Morgana

A photo would be very helpful! I haven't personal experience of fixing one, but I can't think it's too complicated to reverse-engineer if you have a good picture of both sides of the circuit board.

Yes, they're all the same. Sometimes you see 1/4" audio plugs called 6.3mm as well. As Pete Lewis says, they're just metricated Imperial measurements. I get bags mostly from Auto Electric Supplies as they have good quality parts, a navigable website and a good paper catalogue. I use uninsulated Lucar connectors with a proper ratchet crimper when I'm not using bullets (Imperial, not Japanese which really are metric), covered with insulated boots. Stuffing weather-prone insulating sleeves with grease helps mitigate corrosion. I used to use silicone grease until I read enough about its problems to start using lanolin grease instead. Nicer on the hands, and doesn't affect the paint touch up...

Thanks all. In the light today, perhaps they're not as worn as I thought. The dips look quite shallow so I might get away with it for a while. The offside cylinder doesn't slide unless whacked - it seems much tighter than the nearside one which can be slid back and forth by hand. Should I put a smear of grease behind them? I wonder if both trailing shoes have been put on upside down, too. I haven't had the brakes apart yet, and having consulted the manual it looks as though the trailing shoe ought to have the rectangular hole downwards, but both sides have it upwards.

I'm tagging onto the end of this thread to help with search results. I have similar grooves in my backplate. Without the special hub puller, has anyone had success welding and grinding it in situ? A couple of passes with a 2.5mm rod ought to do it, and a small rotary tool could get it flat. Otherwise, I guess the whole hub has to come off to get at the plate... Wouldn't this issue be solved if the handbrake lever pivots didn't project beyond the grooves in the cylinder housing? I'm sure the photographs I've seen have them sitting proud in the casting.

As rogerguzzi says, everything you need you can get from Screwfix or your local hardware/electrical shop if you're lucky enough to have one to support. 2.5mm2 is wild overkill, unless you have a gigantic cable run. The conductor size is for ensuring low resistance to current per unit distance, and to avoid the copper wire acting like a fuse, heating up and melting while setting fire to the insulation. This might happen if you used USB mouse wire to power your motor, for example. Your photograph of the plate says 2.2A for your motor. 1.5mm2 cable is rated for 15A at 240V. I'd use that simply because it's a little more bulky, robust and less likely to get snagged on anything than 0.75mm2, though that would be equally acceptable electrically. Consider that an old Kenwood Chef motor is about 1/2hp! Take your box in to Screwfix and ask for a cable gland that fits, of the type shown by ahebron. They seem to do well in hiring very helpful staff who are not fazed by basic questions. The only stupid question is the one not asked, and it's extremely aggravating to order something online and find when it arrives that it's the wrong size. The threaded male part of the gland goes through the hole in the panel and is secured by the nut. The flex passes through the gland, and the acorn nut is tightened down to the external thread to clamp the flex and retain it, usually with a rubber seal for dust proofing. Crimping the wire strands is advised, with a proper ratchet crimper. I put bootlace ferrules on any stranded cable that's going into a screw retainer (like a mains plug, for instance) and use mine all the time. Screwing down onto strands will fracture them in the end. Lots of things are fine like this, but it is required by engineering standards, and it puts my mind at rest to do best practice on electrical connections. I put a piece of copper pipe around my Herald's battery cable end, that was previously loose strands going into the battery clamp. I squeezed it tight in a vice before returning it to the clamp, so the screw now compresses the pipe onto the strands, obviating fracturing. The principle is exactly the same as crimped ferrules on the ends of domestic wiring.

I'd use Colin Lindsay's suggestion, if the higher voltage is not outside normal parameters and it's awkward to adjust the regulator. I'm sure those more knowledgeable above will help if you're going to adjust the control box. I haven't got experience of dynamo cars, but I do have several integrated circuit voltage regulators in my stores that I could knock up on a piece of veroboard and put into the supply to the radio, which is what I'd do to protect it. If you are not electronically confident in making your own (components required are probably a couple of pounds in total), then there are examples like this available. The three-legged ICs take a varying voltage input and provide a regulated voltage output, up to a certain maximum current. I doubt your radio draws very much, but before going down this route it would be as well to check the figures in the manual. Use a 12V regulator and your radio will probably thank you. My partner's MGBGT has a resettable 'PolySwitch' cut-out in tandem with a battery isolation key switch for security, so with the battery disconnection switch turned off, the radio clock still functions. However, if the ignition key is turned with the battery off, the fuse blows (it resets itself) so the car cannot be started even though the battery is still connected to the radio.

Don't go down the metric route. I whip off any I find as it's a huge bind having a variety of nuts and bolts that don't match the spanner or manual. UNF, UNC etc. are readily available. I get packs of common nuts, bolts, screws and washers from fastener suppliers (some classics places offer kits for various brands, with common sizes of UNF/UNC etc. all in labelled bags) so I have no excuse for running out. Mick Dolphin is a goldmine. We also have Tim Kelly's MG garage (partner has an MGBGT) nearby and he is definitely your definition of a 'Bert' with all the parts at his fingertips. Also the elderly man in the local tyre place, who remembered the correct tyre pressures from the 1970s when putting on the MG's winter tyres! They are still around. Take care not to overtighten the clamp bolt. The faces of the clamp should be parallel, I believe, not touching or bent inwards under the force of the bolt. The distributor should resist turning by hand, but the clamp screw is not torqued up to the figure associated with the bolt size. I guess mine's finger tight then a few more flats until the distributor can't be pushed round by hand. For the MG by example, the value for a bolt-trapped design is 2-2.5lbf-ft, and 4 with the nut trapped.

Thank you. The car's been apparently fine, as it's been like this since my ownership. It was very poorly set up on purchase last year, so is now properly set with valves and timing and a new distributor from Distributor Doctor, as well as a filter-regulator to overcome the high fuel pressure even with gaskets behind the pump body. The carburettor had been overtightened so was dished on the bottom and had to be flattened back to seal to the manifold. It's been reliable, and has made it around Ireland and been my only daily car during this time, but has needed quite a lot of carburettor tweaks which I've put down to unreliable fuel pressure and probably worn carb parts. Another thread on here has suggested I check the slow running jet for the lumpiness I was experiencing just before it went up on stands to sort the handbrake, where it remains as I take the bus... As I've got it in my mind to fix things, the little filter on the breather hole is now very blackened and oily and if it doesn't even need to be there I'd rather put the original rocker cover back. It may even be in the spares that came with the car. I guess the PO decided the shiny new one was more appealing. Does the old rocker cover require a special filler cap? I seem to remember reading about one packed with gauze.

Does the handbrake lever extend too much, thus pulling the gaiter too high? I've been going round the houses to make mine work, discovering the relay lever was seized and pointing forward of the perpendicular. No wonder it didn't have any holding power even with the lever high. I understand from my research that four clicks is the reasonable maximum when adjusted properly. I need to check the slide of the rear cylinders on the backplate and the lever travel when I get the new clevis pins in the relay lever...

I think almost any kind of bizarre seal is available from the likes of Woolies Trim, Seals+Direct, Phoenix Trim and many others. I've recently bought a tub of Lanocare lanolin grease which is remarkably waterproof and not noxious like petrochemical greases. As it's safe on rubber and nice on the hands, I'd be tempted to rub some on there and at least fill the cracks a bit with something flexible and removable. Ultimately, UV degradation will destroy it. If you can see the way it seals, I'm sure even if the original seal profile is not available, something else will do. I'm trying to sort a leak in the gearbox tunnel cover and despite various 'kits' being available, all it needs is something compressible enough to fill the wonky gap. I've also had success with Seals+Direct products where they advise sticking two profiles together if you can't find exactly what you want.

I've just checked mine and it's got a crack. The ropey rubber pad Pete Lewis mentions isn't touching the boot skin at all. I think I'll take it off and weld it back together in the first instance, and pack up the pad so it doesn't flex so much. @tchiggins I expect you've a local member who can weld it back together for you? It's not a difficult job.

This thread suggests 150lbf-ft, and a means of getting there. No, I can't see a reference to that number in any of my manuals either.

Previous owner installed an alloy rocker cover with a vented cap, and a spigot by the carburettor which has a press-fit little air filter on. The angled rigid breather pipe on the cylinder block is present. Despite reading a few threads on here, I'm unsure how all this interacts, and with the additional little filter looking very oily and sorry for itself I wonder if there's a better solution.

There is a tendency for the revs to die if the accelerator is pressed when idling. My guess is over-fuelling from the accelerator pump, but there are no adjustments on the Solex B30 PSE1. The car idles well, and the engine revs once the initial hiccough has been overcome, but it does make slow speed manoeuvring tricky (especially on a hill) as it's very easy to stall by pressing the pedal too quickly. The needle valve is clear. I have attempted to address problems of fuel leaking into the manifold by adding a second shim washer under the valve, so the float hits it earlier which ought to result in an average lower level of fuel in the float chamber. With the air filter off, pressing the accelerator results in a good spritz of fuel from the accelerator pump. Otherwise, the carburettor is as normal. That comes with a caveat: there has never been a ball bearing in the accelerator pump since owning the car, despite the Solex manual showing one (part 45 in the exploded diagram in the attached PDF). Despite having had the carburettor apart a number of times, I don't understand where it could go in order to be a useful valve blocker. Any ideas? b30pse1.pdf

I can say that M5x0.8 Helicoils have been holding things down since February. The only blip has been last week when I noticed fuel leaking and found the screws had been loosened, I guess by vibration. I may have to thread-lock them.

How does the Herald wing attach to the rest of the body? Hints of rust along the wing-top of rear seams, and a sodden boot imply a PO has squirted and hoped with sealant along here, finishing off with rattle cans. Do the two come apart, and if so what's the approved method of properly sealing it, short of lead loading? I've got a 200l 3HP compressor under repair, so am hopeful of trying cellulose spraying when the weather's OK and the local bodyshop mixes a colour match. Every day's a school day, and an excuse to buy more tools...

Well, -ish Colin! 😉 Useful if the original holes were OK, but since I need to use something else for the stripped ones I'll have to hope 5x0.8 Helicoils work so that at least the major diameter is the same as the originals. Anything larger I fear might be getting a bit close to the edge of the carburettor casting. The Helicoils of that size use a tapping drill of 5.2mm so it might still be OK to return them to an M5 thread once the thickness of the insert is taken into account, as the stripped ones can have a 5mm screw pushed through but it's not loose. An alternative could be to use one of those metal epoxies to rebuild the original threads, but as the car's needed for work I don't want to risk putting the fuel system out of action while I find it doesn't work, or at least not without a spare carburettor to practise on... Glues like that seem a bit too good to be true!

Yes, it would make sense, although I can also imagine a 1950s executive retooling the licensed products for a thread common in British usage! Aren't there engines from some British car manufacturer with Whitworth heads on metric screws so they didn't have to buy new spanners for the whole company after taking over a French factory? However, I think I've solved the mystery. After a tapped M4.5x0.75 hole was obviously too small, and attempting to run an M5x0.8 die down the screw didn't work I decided it had to be an M5x0.75 thread. Which doesn't exist in the Renard scale of useful sizes, nor in any of my thread tables. However, running an online search for this on the off chance threw up a company producing M5x0.75 taps and dies, and this link for carburettor screws for Citroën 2CVs... In conclusion, whatever I do will be very awkward for a future person (or me) to identify! Maybe I'll just use M5x0.8 Helicoils and be done with it. Why they chose a thread between the standard M5 series (coarse 0.8, fine 0.5) I don't know, especially going finer than normal when it's going into alloy where stripping is a danger!

What I'd really like is to make a large board with every imaginable set of nuts and bolts mounted on it to check threads... Gauges are all right, but it's no substitute for putting a nut on a screw and finding it binds after a couple of turns! Individual go/no go gauges are mightily expensive. 34TPI doesn't exist as a thread - the used pitches are 24, 32 and 36 because they have more factors. Metric 0.75 pitch does seem to be the only answer. I've had an e-mail from the Carburettor Doctor, who says the threads are all metric. Interesting, as the screws don't fit my M4.5 die and an M5 nut is not a good fit. I'm going to try drilling and tapping an M4.5 hole in a piece of scrap.

Yes, I could go to Screwfix and get an off the shelf M5 or 6 Helicoil set but since they're available in a variety of Imperial sizes then it should be possible to get a Helicoil set of the original thread and use the 'right' screws. Like you Colin, there are also a couple of holes that have odd screws and nuts on! All well and good, but getting the nuts on with all the projecting bits of the carburettor and cables is quite the fiddle, and I don't want to take the whole thing off each time I need to check the float chamber. As there's still something funny going on with the fuelling it's been on and off a number of times this week. It's a real fuss trying to do a repair and finding the fixings one takes off are metric so don't match the parts book or the spares one has to hand! Thinking out loud, if we discount metric then it's going to be 3/16" (0.1875") or gauge 12 (0.1890") - my Presto booklet is unclear about the distinction between gauges 10 and 12. Elsewhere it appears to be 10 at 0.190". 3/16" could be BSW at 24TPI; BSF at 32TPI or "special" Unified threads at 24 to 32TPI. Gauge 12 could be NC 24TPI, NF 28TPI. Gauge 10 is approximately 2BA. Also UNC/NC 24TPI; UNF/NF 32TPI, or NS 30TPI. It can be seen in the attached picture that 24TPI BSW is far too coarse. The 34TPI of the Starrett No. 6 gauge fits well. A Metric 0.75 pitch results in...33.9TPI, bringing us back to M4.5. One can see from this table of threads that there's not anything close for the required TPI and major diameter except M4.5. Alas, the major diameter is rather too large for that! BSW at 24TPI would seem to be a much better thread for alloy than the one they used, since it's significantly coarser.

Did anyone get to the bottom of this? My Solex B30 has a couple of stripped threads and Gower and Lee suggested Helicoils. Helicoils are available in a number of Imperial threads as well as metric, so if it's possible to keep the originals it would save on head scratching later. I called Mick Dolphin today, and he has a few of the screws in stock, but is a self-confessed tyro when it comes to thread identification so can't help beyond agreeing the part number. I went through all my thread gauges and micrometer measurements of the major diameter and have not yet made a decision. The pitch is a very good match for M0.75, but the thread would then have to be M4.5 and the major diameter is almost 5mm, or about 3/16". An old Starrett gauge says 34TPI which is not a thread that exists (I wonder why they bothered to include one in the set), and while I got a reasonable result on a Whitworth gauge I haven't any of the right nuts, taps or dies to test that hypothesis. I couldn't get a good match on UNF, UNC, BA or BSF.

It does seem more sensible! Let's hope that's the case. I was looking again today as there was some persistent (though less pronounced) surging etc. I discovered the carburettor was a little loose on the manifold, so I hope that was causing enough of an air leak to create similar symptoms at light load. Tomorrow will tell... 😉

A follow up to this - I'm sorry to leave you hanging on! The short length of hose between the fuel line under the car and the pump entry was disintegrating. Bizarrely it was fine a couple of weeks previously when last checked and poked, but this time was delaminating and had incipient fissures. It's been replaced with proper hose and the problem disappeared. Since then I've put on a new Distributor Doctor distributor and leads, which means I can see the markings on the vacuum advance which were missing on the old distributor. A new job forty minutes' drive away means it needs to be reliable at least until the trains settle down. 2,000 miles since the end of September with no other major issues. I went over all the fuel lines to replace the connecting hoses and couldn't find the rubber connector that's marked as being somewhere under the car. Is this present on all examples, or could a previous owner have replaced it with a single length of rigid piping? If it's present, where exactly should I be looking for it? I've added another washer to the float valve which testing on the drive suggests has stopped the switch-off leak. Now to keep track of fuel consumption...

Yes Unkel Kunkel, the Filter King was added partly as a fuel filter. However, there is still the problem of it failing to regulate despite a new diaphragm (the Filter King was secondhand). It is either on or off with the slightest turn of the adjustment screw at the crossover point. When fuel can actually come through, there is too little thread visible for the acorn nut to fit. It's one of the things I'll look at today. As per my earlier post, I have maximum gaskets under the pump as I'm on the edge of running out of thread on the mounting screw. Pete Lewis - you recommend shortening the spring a couple of times. Does this really work? I would have thought the spring length is important to support the diaphragm, and the 'correct' spring would be the same length but a weaker spring constant. Is shortening the 'throw' the diaphragm moves through OK, without wearing the diaphragm excessively? Wagger - There's no complete starvation, but I will check this pipe. I went over all the flexible pieces between tank and carburettor earlier this year and discovered nothing untoward, but one never knows...

Thank you all. I'm revisiting this after it seemed to be OK for the last few months. Though the car was running the pressure was still too high, but a tank of fuel wasn't vanishing into thin air. The response to my new surging problems is surmised to be fuelling so I'm re-reading this thread. I spaced as much as I could behind the pump but one stud is shorter than the other and the pump can't be moved out enough before the nut can't be put on. I haven't dared attack the studs yet in case they're seized. One is not a stud at all, but a screw so there is an oil leak which I think is along this thread despite some thread lock. Tipidave - do you know which magazine the information about the washers is in? I see I can download archive magazines from the website but don't want to trawl through the whole decade if you're able to help narrow it down! The last time I had the carburettor apart the valve was working when blown through. I don't know what size the valve is. Thank you for the engine information DanMi. Wagger - the fuel was disappearing similarly to your experience. I didn't measure the consumption as it was just disappearing. A recent trip this summer after all this fettling, Cornwall to the west coast of Ireland, was in the mid-30s mpg.