Hullo David, from some recent experience assisting a colleague, and working on my brother’s from many decades ago, my suggestion is as follows:
1 - Remove carburettor complete. A few cautions - take care when releasing the fuel pipe banjo bolt. If you have not released or tightened this before, you won’t know how tight it is, and it may be over-tight, or seem so from a long time of non-disturbance. To prevent twisting of the float bowl cap and the risk of breaking something, you need to provide a temporary reaction by other means. I try to grip the banjo spigot and pipe with something like a snug fitting adjustable or open-end spanner, and done carefully to avoid bruising or scarring, and holding it in line with the pipe. Disconnect the accelerator arm and the choke cable at the carb. Make sure you don’t lose any special connectors.
(P.S. Is that top cable a hand throttle control? If so, that was not standard and it looks like an odd close adjustment setting. I can see the choke cable deep down so it is something else.)
2 - Remove heater hose at the rear, followed by the connector.which is easier to do whilst on the car. (After draining the water, of course.)
3 - Remove the thermostat housing, but remove the temperature sensor bulb first for protection.
4 - Remove water manifold. Now you are going to enjoy some of the annoyances of these cars. The manifold must be removed horizontally, and simultaneously from the 4 studs for the intake chamber and the 6 studs on the water jacket elbows. The configuration of these nuts is such that they are very snuggley fitted against their adjacent castings. It is virtually impossible to fit a 12-facet socket or ring spanner, both of which would give helpful fractional rotation. You really need to resort to an open-ended spanner and hope you can get sufficient rotation to release them. It can be slow and tedious and worsened by the threads which are usually tight from age and black steel. One can see that tube spanners were a general tool in those days before interchangeable sockets became normal. You may find a tube spanner will fit, but often there is not a straight approach available either.
With all nuts removed, you need to carefully crack the gaskets apart by working equally at as many places as you can access. Many use a screwdriver, which burrs the casting edges, but a strong paint scraper driven down into the gasket is neater. The main care is to avoid too much twisting of the casting from the vertical or parallel as it is easy to break a lug.
5 - Reassembly is the cliche’d ‘reverse order’ but there are several things to make life easier for this stage.
- Check for excess corrosion around the water passages. This is a major problem and I have several manifolds ready for scrap. Electrolysis has taken its toll after 70 years and the aluminium is the sacrificial lamb, with the iron being the culprit. (Cars have always been built for an economic life, not an engineering perpetual life.) You will notice that the major corrosion is in the immediate vicinity of the connection with its associated iron component, but it will extend throughout. My colleague has a pinhole leak in the top of one of the three arms of the jacket and for now, it will be repaired with an epoxy product. Consider having some welding done where serious, to build up around corroded edges before they get too thin.
- Run all threads with a die nut and tap for all studs, bolts, and nuts and check that they are all free-running.
- Clean all gasket surfaces thoroughly and dress the faces to show enough bright metal to confirm you are at ‘ground zero’.
- Check that the faces of all five flanges are in the same plane. Refacing would probably be recommended if this is more than say a few thou.
- Make sure you use the same thickness of gasket for all five flanges.
- The heater offtake is a BSP parallel thread and only a parallel thread fitting should be used (with a sealing washer on the face of the casting), as it is easy to over-tighten a tapered fitting and crack the aluminium. (I have one such repair to do, caused by someone not knowing what they were doing.)
- check for any other works you should do whilst you have access to this side of the engine e.g. starter; core plugs; cleaning and degreasing everything; repainting engine; exhaust pipe and manifold rejuvenation; etc. It is very easy to turn a one-week job into a four+ but these extra works would not usually get done unless you had to dismantle something at another time and they do make the under-bonnet area look extra attractive.
- Tightening to a specific torque is not something usually applied to these for a few reasons - none are dependent upon a critical tension, it is tightening a basic soft-metal aluminium, and you cannot fit a conventional torque wrench onto them. It is usually tightened by hand to a good ‘feel’ from experience, and equal on all ten. It is not a pressurised system so good gaskets and mating faces will do the job. I usually run a small ring of gasket sealer around the water hole in the gasket where a leak could occur but not all over as it makes it much more difficult to separate later.
- Spring washers should not be used against the aluminium, and it was usual to use flat washers only.
Just one note of warning. Take care, as I am not aware where you could find a decent replacement and I don’t know of anyone casting new ones. They are weaker in critical areas at flanges due to corrosion. Alan Gibbons (SS Jaguar club) in the UK has made a few for the 3.5 but he said there has not been a call for the 1.5, despite these being the most common model.
I don’t think I left anything out, so good luck. Other readers may have further information from their experiences.
