WRITERS’ ROVERS
Alisdair loves tinkering with his cars, but there’s one skill he’s struggled with...
TINKERING WITH our cars is, for many, one of the great draws of owning a Land Rover. Easy to spanner, understand and fix, few cars are more Diy-friendly than our beloved Land Rovers. However, of all the fettling jobs on my cars, there’s only one item I don’t feel I’ve quite nailed; the slightly rich running of my Series I.
As soon as we got the engine turning over, it would start brilliantly, idled well,
but bogged down on rapid acceleration, and seemed to run a little rich. Not smoking like a Red Arrow, you understand just a faint dark tinge to the exhaust output. The first job was to overhaul the Solex carb, which James and I did with a full Solex kit, including new jets, washers, needle valve, gaskets, spindle, butterfly and accelerator pump diaphragms. All was well, it started and ticked over beautifully, but the bogging down and rich exhaust issues were still there.
There isn’t much to set on a Solex, just idle speed, and the volume mixture screw, which allows air into the mix, and the choke arm. Looking online, the base setting for the carb was one and a half or two turns out on the volume mixture screw. At that, mine would just run so lean as to start popping and spitting back up the carb. Mine ended up running at best barely half a turn out on the mixture screw, and the choke arm set at almost 1 o’clock, looking from the nearside. I’m on new coil, new plugs, leads, distributor and a Powerspark ignition system rather than points, and compression is excellent on the 26,000 mile unit.
Whilst rebuilding the car, we later timed it bang-on with a strobe into the flywheel cover, including the vacuum advance on revving it, and it ran better, but still a little
rich. This was how it was left for a few months. My splattered garage wall said it was definitely rich (see picture above) but a long run revealed about 16.6 miles to the gallon, so I looked into it all again, as it should do 18-25. I’m ignoring 25, but would hope for 19-21 mpg.
Solex exploded diagrams showed a single fibre washer under the needle valve; mine had four on. I also noticed the choke arm on other cars was typically set at about 10 O’clock, lining up with a screw on the carb body, whereas mine was set much richer, almost vertical. Four washers would, in effect lower the float height, affecting the delivery in the emulsion tube. Reset with one washer, trying both the new needle valve and the (not that worn) original allowed the choke lever to be moved nearer its assumed correct, more forward position, around 11 O’clock. Removing the accelerating bog-down issue by adjusting the choke arm towards the bulkhead gave a little black smoke at idle, but now without splattering the garage wall; tweaking the choke arm forward (leaning the mixture) gave a clean exhaust, but horrific bog-down and then stall on heavy acceleration.
Carb tuning using the usual trick of raising the idle up, then adjusting the volume screw in and out to find the rich and lean hunting spots and settling between them didn’t seem to do anything, annoyingly. The throttle spindle doesn’t have excessive wear, so I’ve ruled out air leaks there, and have checked for air leaks on all inlet joints.
Frustrated, I researched more, and now believe I’ve nailed it down to the accelerator pump action. A manual tug on the pump arm shoots a huge squirt into the carb, but on revving a running car, though the spindle cam and accelerator rod moves, the pump arm barely moves at all. I reasoned the setting over the pump acton may be the issue, the bogdown being not enough fuel pumped in; the black smoke meaning a fraction too much. The rod and cam can wear horrifically, which would effectively lean the pump action, but stripping the cam and rod showed no keyhole on the cam, and only the faintest wear to the rod.
So I’m now experimenting with washers on the pump rod, effectively tweaking the action of the pump arm minutely, where there should be .030 inch clearance. The next hole richer on the arm is too much, so I’m on the middle hole again, which has allowed two changes; I’m right forward with the choke arm, level with my assumed correct position by a screw on the carb, and am finally a turn and a half out on the volume mixture screw, something I’ve never managed before.
I need to give it a 50 mile run to check consumption on these settings, but the plugs are nice and white after a run, so the mixture is on the lean side of correct, but can I eliminate the weak black smoke?
At Land Rover Legends, Philip Bashall was dismissive of it as an issue, blaming modern fuel and pointing out my car hadn’t run for nearly two decades. There’s a well-respected, old-school carb specialist nearby, but I’m slightly loathed to spend on getting him here potentially to be told ‘they all do that’ as he takes my money.
As someone who likes his cars running at their best, this is annoying me. If you know the secret, possible settings, have a suggestion – or can set it up – do contact me: alisdair@ alisdaircusick.com.