[pre-xk] Lucas 407030 Rotor Arm Breakdown

Hi folks, 3 1/2 Mark V with Lucas DVXH.6A stock distributor got
about 200 miles on new old stock Lucas 407030 rotor arm and
then found no-start condition from 5-20 minutes after driving
somewhere and turning engine off. Starter cranked strongly,
ether sprayed into carbs did not initiate any combustion.
Timing light on high voltage feed gave steady strobe signal
when engine was cold or when running smoothly, no-start
conditions gave intermittent strobe.

Pulled distributor cap, inspected cap and plug leads. No
evidence of tracking inside cap. Pulled NOS rotor arm and found
tracking on inside of arm to distributor shaft. Replaced rotor
arm with one of the ‘‘red’’ plastic aftermarket items. Car runs

Apparently at least on this one NOS Lucas rotor arm, when the
rotor gets the heat soak after turning engine off, then
internal tracking can occur, goes away when rotor cooled.

What rotor arms are recommended these days to replace Lucas
407030 ?–
Roger McWilliams
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–


Roger McWilliams wrote:> Replaced rotor

arm with one of the ‘‘red’’ plastic aftermarket items. Car runs

Roger McWilliams
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

I am working on a 1939 SS 100 and need a dist. cap & rotor. The #s on the distributor are:
408669 and DUH6A - 0. There are no #s on the rotor. Searching around this site, I came up with this post.
Any one who can steer me in the right direction, please chime in.

@Ed_Nantes or @Rob_Reilly should be able to help.

Well, I don’t find a reference to 408669, but I did find DUH6A/0 in both the 2.5 and 3.5 Litre saloon parts catalogues. The distributor number given is 406550 for all L and M serial number engines. The 100 supplements refer back to these.
The correct rotor for those is 404923.
The cap (aka cover) is 404520.
Try Alan Gibbins or Worcester Classic Spares.


I’m not sure Worcester would have the DUH6A dist cap. They come up occasionally on ebay. They aren’t cheap generally about AU$ 100. I wass ent aaan auction listing for a NOS DUH6A dis the other day , unsold at about 60-70 GBP.
Although they were made in both ACW and CW rotation. While they can be converted it needs a new shaft as the scroll on the shaft is opposite handed on each. BUt our local dis places puts aBosch shaft and Cam in .
Claims also that the bosch cam has abetter profile than the Lucas. Have a look at my post the other day about earthing issues with the original bakelite base plate that relied on the mounting screw s to earth it. A later replacement plate with an earth terminal is worthwhile using.

Here is a photo of a rotor I have sitting next to Lucas 404923 box. Anybody want the rotor?

Just to be clear, I don’t know if this is a 404923 rotor.

I am interested in it. Also would like a cap too if one can be found.

Hello Robert, send me a mailing address to mcw@uci.edu and I will put the rotor in the mail to you.

Any chance you worked on a Jaguar Mark V for Zach Berkowitz (or Nate) with invoice number 384 and date 12/15/1997, completed 02/09/1998? I bought that car somewhere near year 2000 and have used it ever since.

Well there’s good news , and bad news
There is a NOS cap on on ebay at present
item number 254217910926, buy it now. only GBP 179.99.
Yes , expensive but these days a really good 3 1/2 SS100 is bringing $ 1 million,so not over capitalising.
Otherwise just keep looking on ebay uk. I used to pay about AU$ 100. Which is why you buy parts when you can get them ,no wait till you need them.

Works for P6 Rovers, and DKWS, too.