Morris Minor Owners Club

Hi all,
Can I use the 1098 distributor in my 1275 midget engine which I am quite near to fitting,(25D stamped on distributor)
Also can I dispense with the bypass hose?
Many thanks,
Martin.

Yes (but probably not the ideal advance curve) and yes. Drill a couple of 1/8" holes in the thermostat rim to compensate for the hose.

The Lucas 25D4 distributer was fitted to the 1275cc Sprite Mk4 & Midget Mk3. The same as fitted to the Minor 1098cc engine.
The Minor timing is set static at 3 degrees before TDC whereas when fitted to the MG Midget engine is set static to 7 degrees before TDC but the timing will have to be re-determined to suit the new engine configuration though the above figures are a good starting point.
Some MG Midgets were fitted with the 23D4 distributer but that did not have the vacuum advance unit fitted.

The by-pass hose can be dispensed with but make sure that you get the right blanking plug. The thread is 5/8" x 16 TPI Unified National Special (UNS). A 5/8" x 18 TPI UNF blanking plug will not fit properly.
If you decide to replace the cylinder head by-pass stub Mini Sport of Padiham can supply the correct thread stub.
https://www.minisport.com/12a2075-cylin ... e-kit.html
You will also need to blank off the water pump stub or fit a water pump without the by-pass hose facility.
http://www.minispares.com/product/Class ... ssic/water pump.aspx|Back to search
Phil

Why would you wish to dispense with the bypass hose? Does it not serve some useful function?

The bypass hose allows some water to circulate through the head before the thermostat opens so alleviating any hot spots in the cylinder head during engine warm up.
That is why the recommendation is to drill some holes in the thermostat to allow some limited circulation if the by-pass facility is removed.
There is no requirement in normal use to remove the by-pass facility but once removed it is one less area where water can leak.
Provided that a good quality by-pass hose is fitted and the cylinder head stub is in good condition I would leave in place.
Later heads did away with the bypass facility but they still had water circulating through the cooling system via I believe the heater system.
Phil.

It makes for much better heater operation in winter - and as above - removes a source of possible engine disaster if it bursts.