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MG TD TF 1500 - rev-limiting rotor button

Hi Guys,

I am looking for a rev limiting rotor button to fit the standard XPAG distributor. It would need to be set at about 7000 RPM to suit the race TC. Does anyone know where I could source one? Are they very reliable? It is something I should have done 45 years ago although I have been lucky so far. I could perhaps modify one made for a different dizzy? Think I might need to protect the engine from driver errors caused by old age!

Bob Schapel
R L Schapel

Bob do your class rules limit what you can use? Electronic rev limiters? Magneto vs external coil ? Points vs EI ?
W. A. Chasser

I think electronic rev limiters are allowed but I still want to stay with something simple (to match the driver). I use a conventional coil and points as electronic dizzy mods are illegal. The conventional system works perfectly well anyway.

Bob
R L Schapel

This is what I came up with, most are Bosch 009 perhaps they might fit a Lucas distributor???
(Google RPM limiting distributor rotors)
https://www.google.com/?gws_rd=ssl#q=rpm+limiting+distributor+rotors

Len Fanelli

Lotus used Lucas rev-limiting rotors for a number of years on the Europa and Elan models. Might want to ring up a couple of Lotus spares suppliers to see what they have... should fit your dizzy.
Kevin McLemore

Bob,

You can find all the info on the Lucas part numbers, here.

http://mgaguru.com/mgtech/ignition/ig111a.htm

John
J Scragg

Thanks Len, John and Kevin, Good suggestions.

Yes, I have googled "rev limiter rotor buttons". The 009 is a good possibility. I don't know yet if it will need some modification. I should be able to see one at a VW shop. The Lucas is perhaps more likely to fit straight on, but less likely to be easily found. I will let you know what transpires

Bob.
R L Schapel

Just for my interest to see what they look like, I looked up Lucas rev limiting rotor on Ebay UK and here is one to view but it is for a Jaguar 6 cylinder. Ebay item number
331907739473
and another one indicated for a 2.6 liter Land Rover: 201619711280

I do recall that the Ford based twin cam 1600cc Lotus engine used them as well.
John Quilter

7,000 rpm is right around where standard lucas rotors start cutting out.
D mckellar

The "Distributor Doctor" in Somerset UK replied to my enquiry. He said the rev-limiter rotors which suit (such cars as MGTC) were made for cars such as the twin cam Lotus but were "wildly inaccurate and unreliable." Most are also suited to bigger (e.g. Jag) dizzys or have the wrong cut-out limit. He suggested an Armtech or similar electronic device. They are about 108 UK pounds and are probably the logical option but I do want to stay simple "low tech".

I would think the Bosch unit would be more reliable and I know they are more available in a range of rev limits. I bought a s/h 009 (6500rpm) rotor to study but I will have to do more fiddling to try and make it fit. The shaft diameter is perfect but it would need trimming off at the bottom to bring the rotor down so the locating key engages in the cam keyway. (Very do-able I think.) The vertical thickness is then about 3mm to much but I think a cap could be modified to fit that too. The biggest problem is that the sweep diameter is about 8mm too big. It might be possible to fix this too with a bit off the rotor and a bit more off the cap posts.

If I have any success with this mod I will post the details but it might not be for a while due to other jobs/commitments.
Bob
R L Schapel

This thread was discussed between 13/07/2016 and 18/07/2016

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