Warning about distributor rotor arms

[Cameron in UK]

This problem is well known here in the UK but not so much in the US so thought it worth a warning. It affects most small engined British cars and of course Amphicar, and I know Dave the Wave experienced it recently !

There are a lot of poor quality rotor arms on the market, mostly made in China, these WILL fail without warning, normally in the first year of use. They fail by earthing the spark through the distributor so the car just stops and if you aren't aware it takes an age to discover what the problem is.

The original rotor arms from the 1960s are fine. Also new production made of red instead of black plastic are fine. The problem ones were made about 10 years ago but are still be sold today. Sometimes they are in green Lucas boxes, sometimes not. Some of the faulty ones even have a white Lucas stamp on them They are the smaller size of rotor and the thing to look for is a rivet on the top. There is a good picture on this page.
http://www.mmoc.org.uk/viewtopic.php?f=11&t=54989&start=0
Do not use this type of rotor arm or it's almost certain your engine will die at some point.
I've been told that some new production rotor arms of the same shape in black and without the rivet can also fail but haven't seen that, best advice though is only use red rotor arms, they are available in the US from British car specialists.
More info here
http://www.jaguardriverforums.co.uk/showthread.php?t=105
and here
http://www.distributordoctor.com/rotor_arms.html

 

[amphi-Ben]

I will check mine, thx for the info.

 

[Cameron in UK]

Another picture of the junk rotor arms, some have Lucas branding, some not, all of this new production with a rivet is suspect and should not be used.
See links above for more info.

 

[CapnJohn]

Is it the rivet that is the problem?

 

[Cameron in UK]

Mostly yes, the rivet is longer in the rubbish repro ones but also the plastic isn't as good quality, that causes the HT electricity to find it's way down the rivet, through the plastic and on to the little metal clip that keeps it attached to the top of the distributor shaft, you then get an invisible short and the engine stops or runs erratically.
Here in the UK where a lot of cars use this part (Lucas part number DRB101) the problem is well known and I don't think anyone is selling this rubbish any more so it's disappointing to see it for sale in the US as a part suitable for Amphicar.