intermittent power and causing many of the problems. The wiring was a mess so I decided not to dig a hole and make it worse. Battery terminal bodge sent them on their way but it needed a lot of work!

Well done...most Minis need a 'lot of work'.....

i have found that some of thease red rotor arms have burs inside them give them a rub with scratchy paper and a good punch with the palm of your hand and they go on fine .

And never come off again.....

i should of said clean the burrs off so it fits easier ,