My ‘73 petrol Land Rover Series 3 has been having stalling issues. It will seem to be tuned properly, running great, but at about 15 minutes into most test drives it will stall out. Usually at a stop sign. Then it will not start up until it sits for 5 minutes or so. It’ll have a stale air or faint burn smell when I pop the bonnet (not a fuel flood smell) - can’t tell from where. It will start up after waiting, with lots of cranks and gas. It’ll get me back home and runs great at high speeds but it will stall again, sometimes during slow driving. I would appreciate any suggestions. I’m stubbornly trying to fix it myself, but I’m about ready to take it to a pro mechanic. (any suggestions in San Diego area? I've called around and many won't take on old Rovers anymore). Please tell me if I’m missing something really basic. Pardon the lengthy details. Until this, it was running solid for 25 years. Including many middle-of-nowhere Baja runs with no troubles.

Perhaps describing the first stall could give indication... After a common 30 minute freeway drive it backfired big upon deceleration off the freeway, then went a mile before the first of the now familiar/frustrating stalls.

First suspect was fuel. It is getting good flow, but I replaced the fuel pump anyway. Flushed the tank (no rust), checked for clogs. Then rebuilt the 15 year old genuine Zenith. Did the flattening trick in case of warping. Seems clean and functioning. Still had the stalling. Bought a new RN ‘replacement’ Zenith. No difference. New fuel line and filter, at proper angle ( to avoid vapor lock). During a gasping stall while moving at about 10 mph, a cyclist was along side and he stopped to say it sounded like it was fuel starved. I think I’ve tried every mixture variation (lean/rich), but usually stay near the specs - following the carb plaque by the radiator.

Second suspect was ignition. It was running a Pertronix reliably for 10 years with a Lucas coil. Reverted back to new points for a day just for giggles but it did not help. Tried a new Accuspark distributor with a new coil. Still stalled. Now a new Pertronix distributor which seems to run good with a new Lucas DLB101 coil. (maybe still a coil issue?).

Third suspect was for exhaust leak. Did a smoke test and saw no leaks but a mechanic friend told me to replace the gaskets anyway, so I did all from carb to manifolds to engine. Installed a new brake booster (fun times!). A vacuum gauge placed at the manifold pipe going to the booster shows a steady needle.

It had an engine rebuild a few years ago. Compression is even - about 115 in all four (on a home test gauge). Valve clearances are triple checked and perfect. Timing is set TDC, trying slight variances A-B. Rotor points to plug 1 when TDC. New plugs and wires. It still has the stock air filter, PCV valve (new diaphragm), and stock Cooper fume vent and breathers, etc. Replaced the head gasket a year or so ago. The exhaust and muffler are clear - unclogged.

A couple of neighbor veteran car guys have had a go at tuning it. They’ll say the engine sounds really good and strong. They’ll set the carb confidently their way. It seemed perfect again but sure as heck it stalls later on the test drives. Making carb adjustments during the return doesn’t help. Even in the driveway, I'll set the idle steady at 750, but the rpm will suddenly drop to 400 or so, or stall with a tough re-start. Maybe a bad electrical ground? Maybe some sort of vapor lock with the fuel tank/vapor tubes? It has a new vented fuel filler cap.

Any guess is appreciated! Cheers, Ty