GHILA Posted January 15, 2022 Report Share Posted January 15, 2022 I have just added a differential drain plug to my 1980 Spitfire 1500. I only had 1/8" BSP taps available so that what I used. Might be considered a bit small, but I considered that I would not be draining on a regular basis so would be acceptable. When you think the oil in there had been in for at least 42 years, as I don't have the cars history. Drilled small 3mm hole removed filler/top up plug and drained oil out, after some days drilled and tapped bottom of casing with 1/8" BSP thread and plugged. Link to comment Share on other sites More sharing options...
Peter Truman Posted January 15, 2022 Report Share Posted January 15, 2022 eons ago I did my Vitesse but at the time late 70's I only had UNF taps so I tapped 5/16UNF as I had a brass plug of that size, now I'm better equipped and have 3/8in NPT and BSP taps and dies so I should probably redo it preferably BSP as it's not a tapered tap. It makes you feel better being able to drain the oil out at decent intervals. Link to comment Share on other sites More sharing options...
DerekS Posted January 15, 2022 Report Share Posted January 15, 2022 Evening all! I've drilled and tapped mine 5/16" UNF too, a couple of years ago and it's perfectly big enough when the diff and the oil is hot, it drains easily. A very worthwhile mod! Derek. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 16, 2022 Report Share Posted January 16, 2022 Nice job!! I don't need to tap mine, the oil runs out anyway.... Incidentally, what is the size? 1/4 BSP? Link to comment Share on other sites More sharing options...
GHILA Posted January 16, 2022 Author Report Share Posted January 16, 2022 No it is an 1/8" BSP, use a taper plug, the size is around 10mm OD. (3/8" in Old fashioned) 1 Link to comment Share on other sites More sharing options...
Badwolf Posted January 16, 2022 Report Share Posted January 16, 2022 1 hour ago, GHILA said: No it is an 1/8" BSP, use a taper plug, the size is around 10mm OD. (3/8" in Old fashioned) Is that the same size as the sump and gearbox drains? Making all the drains the same size means that you should always have a spare plug...... somewhere Link to comment Share on other sites More sharing options...
daverclasper Posted January 16, 2022 Report Share Posted January 16, 2022 5 hours ago, Badwolf said: s that the same size as the sump and gearbox drains? Making all the drains the same size means that you should always have a spare plug...... somewhere That's ideal. With my ltd experience of thread cutting, I would go small, so more chance of rectifying. Even so can't bring myself to have a go. Car only does low/laid back mileage anyway, so have just syringed out, most of old oil on occasion Link to comment Share on other sites More sharing options...
GHILA Posted January 19, 2022 Author Report Share Posted January 19, 2022 No its not the same as sump and gearbox, its smaller. I would guess they are around 1/2" BSP. To estimate BSP sizes which are based upon pipe size. eg 1/8 BSP + 1/4 = around 3/8* (10mm) OD. Therefore 1/2" BSP generally called 1/2" pipe when I was a lad are around 3/4" OD. Check these sizes on a thread chart. Link to comment Share on other sites More sharing options...
GHILA Posted January 19, 2022 Author Report Share Posted January 19, 2022 On 15/01/2022 at 20:47, Peter Truman said: eons ago I did my Vitesse but at the time late 70's I only had UNF taps so I tapped 5/16UNF as I had a brass plug of that size, now I'm better equipped and have 3/8in NPT and BSP taps and dies so I should probably redo it preferably BSP as it's not a tapered tap. It makes you feel better being able to drain the oil out at decent intervals. You can't get tapered taps, you have to drill and tap parallel and use tapered plugs. Link to comment Share on other sites More sharing options...
GHILA Posted January 19, 2022 Author Report Share Posted January 19, 2022 On 16/01/2022 at 18:32, daverclasper said: That's ideal. With my ltd experience of thread cutting, I would go small, so more chance of rectifying. Even so can't bring myself to have a go. Car only does low/laid back mileage anyway, so have just syringed out, most of old oil on occasion If we were 300 miles closer I would do it for you. Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 20, 2022 Report Share Posted January 20, 2022 Lidl were selling a 12v drain pump with selection of suction tubes for £10 that fit easy in through the filler hole if you dont fancy syringe or drilling options Pete Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 20, 2022 Report Share Posted January 20, 2022 I bought one; a mate uses one in his scrapyard to drain the brake fluid from scrap cars and he was impressed with them. I haven't tried it on engine oil yet, nor diffs either but the way all of mine leak I don't need to.... Link to comment Share on other sites More sharing options...
Peter Truman Posted January 20, 2022 Report Share Posted January 20, 2022 I brought a suction pump here in Aus think Aldi I found that none of the suction tubes would fit down the moderns dip stick hole as modern dip sticks and very small in dia didn’t work on daughters Commodore and Mazda. also with the gearbox and diff it may be difficult to navigate thro the fill plug and swing thro 90 degrees to get down into the oil to many internal obstructions gears etc in the way Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 20, 2022 Report Share Posted January 20, 2022 Hi, I thought the BSP Threads were BSPP or BSPT? Cheers, Iain. PS. Good job, I did the same & plugged with a brass 1/4 BSPT. Next time it's out I will be adding a small High temperature magnet to it. Link to comment Share on other sites More sharing options...
GHILA Posted January 21, 2022 Author Report Share Posted January 21, 2022 Hi SpitFire6, You are correct with the thread sizes. But these apply to the male threads only (Plugs). Female are parallel. Cheers, GHILA 1 Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 21, 2022 Report Share Posted January 21, 2022 7 hours ago, GHILA said: Hi SpitFire6, You are correct with the thread sizes. But these apply to the male threads only (Plugs). Female are parallel. Cheers, GHILA Thanks for that. Cheers, Iain. Link to comment Share on other sites More sharing options...
DerekS Posted January 22, 2022 Report Share Posted January 22, 2022 Evening all! Rather late in the conversation but I'm just sorting the garage at our new home and thought I'd post this pic of the drain I added to both the old (while on the car) and new (when off the car) diffs off my Spit 1500. (This is the old diff.) It's basically a shortened 5/16" UNF set screw with a thick washer and ptfe washer underneath. Drilling and tapping the cast iron was straightforward, it's good material to work with and both castings had a convenient dimple as a drilling point with the casting being plenty thick enough. I haven't had any problems with them. Hope this helps! Derek. 2 Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 23, 2022 Report Share Posted January 23, 2022 crikey Derek think you have gained a few hundred spaces in this the pics 2ft down the page you can edit the spaces out if you click the 3 dots to the right of the top line Pete Link to comment Share on other sites More sharing options...
DerekS Posted January 23, 2022 Report Share Posted January 23, 2022 Phew, thanks Pete, don't know what went wrong there but hopefully it's sorted. For some reason my phone kept saying the website was not responding... no wonder! Thanks again. Derek. Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 24, 2022 Report Share Posted January 24, 2022 thats better , technology is a wonderful thing when it works bring back true print and the duplicate book we waited nearly an hour for a lunch when the printer in the cafe kitchen had run out of till roll . no one new this ....so it never arrived the best bit the refund was more than the till price as the refund techy couldnt get round the club card discount(we received but dont belong) so techy won me £6 Pete Link to comment Share on other sites More sharing options...
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