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+--- Thread: Pressure relief ball (/showthread.php?tid=8497)
RE: Pressure relief ball - Chris KC - 18-04-2023
My gauge pipe came adrift on holiday last summer (it was poorly soldered and I'd just completed a jaw-breaking stretch of cobbles) and all but emptied the sump over 1/2 mile while I was busy looking for a campsite. I'm pretty sure the resulting slick was visible from outer space. My engine (n.b. pressure fed crank, but with over-bored A7 pump) kept trickling along at about 30 mph without harm, which is comforting to know.
RE: Pressure relief ball - Steve kay - 18-04-2023
Torches, magnifying glasses, drawings in Woodrow, encouragement from the forum.......and yes, one of the two blanking plugs in the crankcase on either side of the oil pump is missing. Naturally the inaccessible plug. Quick straight to the phone and have the benefit of Mr Cochrane. David's memory is remarkable, he was able to immediately identify them as 1/8" BSPT. Particularly impressive as he gets asked for them about once every five years, so certainly has none in stock. So the next question, any suggestions as to where 1/8" BSP tapered thread plugs might be purchased? My initial computer searching has not come up with a source immediately.
RE: Pressure relief ball - Jeff Taylor - 18-04-2023
Having never taken these plugs out I'm not entirely certain what they look like. Are these any good?
https://shop4fasteners.co.uk/bspt-taper-pressure-plugs-self-colour-1-8.html
RE: Pressure relief ball - Steve Jones - 18-04-2023
Put 1/8" BSPT blanking plug into Google and it comes up with a multitude of options (£1.02 inc VAT at Bearing Boys for instance). However, most towns have a hydraulics supplier who should be able to supply although it's likely to have an allen key hex rather than a screwdriver slot.
Steve
RE: Pressure relief ball - Reckless Rat - 18-04-2023
Anyone with a scrap crankcase should be able to help you out with one. Thing is, where did it go? is it still in the sump, or lodged in a corner somewhere in a pile of crud?
RE: Pressure relief ball - Chris KC - 18-04-2023
Yay! A result.
Steve, these plugs are usually exceedingly difficult to remove, they were punch-locked around the diameter in the works and even if that is ground back they will still put up a fight. By which I mean to explain that if one has come out, it is probably because someone previously removed it, possibly damaged the thread, and the new plug for one reason or another was not a proper fit. With this in mind check that your new plug fits well, clean the threads with solvent and use some suitable Loctite on it. If necessary tap slightly oversize to repair the thread.
I'm pretty sure the hole in the case is BSPP, you can use a BSPT plug or BSPP if it is sealed (preferably with a flange). Doesn't really matter as long as it does up tight. Any old-school plumber's merchant should be able to help you out. Be wary of stuff from China which is usually not BSP at all but NPT, which is 'similar'.
RE: Pressure relief ball - Ruairidh Dunford - 18-04-2023
Good that you found the cause and I must say, you are lucky to have escaped damage on your road trial.
I have a box of these, if you are unable to source. I use hex drive ones which mean you should be able to access the hole easily with an allen key/drive from below.
RE: Pressure relief ball - Steve kay - 18-04-2023
This particular magneto engine being an assembly of new and properly sorted components, no plugs had fallen into the crankcase. This person however has learned something very very important indeed. Don't just count the number of valves, and the correct torque for tightening cylinder head nuts, but peer into the gloom alongside the oil pump and check that both the blanking plugs are still there! Whilst plugs are offered on web sites, doubts have been expressed about their origins and correctness. However, whilst Denny's Shipyard in Dumbarton long since closed down, two elderly chaps are still in a shed behind what used to be the prototype shop. There, on belt driven Drummond lathes they will make suitable items to correct spec, and a distinguished Scottish Seveneer has commissioned a plug or two. Full report in due course, the apprehension being why one plug is missing, and whether the replacement can just be screwed in or further work must be undertaken.
RE: Pressure relief ball - Steve kay - 15-05-2023
And the latest episode....
Blanking plugs in crankcase correct, new pressure relief spring and ball installed, engine reassembled...oh the excitement....still absolutely no better than before. Rude words, indeed very rude words indeed. Why, despite all advise, every suggestion followed up, and all steps taken, do we have no oil pressure?
Other entertainments have taken up some time but engine out yet again yesterday, and today dismantle the jolly little thing. No obvious problems with the pump, that is the pump with the mirror smooth cover. Relief ball seat not chipped. Plugs removed and access to galleries checked, no evidence of being blocked. So now what? Perhaps get an oversized oil pump body just because the thing is removed anyway, but what other suggestions? Gardening? Volunteering at the Oxfam shop? The 2CV passed its MOT this morning sans problem, the Ruby rumbles slowly in all directions, so why is the magneto engine proving so difficult?
RE: Pressure relief ball - Tony Press - 15-05-2023
Pump blades the right way up
Or are you like a local assembler who said that there was no oil pressure in an engine when only 2 psi was showing and he knew all his other engines gave 6 psi at idle.
I have never seen 6 psi at idle
