Misthreaded K Series Oil Plug

[jellyghost 378]

I messed up the threads on my oil drain plug.  Its for a 1978 10hp K Series (K241AS).  When I called a small engine shop, they said the oil pan is aluminum, and it will need rethreaded too.  The oil pan seems magnetic, so these guys may be off base...

Is the pan aluminum?

Where can I order a new plug?  I can't find anything online that looks the same as my current plug.

Is there a trick to rethread the tapered part of the plug?

 

Does this thing work?

https://www.jthomasparts.com/125-508-oil-drain-valve?gclid=EAIaIQobChMI3uq3tqXk4QIVxbjACh2vKg85EAQYAyABEgILvvD_BwE

[Achto 29,220]

18 minutes ago, jellyghost said:

Does this thing work?

 

 That would work, I have some thing similar on my truck made by Fumoto.

 

The plug on your engine should be a common pipe thread size, 1/4 or 3/8 npt. I would purchase the correct pipe thread tap and retap the hole your self. To help keep the chips that will be created from taping the hole out of the engine, pack the tap full of axle grease. The chips will stick to the grease instead dropping into the oil pan.  

Edited April 22, 2019 by Achto

[jellyghost 378]

If I retap the hole, that assumes the hole has a problem.  I am not sure it does (more likely if it's aluminum).  If I do that, should I buy a wider oil plug of any thread and just enlarge the hole?  Are you saying that I don't have to remove the oil pan to retap it?

[The Tuul Crib 7,338]

34 minutes ago, Achto said:

 

 That would work, I have some thing similar on my truck made by Fumoto.

 

The plug on your engine should be a common pipe thread size, 1/4 or 3/8 npt. I would purchase the correct pipe thread tap and retap the hole your self. To help keep the chips that will be created from taping the hole out of the engine, pack the tap full of axle grease. The chips will stick to the grease instead dropping into the oil pan.  

[The Tuul Crib 7,338]

50 minutes ago, jellyghost said:

I messed up the threads on my oil drain plug.  Its for a 1978 10hp K Series (K241AS).  When I called a small engine shop, they said the oil pan is aluminum, and it will need rethreaded too.  The oil pan seems magnetic, so these guys may be off base...

Is the pan aluminum?

Where can I order a new plug?  I can't find anything online that looks the same as my current plug.

Is there a trick to rethread the tapered part of the plug?

 

Does this thing work?

https://www.jthomasparts.com/125-508-oil-drain-valve?gclid=EAIaIQobChMI3uq3tqXk4QIVxbjACh2vKg85EAQYAyABEgILvvD_BwE

The k series have cast iron oil pans 

[ebinmaine 71,734]

25 minutes ago, jellyghost said:

If I retap the hole, that assumes the hole has a problem.  I am not sure it does (more likely if it's aluminum).  If I do that, should I buy a wider oil plug of any thread and just enlarge the hole?  Are you saying that I don't have to remove the oil pan to retap it?

I'm assuming it's probably pretty tight quarters in there but is there anyway you can get some pictures?

I'm not sure why your small engine repair shop would be telling you that is aluminum unless they are making an assumption based on a lack of experience with older engines.

 

I think I would do exactly what Dan said above and get the appropriate tap.

Take your drain plug right to a hardware store or whatever big-box place you're going to get the tap and match it up by size.

 

It's entirely possible that it is only the first two or three threads that are messed up.

A tapered tap would fix that.

[ebinmaine 71,734]

30 minutes ago, jellyghost said:

If I retap the hole, that assumes the hole has a problem.  I am not sure it does (more likely if it's aluminum).  If I do that, should I buy a wider oil plug of any thread and just enlarge the hole?  Are you saying that I don't have to remove the oil pan to retap it?

I'm assuming it's probably pretty tight quarters in there but is there anyway you can get some pictures?

I'm not sure why your small engine repair shop would be telling you that is aluminum unless they are making an assumption based on a lack of experience with older engines.

 

I think I would do exactly what Dan said above and get the appropriate tap.

Take your drain plug right to a hardware store or whatever big-box place you're going to get the tap and match it up by size.

 

It's entirely possible that it is only the first two or three threads that are messed up.

A tapered tap would fix that.

[wallfish 17,833]

45 minutes ago, Achto said:

 

 That would work, I have some thing similar on my truck made by Fumoto.

 

The plug on your engine should be a common pipe thread size, 1/4 or 3/8 npt. I would purchase the correct pipe thread tap and retap the hole your self. To help keep the chips that will be created from taping the hole out of the engine, pack the tap full of axle grease. The chips will stick to the grease instead dropping into the oil pan.  

The need to re-tap the threads in the oil pan depend on how hard you tried to crank the plug in. The cast is harder than the steel plug so it's possible just the plug is boogered.

[Achto 29,220]

56 minutes ago, jellyghost said:

  If I do that, should I buy a wider oil plug of any thread and just enlarge the hole?  Are you saying that I don't have to remove the oil pan to retap it?

 

I would retap it to the same size that it was. Basically you'd be just chasing the thread in the hole to straiten them out. There should be no reason to remove the oil pan to do this. If you pack the tap full of grease before using it, the grease will capture any shavings created. If you want some second assurance you can dump a quart of diesel, followed by a cup of oil in the engine before you put the new plug in. This should flush any missed chips out through the drain hole. 

 

If the threads are so bad that this does not work then you may want to step up a size on the hole. Another trick that I have used is to purchase a well nut and use it as a drain plug. Find one that fits snug in the drain hole, insert the bolt with a washer on it, when you tighten it down it will expand and plug the hole. It will also remove fairly easily by loosening the bolt back up so that it will contract again.  Crude but it works like a charm.

 

https://www.lowes.com/pd/hillman-10-24-x-5-8-in-rubber-standard-sae-well-nut/3012493?cm_mmc=shp-_-c-_-prd-_-tah-_-google-_-lia-_-126-_-fasteners-_-3012493-_-0&kpid&store_code=2304&k_clickID=go_625706834_34613750110_111132558790_pla-78266456166_c_1016367&gclid=EAIaIQobChMIhK3e8rfk4QIVh2SGCh0ldQYSEAQYBSABEgKfnPD_BwE

Edited April 22, 2019 by Achto

[jellyghost 378]

Here is the update...

Finding out that the plug is pipe threaded was a huge break through.  Thanks! 

The plug is a quarter inch pipe thread, and I cleaned up the threads by working it into a 1/4 inch pipe elbow.  When I screwed into the oil pan, it finally caught the threads, but then it got too tight.  We leave town tomorrow, and the lawn is wild prairie right now.  My wife has humored me with this hobby, but she was going to shoot the WH if it can't mow today.  So... I kept screwing in the plug even though I knew it wasn't quite right.  I just committed to doing a bigger fix when time wasn't pressing.

This morning I bought a 1/4 inch tap, but I really like the simplicity of the well nut solution.  Are you sure that the well nut rubber will stand up to the heat?

Thank you for saving my horse from the glue factory!

[ebinmaine 71,734]

1 minute ago, jellyghost said:

Are you sure that the well nut rubber will stand up to the heat

might not be the correct way to fix something in some situations but in the distant past I've seen people use those on full-size cars so you should be all set as far as the heat at the very bottom of an air-cooled engine.

[Achto 29,220]

23 minutes ago, jellyghost said:

but I really like the simplicity of the well nut solution.

 

I've used this solution on air cooled engines without issue. I also used this method on a Shovel Head Harley tranny. A PO had either over tightened or cross threaded the drain plug. so the first time that I changed the tranny fluid was also the last time that the plug would tighten down. A well nut served as my oil pug for 3 years without issue. I did how ever tap the hole out for a larger plug when I rebuilt the transmission.  

[bc.gold 3,406]

Heli-Coil Pipe Thread Inserts

https://www.stanleyengineeredfastening.com/-/media/web/sef/resources/docs/heli-coil/pipe_thread_inserts_hc903-rev4.ashx