mk11 distributor.

[bob cottam]

Hi All, anyone know anything about the late mk 11 distributor- mine appears to be off a 1946 Austin 10hp car!! It needs work, of course, not least the shaft is worn, more so than the bushes, but before I set off on a quest for a new shaft-I don`t know for sure if I have the right one to begin with.It is stamped 15 degrees on the underside of the advance weight carrying plate-is this the right one ??? Cheers, Bob.

[brenton.roy]

Bob, do you still need an answer? I have one in a box somewhere.

[david.anderson]

Bob
the correct distributor for a square 4 is a Lucas DKX4a. As far as I know that distributor was used exclusively on the square 4. There were other similar distributors that were used on Austin and Morris vehicles including possibly early Morris minor. The body appears to be the same with a spare distributor that I have (from I was told an early Morris Minor) however the shaft/points cam and rotor is different. the shaft is also designed to run in the opposite direction.
Any 4 cylinder distributor that can be adapted to fit will run. It is just a matter of setting the overall advance and the advance curve right. (Something which Lucas never seemed to manage with any distributor).
From memory 15 degrees is right (which is actually 30 degrees total advance as the distributor is running at half engine speed).
David

[bob cottam]

Thanks for the replies-any info to confirm that I have the correct innards will help. The cam, bob weights and toggles must be right(anti-clock bob weights) All I know is the Lucas parts book quotes "range" as 14-16 degrees which I suppose would tie in with the 15 deg. stamped on the underside of the action plate on the shaft. The correct Lucas number for the shaft is 420691, but this is not stamped anywhere so i don`t know for sure. Regards, Bob.

[david.anderson]

Bob
the attached photos show the point cam and rotor in my square 4. My other distributor (possible Morris minor) has a much larger point cam with more rounded corners. sorry about the green tape but the condenser is isolated from the distributor as I am using the points to trigger a Ford TFI unit which I have mounted under the seat. the condenser is only there as a back up should the TFI ever fail. The distributor should look like the photos without the green tape.
David

[markus.nikot]

Did Lucas supply any list with an advance curve. Means the adjustment in degrees per rpm.
Reason of this question, a friend got a tester and i have now the chance testing my SQ4 distributors.

Markus

[david.anderson]

Markus
distributor advance curve details would be good to know, but did Lucas get the advance right originally. They certanly did not with most notably MGs.
More recently the change to unleaded fuels has created problems for higher compression engines fitted with Lucas distributors. Most MG owners have had their advance curve remapped to prevent incessant pinking. Generally the advance curve is slowed so that full advance does not occur until much higher revs are achieved. While our low compression square 4s have not had pinking problems it is probably reasonable to assume that a stretched advance curve may also be beneficial.
David

[Eero.Korhonen]

Hi,
Cars have vacuum operater advance unit to give more advance in acceleration.
Motorcycles don't have this. Is this distributor immovable in mk11?
Some bikes have some movement to get enough advance in riding position.
Br, Eero

[markus.nikot]

David,
this could be an explanation for pinking the in my Triumph TR6. The curve - tested on the car seems ok but on some occasions i hear a pinking. Compression is standard only the fuel is new.....

Eero,
my Triumph don't has a vaccum advanve or retard it works only with the bobweights like the Squares.
It is correct for the 71 carb TR6.

Markus

[david.anderson]

Markus
here in Australia this firm has a good reputation for remapping distributors. http://www.performanceignition.com.au/i ... erformance
they remapped a friends MG Lucas distributor and it was a different car afterwards. Here are the before and after advance figures. Apart from slowing the rate of advance it looks like they also reduced the total amount of advance.
Before Retiming. After Retiming.
Total advance with 6* static. Total advance with 10* static.
250 RPM 6* No advance below 1,000 RPM.
600 RPM 12* 1,000 RPM 10*
2,000 RPM 26* 2,000 RPM 18*
3,200 RPM 34* 3,000 RPM 26*
4.000 RPM 34* 4,000 RPM 32*
Vacuum Advance 12* Vacuum Advance 18*
the over advance at 3000rpm was the cause of major pinking.
David