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Drain plug

sonama

Member
I have a problem with one of my drain plug. The part number is 127951 and it says (plug, water jacket drain) but does not tells the type of treads. It is 1/2 inch but I would like to know if it is NPT or straignt treads? The one on starboard side works fine but the one on port side is very hard to tighten and scrap the treads so I want to buy a tap to retap the hold in the motor but want to be shure to buy the right tap. Thanks for your help. Jean
 
I rechecked the picture and I am not shure that I have the right part number but I am shure that it is a 1/2 inch. plug that and that it is a drain plug.
 
Sure would help if you gave some specifics....

The part number in Post #1 is a 1/4" NPT plug...

As a rule, drain ports typically use NPT threads and, except for those with zincs, get PST when reassembled...
 
There is one such a plug on each side of the motor. It is situated Under the manifold at a pretty hard to get place. When I search the parts catalog that I bought from our sponsor here, it is not clear on the diagram which one it is. First I tought that they were the part number I mentionned in my first post but after double checking I found out that they were 1/2 while mine are 1/2. I have 2 here and I checked again and effectively they are 1/2 so the part number might by 444705 but like I said earlier I am not shure that this is the right one either so I am wondering if there are other drain plugs somewhere else that would not be mentionned in the parts catalog and if so if the tread is NPT or something else? Thanks again for your help.
 
If you are referring to the coolant drain plugs on the side of the block, yes - one on each side.

When you reference an object as "1/2", it benefits those that can only read what you type by adding more details: units, like inches or mm, and what parameter you are describing, like diameter or the wrench that fits the hex head.

There are usually drain plugs on the lower end of each exhaust manifold and the elbows too....the newer manifolds are not side specific and will have a drain on each end.
 
A 1/4" NPT plug is close to 1/2" diameter. Of course, NPT is TAPERED and therefore is never specified by its diameter. THe 127951 is the plug used both in the block and in the exh manifold for coolant draining. I don't know of any water plugs on my engine that are not NPT. btw, what engine are we talking about? :p
 
A 1/4" NPT plug is close to 1/2" diameter. Of course, NPT is TAPERED and therefore is never specified by its diameter. THe 127951 is the plug used both in the block and in the exh manifold for coolant draining. I don't know of any water plugs on my engine that are not NPT. btw, what engine are we talking about? :p

Sorry, I should have given more détails. Here they are: Mhy engine is a Crusader CH270. By the serial number it was build in 1986 and it is raw water cooled. The manifolds are the old type, log type. I am not a mecanic so I don't know much about engines but I have a tool to mesure the plugs and this one fit in the hole marked 1q/2 and the tread fit with the ones marked 18tpi. When I search the parts catalog that I ordered from our sponsor up here, there are two such plugs, one is part number 127951 and the other is 444705 and I am not shure which one is the right one because it is pretty hard to find out by the drawing for a newbe. Thanks to all for your precious help.
 
you want the 127951 part....

If you want to save a little cash, you can get a "1/4" NPT plug" from any decent hardware or autoparts store. Brass is preferred but the ferrous ones will work. Use Loctite PST or a similar teflon based thread sealer when you install the new one.
 
I used a 1/4" NPT tap to clean up the threads in a block for the drain plug many years ago. Either it was really corroded or I just went too deep. When I put in the plug it screwed in way too far. With a little looking I found a plumbing supply place that sold "oversize" plugs (really "over length", getting much fatter at the top). Worked like a charm.
 
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