play in distributor shaft

for those with Series MM sidevalve cars produced between September 1948 and February 1953
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ian.mcdougall
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play in distributor shaft

Post by ian.mcdougall »

I was checking timing on my series MM and checked to see if automatic advance and retard were free . I found a lot of rotary free play in the distributor shaft without the automatic advance and retard rotary movement there was almost the same amount of movement . if you turn engine to TDC the points are open but if you turn shaft without activating the advance and retard it closes the points so timing could be well out. Is it supposed to be like this if not can it be fixed . I hope I have explained it properly
Thanks

philthehill
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Re: play in distributor shaft

Post by philthehill »

There should be no obvious play between the distributer drive shaft gear teeth and the gear teeth on the camshaft.
The the distributer drive shaft gear teeth are prone to wear especially after a prolonged usage.
I have seen drive shafts were the teeth have been worn half away which lead to ignition timing floatation of several degrees..
The only solution is to replace the distributer drive shaft with either a new shaft or a good used item.
https://www.moss-europe.co.uk/spindle-d ... soc=137991
https://www.ebay.co.uk/itm/185459778741 ... Swe7ZioyTD
Take care not to drop the drive shaft into the sump when removing and refitting the drive shaft. Use a long stud screwed into the top end of the drive shaft to facilitate removal and installation.

ian.mcdougall
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Re: play in distributor shaft

Post by ian.mcdougall »

Thanks for reply
Mine is sidevalve engine which without looking at the manual means the oil pump is driven off the shaft I think . I stand to be corrected

philthehill
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Re: play in distributor shaft

Post by philthehill »

The side valve engine distributer drive shaft is driven off the cam shaft in the same way as the later OHV engines.
The main difference is that the MM drive shaft is comprised of multiple parts,
1. shaft and gear - pump drive.
2. bush - shaft gear.
3. connector shaft and gear.
4. shaft distributer drive.
5. sleeve - distributer drive.
There are two pins holding the shaft assys together.
The oil pump is driven off the bottom of the shaft and gear - pump drive by a flat drive on the bottom of the distributer drive shaft.
If the two pins are not worn the same conclusion may be applied as to the OHV distributer drive in that the drive gears on the shaft are worn.
It is worth checking the condition of the distributer shaft flat drives both male and female parts.
There are good working illustrations in the BMC wksp manual of how the distributer/oil pump drive is assembled and works.

ian.mcdougall
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Re: play in distributor shaft

Post by ian.mcdougall »

So I took the distributor out , using a screwdriver in the offset dog on the shaft there was still free play got a magnet and pulled the shaft out and using said screwdriver checked what I assume is the piece that is driven by the camshaft and there was a lot less free play . I found a piece of very thin almost like feeler gauge thick steel and made a u shaped piece for the fork on the end of the shaft reassembled and there was a very marked improvement in the free play so will see how long it lasts until it comes back.

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