British Standard pipe and National pipe thread

ScottNC

Member
I need to replace the water temp gauge and install an oil pressure gauge on my DB885. I want to use easily sourced gauges and sending units which means National pipe thread. A search indicates it is possible to join the two with suitable sealer. Ralston Instruments makes adapters. Since the British version is 55° and National is 60° it should be possible to run a tap into the Brit's holes providing the hole doesn't become too big in the process.

What have those of you who have dealt with this before done?
 
It depends on the size, 1/2 and 3/4 have the same TPI (thread per inch), so they will generally work with sealer. Not perfect, but doable.

All other sizes are different TPI and WILL NOT WORK! Even running a tap in will cause the threads will be damaged, it will leak. An adapter must be used.
 
I usually just buy an adaptor. The threads are not the same pitch even on the common sized ones. They will usually still leak over time. So just buy the $5-10 adaptor and be done.
 
(quoted from post at 18:55:27 04/01/18) I usually just buy an adaptor. The threads are not the same pitch even on the common sized ones. They will usually still leak over time. So just buy the $5-10 adaptor and be done.

That was my thought, as well, 'til a re-read it and saw he was working with a temp gauge, as well.

Using an adapter/pulling the heat sensitive element back out out the block isn't the best idea, IMHO.

Dunno what his best BSP gauge option would be, tho.
 
Bob some of the adaptors for these elements only raise them maybe a 3/8 of an inch. They are kind of a double sleeve deal. He would take out the factory adaptor and put this one in that has the NPT on the inside.
 
Scott, the oil sender unit is a standard GM sending unit, so just buy a gauge kit for your chevy hotrod. Same as the temp gauge.
 
Steve's experience matches mine, 1/2 and 3/4 will work under low pressure with the good sealant. Others not. For anything important that cannot leak go to McMaster Carr, find the adapter, look at the price, then grin and bear it.
 
(quoted from post at 22:39:04 04/01/18) Scott, the oil sender unit is a standard GM sending unit, so just buy a gauge kit for your chevy hotrod. Same as the temp gauge.

So the oil and water sender holes are NPT not BSP? I've not pulled either sender yet, found the water temp gauge to be junk only yesterday. I'll buy an aftermarket gauge and see how the stock sender matches up to it. The factory 885 oil sender is for an idiot light, I'll pull that one tonight to verify the threads.
 
One other consideration, automotive gauges typically are designed for use protected from the weather.

Unless the tractor has a cab, the gauges may soon fail from water, sun, and dust exposure.

Tractor or marine gauges would be a better choice.
 
(quoted from post at 05:16:22 04/02/18) One other consideration, automotive gauges typically are designed for use protected from the weather.

Unless the tractor has a cab, the gauges may soon fail from water, sun, and dust exposure.

Tractor or marine gauges would be a better choice.

Very good point. I have access to marine gauges via a neighbor (Hatteras in High Point, NC), but from using a 2N Ford for years I got in the habit to never leave my stuff out at night if I want it to start. I'll go with automotive.
 

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