Morgana

It's not 7/16" UNF at all. The thread profile is wrong and the 7/16" UNF nut that's just arrived doesn't fit. Left to right in the picture: original; 1/2" UNF from the fuel pump; new 7/16" UNF. Looking more closely, it's a very good fit for M12 fine. This is 1.25mm pitch, which is 20.3tpi - an easy confusion to make when expecting 1/2" or 7/16" UNF which are both 20tpi. This would also tally with the metric top cover screws in the bizarre M5x0.75 thread... Automec have a possibility which I will try next. Flexolite show a banjo fitting with M12x1.25 described as 'Solex Carburettor Thread' so I think I'm on the right track.

That's not a bad idea. I think the olive on one of the spigots on the original fuel pump is soldered. I guess not something to do with petrol around! Would you align the end of the olive with the pipe, or have some projecting?

Late to the party, but this thread (ha!) came up while I was looking for parts for my Solex. The thread for part 72 on my B30 PSE1 is 7/16" UNF - it's noticeably smaller than the 1/2" UNF fuel pump tube nuts, and the latter don't fit the former. Canley say the nut is unobtainable. I'm investigating a solution. Edit: It's not 7/16" UNF at all. The thread profile is wrong and the 7/16" UNF nut that's just arrived doesn't fit. Left to right in the picture: original; 1/2" UNF from the fuel pump; new 7/16" UNF. Looking more closely, it's a very good fit for M12 fine. This is 1.25mm pitch, which is 20.3tpi - an easy confusion to make when expecting 1/2" or 7/16" UNF which are both 20tpi. This would also tally with the metric top cover screws at the bizarre M5x0.75 thread... Automec have a possibility which I will try next. Edit again: Flexolite show a banjo fitting with M12x1.25 described as 'Solex Carburettor Thread' so I think I'm on the right track.

That does look similar, thanks for the Google-fu johny! The proportions look different from the one I have though (I've tried to make an equivalent perspective picture, attached), so I called Gower and Lee again but they only open Monday-Wednesday. I did get through to Canley Classics, and they say they don't do a B30 PSE1 kit because this nut is unobtainable! So perhaps there's more to it than meets the eye. I'll get one of the ones you show and do another comparison.

It's similar - the fuel pump is 1/2"-20 UNF as you say, but the Solex is 7/16"-20 UNF on the same 1/4" pipe (which has been, as one might think, confusing). I haven't done work on the brakes enough to get to know the fittings, but I'm aware of the principle of flared ends. The original fuel pump I've got had steel pipe ends (so presumably original equipment) with olives on in the inlet and outlet. The original nuts are both some yellow metal and have a cone/chamfer on, with the new olives I have sitting into the nut by a small amount. I have seen some on eBay and other retailers that show pictures of the business end where it isn't flat, but often advertised as for brake pipes. I imagine it's a bit of suppliers not knowing, buyers not knowing and variation in the manufacture. From a purely mechanical causality perspective, it seems logical that the olive ought to be compressed from both sides. If a flat-sided nut is used, the edge of the olive will be pressed forward and the shaped recess in the carburettor will compress that end, but the other will not be suitably shaped. In extremis, I could machine a truncated cone of the right angle into the end of the nut, but for something sitting over the hot manifold it would be nice to get it right first time! The new one's a lot longer, too. I've not been able to find a part at Canley from the diagram, as their 'fuel' section stops at the pump inlet, and the carburettor doesn't have a piece of pipe associated with it. Aside, my pump to carburettor copper line is cable-tied to a mount at the front of the water pump, but from reading on here I understand it was originally rigidly mounted with one of the bolts for the pump to some sort of clip. The pipe I had to file the swage off in order to remove the useless olive and nut from is quite ropey, so I was considering replacing it with the cupro-nickel length I have just bought, but if doing that I may as well mount it robustly to the pump if that's where it's supposed to go.

I got some nuts, olive and pipe in an order today. However, I think the nuts are for double flares rather than olives, as the ends are flat. Am I right in thinking they ought to have a conical inner surface to compress the olive successfully? Attached is a picture of the mashed nut off the carburettor (originality unknown, but with a flared inner surface) and the new one. I've not heard back from Gower & Lee to see if they have pipe nuts to match the carburettor. It's tricky as most of these fittings I've found are advertised as brake rather than fuel, so aren't made for olives. I understand olives are not suitable for brake lines as the pressures are too high, hence the flare fittings for those applications, and the alternative styles of 7/16-20 nuts...

Thank you both. Pete L - I don't think I'll be sure of anything again after my experience with the M5x0.75 thread on the float chamber cover! 😁 PeteH - 1/4"BSP actually measures ~1/2" across as it comes from the bore size of steel pipe, and allows for threads to be made on the outside. In this case, the outside diameter of the thin-wall fuel pipe is 1/4" and the fitting will be made with an olive and a male tube/pipe nut. The examples I've seen for sale of this type of nut are UNF or metric. I have found a chap locally who has boxes of spares and is going to have a rootle for me. I'll see what he turns up...

I've not been able to get hold of Gower and Lee, and can otherwise find no reference to this part on the carburettor drawings. The pipe nut holding the fuel pipe into the carburettor was mashed on first getting the car, and didn't fit any metric or imperial spanners. After a weep where the only way to get it to stop was really mashing the nut, I need to redo the connection. It's an olive compression fitting, and since I find the olive can rotate on the pipe, which has flared out slightly beyond the olive, I guess this is the source of the poor seal. Flexolite for example have a 7/16" nut for 1/4" pipe, but with prior experience of unusual metric threads on the carburettor cover I think it's as well to seek further expertise... In passing, does anyone have concrete evidence that the carburettor's name is PSEI or PSE1? The Solex manuals are inconclusive as the sans serif typeface makes the numeral and the capital letter look identical! I'm tempted to think it's an 'i', since Gower and Lee who sell the parts have a PSEI-2, which would imply PSE2 if it were a numeral.

I think this is exactly what's happened with my carburettor joint. The pipe is visible as a tiny lip just after the olive, which can't slide off, so getting a seal into the alloy carburettor housing with the male pipe nut is very difficult.

I have read in a Yanmar 2GM20 marine diesel manual to rev the motor high, then turn it off (fuel cut-off valve), which is specifically advised instead of turning off after idling. The explanation was to do with removing burnt residues, but then there isn't any fresh fuel coming in as it's been turned off with the valve.

I'm on my way to Edinburgh for Hogmanay and have some irritating fuel weeps at the Solex, and a random conk out on a dual carriageway in today's torrential downpour, although luckily next to a layby which I coasted into. No obvious gremlins under the bonnet and it started up again straight away and was fine to tonight's hotel. I've been meaning to do something about the carburettor for a while, as the fuel inlet pipe has never fitted well (the pipe nut is chewed and rounded and the pipe flare/olive doesn't seat well, so I guess this has been a historic problem). However, B30 PSEIs seem to be thin on the ground, so the only option would be to shell out several hundred for a refurb and have the car off the road for a while. Assuming I make it the remaining 250 miles tomorrow, if I feel the gasket on the carburettor needs doing or anything untoward occurs, can anyone recommend a garage in Edinburgh likely to have spares, gasket paper and/or Herald expertise I could visit next week before the long trip down south?

Thank you all for the suggestions. Mechanical attachment seemed the way to go, so I have attempted a mechanical solution which I'll mount in the morning. I think I'll need it as I'm off to Scotland tomorrow where the heater's probably going to be required going by the weather forecast. I drilled four small holes around the circumference of the knob assembly, then mounted the cable sheath and continued the holes into it. I pressed 5/32" lengths of paperclip into the holes along with some Araldite around the circumference and the mating surfaces. I filed the paperclip ends off flush and finished with some adhesive-lined heatshrink. The knob can now be pushed and pulled with the distribution flap moving successfully. I hope the shear strength of the paperclip pins will hold the sheath against the stress of pushing the knob, and the heatshrink/Araldite will prevent the two pieces moving against each other too much and loosening the pins. Time will tell...

I see you've recommended butyl gutter sealer a few times - I've got a leak in the corner of the screen and was going to pump some in. In the hardware shop the back of the tube specifically said not to be used in contact with glass which gave me second thoughts. Any idea why this could be, since butyl tape is what glaziers use...?

I wouldn't worry about it if I were you. Lead acid batteries have a finite life. As long as there's a charge current to replace that drawn when starting, and it retains that, all is well. It's impossible to tell the state of a battery during charging using a voltmeter, as any voltage reading is only indicative of anything once the cell has settled with the charging current removed. I guess if you were particularly keen to have the most long-lasting charge possibility then some complex circuitry to make a 'smart' charger would be best, rather than the simple increased resistance to inward current flow the cars rely on. Good information here. Personally, the ignition light and a check with a meter and hygrometer if the starter's turning slowly are all I think are necessary with these cars. The battery will need replacing whatever you do every few years, so I wouldn't add to that with worrying about regular data points.

Mazac! That's it! Well remembered. I can see soldering coming a cropper - a big Magnastat will be getting on for 500C and there's a lot of heatsinking going on. Mr Truman's mechanical idea is probably less likely to go wrong, if I don't crack the casting. I just don't understand how it's never been attached, unless the switch mechanism and cable are the wrong parts, perhaps off a different car. The cable is the right length, and the cable sheath end fits into the casting, but that's as far as usefulness goes.

Well that shows very clearly that mine is not right. There's no sign of tampering, or a broken fixing or casting - yours looks very securely connected by contrast! I just have a clean recess down to the hex-reamed tube for the detented slider, and a smooth circular outer cable end. It certainly is non-ferrous, and has that greyish look of that die-cast alloy that doesn't take well to anything like solder. I guess I can try with some aggressive flux as there's nothing to be damaged by the heat, and those in your photograph do look 'wetted' by something. There's no retaining ring marked in the exploded diagrams I've seen, but then the pictures are very small and the knob assembly is shown as one element. Either it's something the PO got wrong as a replacement part (the grub screw it came with was a wildly wrong thread, too and this mechanism has never been connected so far in my ownership); or it's never been soldered.

Aha, that would explain it if they're supposed to be a single entity. Funny, there's just a smooth recess on my switch housing with no hint of having been crimped or more permanently attached. Thank you.

I still haven't got this working satisfactorily. I've trimmed the felt down several times, as it moves freely off the car and binds as soon as it's inserted and the nuts put on to fix it. Now I'm struggling with the air distribution control on the dashboard. It pulls out fine, but on trying to push it in the outer cable sheath just moves back with the inner wire, thus failing to push the flap back. There is no way for the outer sheath to fix to the control slider, as it's only clamped at the distribution box end. Should there be something else to hold the cable hard against the dashboard control?

I've taken off the furry large bubble seal in favour of a new flipper seal from East Kent Trim Supplies. It looks the business and feels nice. Not furry either. The PO seal was joined at the middle of the bottom horizontal run. On the MGBGT it's a self-cut mitre at the top rear corner of the opening. I can't see anything in the workshop manual or Haynes, so any consensus on the best joint location?

With three blown downpipe gaskets in 18 months of ownership, I am fed up with stripping brass nuts trying to get a seal! Now I've found the downpipe ought to have another bracket on to steady it, I hope these ones will tighten up and not need to come off any time soon...

That's a great find, chrishawley! Your Google-fu is better than mine. I can however imagine some members might baulk at sending money to the MG register! Too late, however - I made these and they are ready to be tested before cleaning up... They're phosphor bronze rather than the aluminium bronze in your link. I wonder what the difference might be. This was not the easiest to machine. Quite 'bitey'.

I've never worked on anything automotive that old, but I understand that as mentioned above, tooling from BSW/BSF plant was still around, especially in the somewhat hidebound UK motor industry. There's one story that some Morris engines had metric threads with Whitworth heads on as the company took over a French factory and didn't want the expense of either changing their British spanners, or the French machines! It may be that Triumph always used Unified post-War, but in a general sense when working on pre-1960 objects, tooling of the period could possibly have a variety of thread types that weren't completely converted. I think by the '60s it would have changed over completely in the motor industry. The only reason for the change I'm aware of was the huge influx of American machine tooling and vehicles during WWII, and the need for associated maintenance equipment. Their 'National' series of threads (NF, NC, NS, NP etc.) ended up being chosen as the new standard post-War, renamed to Unified National, hence UNF, UNC etc. British Association (BA - perhaps the mathematically most satisfying thread form) continued for a long time as the standard for instrumentation and electronics, rather than the smaller UNF sizes - I think it's still not completely unusual to have 4BA screws in pattress boxes. Of course, there's the added fun that Whitworth has the original head size (BS190) and then the smaller hexes from BS1083 in which the head size matches the BSF example of the same fastening size, so for some spanners you may find yourself using the size below that which it's stamped with... A big Whitworth spanner is a lovely thing - remember the size refers to the major diameter of the thread, rather than the measurement of the head as in AF spanner sizes. When I would need to use my 1.1/8"BSW one unless I were building an icebreaker, I don't know!

NPT is National Pipe Taper - American. Also NPS (National Pipe Straight). American air tools (Chicago Pneumatic for instance) have NPS or NPT female threads, and people often insert BSP hose tails with a large spanner as GrahamB says. Not a good idea, and most inelegant. UNF and UNC is very useful for your Triumph, if it's 1960s onwards. The smaller sizes (10-32 etc.) are also used on things like front grille screws.

I have a 'car' cantilever toolbox in the shed as I need to carry it around to where the car is. It has Imperial spanners in. There's an AF roll in the car (in African wax print) which brings me joy. Yes, I mentioned the eBay ones earlier, as did Mjit. I think we all agree they're not worth it when I have a bronze hex bar on the desk. I don't know why you're mentioning Spalding Fasteners now - I think we're going round in circles! I refer you to the previous page:

More practicality than originality. Coming across something that ALMOST fits a spanner and doesn't quite because what the manual said was 1/2" is 13mm is not fun to my mind. I don't have room for a metric set of spanners in the kit as well, and appreciate being able to use the same AF three for almost everything! Oh, and BA is my favourite thread so a cute set of those is a must for electrical work...