Why is nothing ever straight forward

[pgp001]

So having already done a trial assembly of most of the main parts of my spare engine, I have come to the point where the back plate needs to go back on. The only trouble is it does not fit anymore.

Now the new oil pump is in place the big hole in the plate and the tin cover is fouling the oil pump body. It looks like the hole in the plate is machined nearly 1/8" too low down.
The old pump had a much smaller body when I investigated, so the problem was not apparent on initial strip down, now this pump is a completely different shape an catches at two points in the upper part of the hole.



I am not 100% sure what to do about this, I could re-machine the hole on my milling machine, but that would leave very little wiggle room for the tin cover to seal. Or I could try and find a different pump with a smaller body as per the old one I took out. I dont really fancy removing metal from the pump itself.

The last option would be to try and get hold of another back plate I suppose.

All suggestions will be considered.

Phil

[liammonty]

I had the same problem when I rebuilt my engine - the pump I fitted was supplied by Swiftune and of good quality. I wasn’t keen on modifying the pump housing either but had read of others who had done it with success, so I went ahead. 10 years on all is well. Surely changing the back plate won’t cure the problem, unless you modified it?

[philthehill]

I suspect that you are trying to use a 1098cc rear engine plate.

There is a considerable difference between the 1098cc rear engine plate and the 1275cc rear engine plate as regards the oil pump aperture.

They are not positioned/centred the same. You have to use the right rear engine plate. The 1275cc rear engine plate is on top in the pictures below.

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The oil pump covers are also of a different size to take account of the different size bodies of the oil pumps.

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[pgp001]

Hi Phil

Mine is a 1098, and has the Mowog tin cover.
Having spent last evening trawling through the forum, it seems I am not the first person to encounter this problem when fitting a later design pump.
It seems very strange that the hole in the plate is not concentric with the one in the block, I had assumed that mine was a rogue that had slipped through, but now I am thinking they are all going to be the same.
So the plan is to buy a different pump with a smaller body as it had fitted originally, I just havn't decided which one yet.
ESM do one that looks like it will physically fit, do you reckon that is as good as it gets ?

https://www.morrisminorspares.com/engin ... it-p830266

They even mention in the description that it requires "No Modifications" to fit, I had wondered about that statement and now I know why.

Phil

[philthehill]

Personally I would obtain a 1275cc rear engine plate and oil pump cover and retain the oil pump you have.

The modification usually refers to the need with some pumps to drill and tap additional holes on the block to secure the oil pump. Some oil pumps have between two and four securing bolts.

Below is a 1275cc Cooper S pump I fitted to my Minor way back before the 1275cc Midget/Sprite rear engine plate and oil pump cover was available. I had to modify the pump body to suit the 948cc block and dome the oil pump tin cover. So been there and done that - videos were not available back then.
I have measured a selection of 'A' Series oil pumps to determine the max diameter of the pump face that goes against the block including one that is the same as pictured in your original post to this thread and they all measure 90.3mm O.D. The variable is in the depth and shape of the pump body which will interfere with the small block tin pump cover.

100_2020.JPG (261.01 KiB) Viewed 682 times

As regards oil pumps have a read of this before you decide on which pump to use:-

https://www.calverst.com/technical-info ... oil-pumps/