Engine tuning

I had setup the engine well enough to start and tick over but I could tell it wasn’t really happy as it seemed to splutter above 1500rpm. Cutting a long story short, I had to reach out to the VSCC boys for some guidance as I *thought* I had set everything up as per the factory settings. I also discovered that water was leaking into the inlet manifold which means that it was mixing with the fuel as it was sucked into the combustion chamber – not ideal. This meant that the fuel/air mixture was severely weakened and that turned the exhaust pipe blue because the gasses were excessively  hot.

Resolving the water leak required the carburetors and manifold to be removed, the issue(s) fixed then everything reinstalled. The ignition timing it turns out was setup totally incorrectly. To enable vintage cars to start, the driver used to manually adjust the distributor so that power was sent to the appropriate spark plug when the piston was at the absolute top of its cycle. Then once started it was adjusted so that the spark plug started to fire around 8 degrees before the top of the cycle (which allows time for the spark to fully ignite the fuel). The factory information doesnt mention how to configure the ‘engine running’ setting and I was leaving it at the ‘starting’ position. It turns out that this okay to start the engine but to obtain driving power its an order of magnitude out. The nice boys at the VSCC advised me to simply move the distributor when the engine was running so that it performed smoothly and then to lock it into that position instead. So thats what I have now done until the car can be driven on the road and more accurately tuned. It has completely changed the sound of the exhaust interestingly – it is no quieter just a lot smoother.

The brake shoes have been sent off for new friction material to be fitted and I await their return.

Below are a few pictures of the car as-is as I think many people have not seen how the car currently looks. There is a long way to go but it definitely looks like a car… I have since polished the blue out of the exhaust manifold…




Fuel things

Today I was going to look at the charging system but changed my mind and instead focused on the fuel side of life. The petrol tank was custom made when the body was crafted and it mimics the original tank in looks but aside from that it is unique being made from aluminum with a few customisations. The fuel sender is a marine item whereby the fuel level in the tank is measured by a bobbin that floats up a vertical sensor shaft. Realistically, there are no moving parts to the sender as the bobbin is not actually attached to anything – the shaft senses where the bobbin is and sends a specific resistance down the sensor wire to the gauge within the range 0-180 ohms (0 being empty). Trouble is vintage fuel gauges had totally different resistance ranges and in all the spares I had the range was 250-0 ohms. Completely opposite in functionality. For a while therefore I am forced to use a modern alternative which sort of looks alright but sadly not really what i want… hey-ho I need to know the fuel level so this is put back on the job list for another day. On the positive side I know that this part of the new wiring does actually work.

My other non period customisation is to insert an inline fuel filter as a just-in-case. The tank may have tiny pieces of aluminium dust still inside which would not be great inside the combustion  chamber and it also gives me a visual that fuel is actively being pulled from the tank to the engine.

Below is the engine bay with the newly provided fuel system. It finally looks like a proper vintage racing engine. One day I will get round to polishing both the rocker covers on the top of the engine.

I may remake the copper pipe that runs from the petrol pump (top left) down to the first carburetor – I think I can improve on the route and I sense the 360 loop is not actually necessary. Sadly whilst I am making huge strides forwards I do have a few issues to resolve:

  • Cylinder 3 is noticeably running hotter than the other cylinders (really weird)
  • The rear carburetor has a slight fuel leak (which may account for the above issue)
  • There doesn’t appear to be any oil getting to the inlet valve rocker shaft

I also took a look at the fuel/air mixture and I found the front carburetor was set too rich so I spent a happy hour ensuring the fuel levels were the same in both carburetors. That will make a difference to the tuning and it also meant I had to remake the mechanical choke connections because the length of the original ones were too short resulting in their enriching the front carburetor without my knowing. This is all resolved now.

All of the technical issues need to be addressed before the car can be driven – oh…. and I need to rebuild the entire braking system which had slipped my mind for a while 🙂

We are getting ever closer to driving the car after which I fully expect to unearth a whole host of other challenges….

Wiring and firing

Most of the day was consumed working out how to run the wiring from the new fuse panel under the dashboard to the various components that required power.

First priority is the brake lights. I definitely need those before I take the car on the road but because of the cars age, the UK laws mean I am not required to have any other lights or indicators fitted or working as long as I do not use the car in the dark. To be honest I will fit night lights and indicators later as other drivers are used to seeing them but the point is that I don’t *HAVE* to fit them to be road legal if I use the car in daylight.

Rolling under the car, I could see the remains of the brake light switch. Naturally, it was seized solid but I had purchased a replacement a long time back envisaging that if the switch still existed, it was likely to be un-salvageable. Engineering wise the switch is very basic and is operated by the brake rods ‘pulling’ on a spring which is connected to the ‘switch’. When the spring is under sufficient tension, it pulls the two connections together within the switch. What I didn’t know initially was how much tension was needed to make it operate and how much physical movement was required to obtain said tension. But I did at least had a working start point. The old switch was unbolted from the chassis and found to be riveted to a mounting plate which is not supplied with the new switch. So carefully drilling out the rivets to preserve the mounting plate, I transferred the new one into position and locked everything into place with small stainless steel screws.

The mechanics of all this are the easy part. The tricky bit is manufacturing a wiring loom. Running cables underneath the car means they are exposed to the elements and somehow all the individual wires would need to be covered in a single protective material. I therefore decided that I would cheat and take advantage of a multi-core cable designed for use with a trailer/caravan. This is a heavy duty 8 wire cable to safely provide driving lights (and charging) on a caravan and more importantly it is pretty cheap to buy as I only need about three meters. I worked out a route for the cable to follow then considered future wiring needs (night lights, indicators etc) specifically leaving myself sufficient lengths of wire for that purpose.

The brake and rear lights you will remember are now built into a removable panel that mounts in front of the two spare tires. Basically I needed to extend the cable from the chassis rail out to the lighting panel leaving myself enough free cable for the lighting panel to be removed whenever I need access to the spare wheels. You may note that the cable is run to the panel through flexible stainless steel tube (like a small scale shower hose). This is a period accessory on luxury cars back in the day so I thought I would add a little luxury to the car even if this is the only bit.

The main multi-core cable is  fixed to the underside of the floor safely against the chassis rail. All the wiring is routed down one side of the car and the fuel is routed down the other side as I thought I might as well keep them separate. I did consider fixing the cables permanently to the chassis rails so that I had the future option of removing the floor boards, but I cant think of an occasion where I would ever need to do that. Once the cable was routed I simply applied 12 volts to the appropriate wires to check everything worked before locking it all into place. The brake switch spring fitment did need some adjustment in order for the lights to come on when the brake pedal is slightly depressed but this was not difficult to achieve. The key part is that I now have working brake lights.

More exciting was refitting the newly machined exhaust manifold which I am pleased to say now nicely seals against the cylinder head. The radiator was refilled with water to double check there were no leaks (I have one small leak to fix) before I refill it with Fernox and a temporary fuel feed was provided to the carburetors as the real feed from the fuel tank is not quite finished yet. The engine started on the button (which still surprises me) and ticked over at 1000 rpm (way too high) so I connected my strobe tuning light and pointed it at my previously manufactured tuning disc…  Aha! The timing is around 3 degrees out so the distributor was rotated until the strobe flashed when the rotating disc was immediately below the pointer. SUCCESS!!! My removable timing device does its job perfectly and is sooo much more accurate than guessing where top dead center is. With this adjustment the engine speed  dropped to 700rpm but it is supposed to be between 350-400rpm.

I then noticed that both carburetors were partly operated at idle so it was a thing of moments to loosen the brass linkages allowing the carburetors to return to their natural closed position. I then tried to start the car but it refused to play. I wasn’t quite sure why but knew the engine started before I closed the throttles. Opening both throttles very slightly resulted, I guess, in the engine being no longer being starved of fuel and air allowing it to fire up and immediately settled into ticking over at 200rpm. That was a surprise as I have never had a car that could tick over that slowly but I am told there a whole bunch of vintage engines that run slower than that.

Using my 1960’s “Crypton Synchro Check” balancer I adjusted both carburetors to have the same air flow rate increasing it slowly until I achieved the desired tickover speed. I still need to get the fuel/air mixture right, which will require further adjustment of the air flow but to ascertain the right mixture – I have to drive the car (wow how exciting is that thought).

The picture below shows my trusty ol’ Crypton then below that tool in position but the  the engine is not actually running in the picture – the dial showed 3.5 on both carburetors when it was ticking over.

One final picture to show the engine ticking over around 400rpm, reasonable oil pressure at idle (45psi at 1000rpm) and the water temperature coming up. Its in Fahrenheit (which is not very British) and ‘boiling’ is of course 212F. For me a gauge that reads 100C as a maximum makes far more sense. I will replace the oil pressure gauge at some point as it will never read more than 50psi so its pretty pointless having a gauge reading up to 160 psi. I believe this one is for a Riley 9.

Next ‘essential’ job is I think wiring up the dynamo/regulator etc so that the engine charges the battery whilst driving… poop poop.

Petrol tank protection

The fuel tank sits out in the open in between the chassis rails just behind the rear axle and is also close to the rear wheels. It is therefore at risk of damage from stones being kicked up by the rear wheels into the sides of the aluminium tank. The tank itself is constructed from 3mm aluminium but a bit of protection won’t go amiss.

Vintage Bentley’s placed a strong mesh on the sides of their fuel tank so I am using their concept. When I had the tank made early last year, I already had this idea in mind and asked for mounting tabs to be built in. Conceptually the mesh would have a frame that wraps around the edges of the mesh. I tried bending a U channel out of sheet steel but just couldn’t produce anything I liked the look of. Next idea was using aluminium U channel and bending it to shape. I discovered that I can’t bend U channel and was forced to form it using straight lines. This took a couple of hours but sadly again I was not happy with the aesthetics. I grant you people are unlikely to notice the mesh but that’s not the point.

Next theory: the stainless steel mesh is pretty strong and doesn’t really need a frame so I tried it against the tank ‘naked’ and placed some shaped washers onto the mounting points. This looked far more elegant and is my current solution. The fuel tank and the mesh will sprayed body colour so the whole thing will be quite subtle.

To ‘complete’ the fuel tank, I turned my attention to the drain plug which needed to be drilled to allow locking wire to be fitted. The locking wire simply prevents the drain plug from coming undone by accident. This is a racing requirement.

The fuel tank is now ready to be refitted and a pipe fabricated running into the engine bay. Something for another day seeing as it’s -5 outside the garage at the moment.

Battery location

I have been considering where to mount the battery for months. It makes sense to install it close to the engine due to the voltage dropping as it travels down the cable and you need all the power you can get for the starter motor. Problem is that most of the weight of the car is at the front due to the engine and gearbox location, the rear wheels are pretty much only held down by the weight of the chassis and rear axle. It is therefore extremely likely that the rear wheels will want to lock up under braking.

Ok then lets put some weight over the rear axle then. You may recall my mounting two spare wheels right at the back of the car, they do not weigh a huge amount but it all helps. So what I now want to do is install a battery box under the rear seat, right in front of the axle. Ah, one of the shock absorbers is in the way as is the brake rod. But if I mount the battery anywhere else, it will be too low which is bad for playing in the mud. Eureka moment – if I take out all of the wood behind the front seats, I can pop the battery box roughly into place. As you can see there is not much room. Granted I could have a smaller battery box but I want the ‘option’ of being able to fit a bigger batter in case I need it.

I then put all the wood back, crawled under the car to move the box about and marked the wood accordingly being careful to observe the potential movement of the rear axle.

Below you can see the wood back in place. This is 20mm marine plywood and is pretty strong, but I know that I will have people in the back of the car bouncing up and down in an attempt to get the rear wheels to grip in wet mud so I want to add a strengthening brace just behind the battery box. The round hole is so that I can gain access to the rear axle as the oil will need changing at some point and the petrol tank will prevent access otherwise. The strengthening brace is 30mm angle iron securely bolted to the wood from underneath.

In the picture below, the steel strengthening brace has been installed (but you will never see it). But you can see that the wood has been protected against moisture with all fresh cuts stained to match the rest of the wood. The temporary cross head screws have been replaced with more period looking Stainless Steel slot head machine screws and the electrical cables have been run in too. The earth cable is very short in length whereas the positive cable has to run all the way to the front of the car so that is almost twice the size to minimise the voltage drop. The battery terminals are not yet fitted but they use a bolt on fitting to suit the cable ends.

The backseat can now start to be built up with a panel the backrest cushion will mount onto made from 20mm marine ply. This will be cut to match the shape of the rear of the car and gains me a handy storage area behind the seat. The seat base will spread the load across the panel the battery is fitted into serving a double purpose.  The piece of wood shown is too small and does not reach the sides of the car but you get the idea.

Exhaust wrapping

You will know the exhaust pipe runs along the outside of the car and it will get hot. Potentially very hot. Anyone sitting in the back has a seriously real chance of leaning their arm on the exhaust pipe which I imagine would not be popular. Also entry into the car will be stepping in over the exhaust – more opportunities to warm up body parts. The answer is to wrap the exhaust pipe with a protective layer. Historically people used asbestos rope simply wound around the pipes but I have gone for exhaust wrapping tape which although not exactly period in manufacture – its much safer. Time will tell if the VSCC scrutineers dont like it and make me revert to something more period. You may have noticed it in the picture above but this is the whole pipe

A good days work… 

Exhaust Manifold

The 4 branch stainless steel exhaust manifold was custom built for the car but unfortunately the flange that bolts the manifold to the cylinder head had warped during construction and despite all attempts it refused to seal in the gasses on cylinder number two.

In my heart I knew there was only really one answer – I need heavy duty machinery to re-surface the face so that it becomes absolutely flat and true. That is something I cant do because it requires a large milling machine. Luckily I have a friend who teaches and runs the machine shop at a local university.  Liking a challenge outside of normal education, he took the manifold away to work out how to clamp the unwieldy item securely and more importantly – square. The challenge achieved – all it took then was to let the industrial milling machine do its job. Given that the material is stainless steel (which is very hard) – I rather imagine it took some time but it came back looking nice and flat. I now had a smile on my face and a nice bottle of Premier Cru swapping hands in trade meant we were both happy.

The manifold sits noticeably better against the cylinder head which has to make a difference. Now to re-order some replacement gaskets – funnily enough I have run out…

Bonnet Support & Ignition

The bonnet as constructed by the coach-builder fits as it should with the standard radiator cap. Naturally ‘standard’ doesn’t fit in my car building world and I had upgraded it to a sporting quick release filler as you may recall. Problem is that the bonnet when opened fully slightly hits and then slides down the side of my nice aluminum filler cap. Up until now my solution to this has been a short length of oak doweling cut to size which I manually insert between the two pieces of folding bonnet so that the top section is lifted clear of the filler cap. This is fine as far as it goes, but I thought I would machine  a more permanent support.

Essentially my solution is a length of brass rod machined to have a load spreading brass washer and tapped to have a securing ‘bolt’ inserted into it through the bonnet. A securing bolt is obviously not aesthetically pleasing so I machined a slim circular ‘bolt’ to take over that role. This is fairly wide and matches the washer on the other side (load spreading). I am happy with the solution to the point where I had forgotten I had made this and simply open the bonnet now. This post is therefore a slight catch-up.

The view from the outside. It will almost certainly be painted along with the bodywork.

…and the view of the support inside the bonnet. It is so subtle. I dont think anyone will ever notice it. All I need to do to finish this off is fit a rubber (or maybe cork) pad to the bottom of the brass support so that it doesnt wear on the hinge. You can see that it misses the radiator cap quite nicely now.

Ignition timing

Up until now the ignition timing has been a complete guess, there are no timing marks whatsoever, the manual merely advises to  set the ignition to fire at zero degrees before the piston is at top dead center (TDC) of its motion. TDC I can locate, having the ignition fire at exactly that moment is impossible to work out. So I constructed a removable timing tool that when using a strobe light (it flashes a light at the same time the spark plug fires) I should now be able to set the timing accurately. I do of course need to have the engine running to do that which I cant do at the moment as I have given the exhaust manifold to a friend to machine flat which will prevent the exhaust gasses on cylinder 2 escaping.

Having converted the engine to have a water pump, I lost the ability to have an engine driven fan because the pipe work is in the way of the pulley location. Taking advantage of the pulley mounting I fabricated a tube to extend the mounting forwards past the offending pipework. Onto the face of this tube is fixed a disc that will rotate once every revolution of the engine. I then carefully set the engine at top dead center for Cylinder 1 and fabricated a ‘pointer’ to provide an indicator above the disc. Marking the disc with a silver line where the pointer happened to be means that now when the mark on the disc is rotated by the engine and it aligns with the pointer – the engine is at TDC. Simples. So in theory when I next start the engine I can use the tuning Strobe light to check the setting of the distributor by pointing it  at the mark on the disk. Adjustment of the Distributor position means that now the timing can be advanced or retarded until the strobe flashes at exactly the moment the mark on the disk is directly below the pointer.

Once the ignition is set I can easily remove my new ‘ timing tool’ but repeat the exercise if I ever need to. Nice. Looking forward to having the engine running again.

Below you can see the timing disk and the pointer with the ‘timing mark’ visible below the pointer. Both the disk and the pointer are easily removable but will always mount in the same position again.