Drain Plug thread size

[Peter L]

Hi,

I have just removed the drain plug from my Major to drain the engine oil. Looks like the plug has either been cross-threaded in the past or is of incorrect thread pitch as the thread is in a poor mashed state. The plug looks like its made of brass and has a square head with flange (it almost looks like a end stop for plumbing?). I want to replace it with a new plug and want to make sure the size is correct also I want to get a thread tap to retap/clean the thread in the sump (just in case). Measuring the diameter of the plug (not the hole) it looks like a 3/4 inch diameter with thread pitch is about 2.3mm per turn (I measured 7mm for 3 turns) which is close but not quite a UNC thread pitch (2.54mm). When I go on line to see if I can get a drain plug for a major they are all 7/8 UNF threads with a hex head. https://www.agrilineproducts.com/sump-plug.html. Does anyone know what the correct engine drain plug should be for a 1957 diesel major E1A?

[henk]

Peter,

Mine has a hex and needs a copper ring to seal. I'm not sure but I think it's metal. The plate were it sits in is from aluminium.
Seems to me the treath was damaged and someone put a plump stop in it. Best to get the plate of and examen the hole.

[Peter L]

hi henk,

I dont have the aluminium plate, sump is of the newer type without a plate, so I guess it's cast iron?? (maybe wrong about that). I hoping the previous owner for some reason replaced the plug with a brass stop because they had nothing else as opposed to the thread in the sump is damaged. I hoping brass is softer than cast? so I just need to get the right plug.and the thread in sump just needs a clean with a thread tap. Otherwise I'm going to have to redo the thread with a larger size which will be a pain

[henk]

Fingers crossed for you Peter.

[Peter L]

Thanks,

Having spend several hours examining the hole and the thread I think it's a 3/4 BSF (12 threads per inch). 7 turns for 15mm when measured with my vernier. I even used some blue-tack to take a impression of the thread in the hole. BSF is that a usual thread size on a Fordson major? I thought the "normal" imperial threads sizes on a Fordson Major where UNC/F? Anyway off to ebay to buy a bolt first to see if the thread matches.

[oehrick]

For many liquid containing and particularly tapered threads BSP (British Standard Pipe) is a common thread rate,even in Metric countries, the 3/4 BSP however has a 14 tpi thread rate but if your BSF Bolt does not fit, might be worth checking, the parts list infuriatingly does not specify the rate

[Peter L]

The 3/4 inch BSF stainless bolts I managed to find on ebay and have bought fit perfectly phew. Unfortunately the size is quite rare hard to find; all I could find were 1.5 inch stainless bolts without having to get someone to make some bespoke ones. I'm in two minds whether to cut down the length to size (will a 1.5 inch bolt matter?), Then use a 18mm bonded copper seal washer (dowty washer). So hopefully that should not leak. I guess with a proper drain plug the surface of the bottom of the plug head is precisely machined where as a bolt is less precise.