Massive thank you to Phil - and more advice please?

[Mark Wilson]

I've finally got round to tackling my 1275 Midget engine in earnest, and have just finished drilling and tapping for oil gallery blanking plugs by following philthe hill's fantastic guide to this job. I've never done anything quite as near to serious engineering before and have to say his instructions and illustrations are absolutely spot on. This needs to be moved to a sticky somewhere - how about a new section of How To Guides for items like this? It's a lot more than just a Useful Tip!

http://www.mmoc.org.uk/viewtopic.php?f= ... ug#p566082

Just to show Phil how closely I have followed his instructions!


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I have hit one snag, though. I couldn't remove the solid brass plugs by the "tapping and screwing down a nut on a washer" method, as they were just too tight and stripped the tapped threads. So I drilled out the plugs with the tapping drill, which produced a huge amount of swarf which got everywhere despite my vacuum cleaner next to the drill bit. I've been diligently locating and cleaning out all the oilways, but the oilway between the rear main and the distributor side gallery appears to be solidly blocked. I can squirt WD40 through it, so I know it connects, but I can't get even a thin copper wire from one end to the other. I think I need to drill it through, but would like to check that there is no obscure reason that this in fact should have a blockage here. You can see below the approximate position of the blockage at the tip of the drill bit.

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Mark

[Declan_Burns]

Mark,
Here is a very useful link to the topic "oil galleries on BMC A series engines"
http://www.nonlintec.com/sprite/lubrication/
I used a long air blast nozzle to clean out the galleries followed by thin pipe cleaning brushes (8 ... 9mm diameter).
Regards
Declan

[Mark Wilson]

Very useful indeed, thanks. Interestingly he shows the passage from the main gallery to the mains on the photo of the front of the engine, but not the one I'm having trouble with on the photo of the rear. It is there, however, and as it can only have been formed by drilling I think I'm safe clearing it with a drill. I did have trouble removing the final bits of the brass plugs, so I suspect that a largish chunk has become wedged by my efforts with my long brush.

[les]

With some stout wire I wonder if you could feed it in from the oil gallery end, bending and straightening as it goes in. Any obstruction may be better dislodged pushing from this direction? It must be a clear channel as it feeds a bearing. It may be possible to tap anything out using a good fitting bar, can't see there being any too tightly packed obstruction.

[Dean]

Well done, a nice bit of toolmaking being done there (I am a toolmaker by trade ).

Don't be tempted to use a drill if you want to tap something out. It may break and embed into cast.

Also, cast tends to just cut into dust, so I'd be surprised if it's anything you may have done. The obstruction may have already been there.

Good luck stay patient, I'm sure it'll come free eventually.

[Mark Wilson]

I tried everything, but in the end had to resort to drilling. The obstruction was ferrous, and was solid - and couldn't have resulted from my removal of the brass plug. I don't know the history of this engine and I've never run it, but whatever was there must have prevented proper lubrication of the rear mains, which may account for the mains being ground to -30 and the shells being scored (unfortunately, as they were being replaced I don't know which were the rears).

I do have a theory as to what has happened - it's a bit extreme, but I'd be interested in anyone's views. The cylinders have been lined and the bores are +30, with little wear when I bought it. The oilway obstruction is very close to the cylinder wall. Could the lining have resulted from a rebore breaking into the oilway, and then being carelessly welded prior to sleeving? Even after drilling through there is still a rough patch on the wall of the oilway.

I've dismissed my first theory - someone getting so frustrated with the crankshaft scroll dripping that they plugged the bearing's oil supply!☺

[Mark Wilson]

Well done, a nice bit of toolmaking being done there (I am a toolmaker by trade ).
.

Thanks, my father worked in what used to be called Jig and Tool (before it became Production Engineering) so I wish he could have seen my improvisation!

[philthehill]

I am glad that you found my post useful.

Can you please post the current depth of the hole from the rear main shell bearing seat and does it now connect with the R/H (O/S) fore and aft oil gallery?

Phil

[Mark Wilson]

92mm, is full depth from face of bearing bed to wall of main gallery, just beyond the end of the thread for the blanking plug.

[philthehill]

Mark
Many thanks for the reply.
The reason I asked was that I have checked my two spare blocks - one 1275cc 'A' Plus and one 1275cc Midget to see if the drilling is direct from the bearing seat to the main gallery.
Neither is direct but there is flow between the main gallery and the rear mains.
A drill inserted into the gallery from the bearing seat will only go in 65mm approx.
I know the history of both blocks so nothing untoward has been done to either block.
Whilst I am struggling to find any information re the flow/quantity of oil directed to the rear main bearing I have it in the back of my mind that the drilling was restricted to limit the amount of oil going to the rear main bearing because the scroll could be overwhelmed if too much oil was sent to the bearing.
(anyone out there with additional information re the restriction to enlarge the discussion)
The 1275cc Midget engine was used in my comp Minor and there was never any problem with oil flow to the rear main or the longevity of the rear main bearings.
If the restriction required was as I thought and you have removed it - no problem - a suitable grub screw with a hole drilled down its centre can be fitted at the main bearing end of the gallery. I have similar fitted into my comp crankshaft.
Phil

[les]

That's interestingly, it appears I wrongly thought the channel would be a direct oil feed from the gallery, Phils thoughts on this seem realistic. The drilling sequence on the block seems quite complex. Disregard my previous post on this!!

[philthehill]

Les
Both the front main and centre main are directly served from the O/S oil gallery without any restriction.
The link from the oil gallery to the rear main is complicated. I can put compressed air from the outlet in the rear main bearing seat to the gallery and the flow of air is good but not as good as that from the front and centre main bearing seat back to the oil gallery.
I will take the O/S oil gallery blanking plugs out of the 1275cc Midget engine and see if I can identify the route and if there are indeed any ex works restrictions in place.

Mark
Can you please check the oil pressure relief valve seat on your engine as the oil gallery in question - if drilling is continued from the rear main bearing seat - would appear to intersect in the area of the oil pressure relief valve seat
Phil

[Mark Wilson]

Oh dear, I seem to have been a bit impatient in drilling it clear. Two thin brushes show that the relief valve oilway does intersect with the rear main bearing oilway and then on to the pump. Why would the restriction have been placed at the intersection, which must have been difficult to engineer? Was it blocking or limiting the relief valve oilway as well? The grubscrew solution sounds feasible if there is no requirement to limit the relief valve oilway.

Don't really want to take the engine out more times than necessary, but do you think there is any merit in trying it with the rear mains oilway unrestricted? I do intend being very careful with setting up the scroll clearances and with the crankcase pressure.

Many thanks for taking so much trouble

Mark

[Mark Wilson]

After a bit more research I now know that the "obstruction" I drilled through was in fact the oil pressure relief valve seat, which you see in the middle of the fascinating illustration below. Pity I didn't find it before doing the damage....

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Apparently some oil does pass around the centre of the valve seating to reach the rear mains. A new seat is apparently available and providing I can manage to extract the remains of the old one the damage should be repairable. I would be grateful for advice on this procedure from anyone who has tackled it. UPDATE - these are apparently out of stock everywhere. If anyone has one, or knows where to find one, please let me know.

Please don't anyone feel guilty about leading me into this act of vandalism. In my impatience I drilled it out before reading anybody's advice about clearing the oilway - so much for feeling pleased with my engineering prowess!

[les]

A great example of-----' a picture paints a thousand words'

[amgrave]

I did wonder myself if the oilway was deliberately restricted so as not to overwhelm the scroll but on the other hand if the rear bearing is new the amount of oil it will pass would be small, it might become more of a problem once the rear bearing becomes worn and so more oil will pass. It would make a good worn bearing indicator I should think

[philthehill]

Mark
Well done for finding that sectioned block - it clearly shows what is required.

This is a link to the part you want Pt No: 2A797 - unfortunately sold out but it may jog a few memories.

http://www.somerfordmini.co.uk/eshop/in ... ts_id=6783

Phil

[panky]

Not sure if this is the same size.

http://www.minispares.com/product/Class ... o%20search

[panky]

Have you actually broken through into the centre of the seat

[les]

Taking one from a scrap block might be the only supply, if it can be removed without damage. Perhaps experiment with the damaged one, maybe by tapping a few threads into it, and pulling ?------ using a 1st tap (tapered)