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MG Midget and Sprite Technical - Dual gauge install: remove this screw?

New dual gauge going in, the oil feed connection has a tiny screw in the feedway (1st pic). Is this supposed to be removed prior to install?

Archive searches across the internet about dual gauge installs keep showing images similar to 2nd pic, i.e. a gauge with no visible screw in the feedway. Granted, that screw could be greasy/invisible and/or it is slightly recessed, but only slightly.

The lack of mention anywhere is screaming out "leave it be!" Should it stay or should it go now?




Richard Reeves

I've never seen or at least noticed a screw there. Is it a new Smiths gauge?


Other than that;

Good song, you might as well listen while someone digs out a spare and posts a picture.


https://youtu.be/BN1WwnEDWAM?feature=shared

anamnesis

No screw in my spare oil gauge. How will the oil get to the sensor otherwise.

If still concerned about removing it, you could try an airline or footpump on it (gently), see if the gauge needle moves.

Or install and test with oil.
Tim Carter

I just checked the dual gauge I have sitting in the workshop and no screw and no internal thread to take one. I wonder if it might be a restrictor to damp pressure fluctuations not that I've ever seen that needed. Tim's idea of an air line will likely give an indication, mine did and flicked up to around 20 psi with quick blast.
David Billington

No screw in this new one either.

I wondered about it being an adjuster too. Hence my question on the make of gauge. It doesn't look the same as my smith or this new one.

anamnesis

Could it simply be a protective screw to prevent contaminants entering the orifice before installation?
Bill B

I think a protective screw unlikely when a plastic cap would do the job and almost certainly be cheaper than machining the screw and tapping for it. Nothing really to harm in the inside of a Bourdon tube anyway.
David Billington

I've never seen one like that. What happens if you press it in? does it feel like it is spring loaded or is it solid?
Rob
MG Moneypit

Gauge purchased new from W.H. Motor Spares Telford, Shropshire January 2006 by me. Interestingly, receipt says "MG Dual gauge", not "Smiths Dual gauge". Gauge face says "Smiths made in U.K." but I did notice the 2 scales are rather more separated from each other than the usual. No identifying marks other than the face. Gauge body is black, not silver. Three screws on gauge backside seem unusual as well. Paid $81/60 quid 19 years ago.

I thought protective as well, but Dave's point as to the economy of that rings true. Bracket doesn't look standard either. What about that screw terminal for the panel lamp hot wire at the top of the black tube: is that customary?

I'll try to get some pressure on it and look for a response.


Richard Reeves

Pressure test would be the best bet--
I doubt they'd fit a screw in where it could be easily overlooked like that------unless it's a million to one chance that a spare screw from assembly has found itself living there--if so it wouldn't be threaded or tight and should just tap out-
It'd be a shame to remove it if it's tight and something falls off inside.
willy
William Revit

Perhaps it's a screw for factory calibration of the bourdon tube. Adjusted and set and then not to be altered?
GuyW

Without removing screw, gauge registers when on the compressor. Near identical reading to compressor gauge.

Conclusion: Don't mess with the screw.

Richard Reeves

Good to hear.

Out of interest, what does the connector on the end of your pipe look like (the one that goes on the gauge) ? Did this pipe come with the gauge ?
Tim Carter

Pipe came with gauge.
Why it's fat and not the capillary type I've seen IDK.
Same fitting both ends, fits my BSP to NPT adapter so 1/8" BSP 27 TPI I'm assuming, tiny gaskets required.

Richard Reeves

Oil pressure pipe looks quite a bit larger than the steel original pipes I'm used to, I wonder if the plug is needed to damp fluctuations as I suggested before which might have been done previously by the small bore tube. Anyone have any dimensions OD ID for an original steel oil pressure tube?

1/8" NPT is 27 TPI
1/8" BSP is 28 TPI, I presume in this application it's BSPF (G) rather than BSPT (R).

In the small sizes NPT and BSP are often interchangeable especially if the thread engagement is short.
David Billington

“ Anyone have any dimensions OD ID for an original steel oil pressure tube?”

I’ve just measured a couple of tubes that I have in the garage. The ODs measured 0.123” and 0.129”, so near enough 1/8”. The IDs measured 0.050” and 0.060”, although the discrepancy could be due to burrs on one of them, or maybe both.
Dave O'Neill 2

This thread was discussed between 26/08/2025 and 28/08/2025

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