Straight (six) talking
Q
My 1973 Land Rover forward control fire engine is fitted with the original 2.6 straight-six petrol engine. Apart from carb overhaul and electric ignition kits, I’m finding it impossible to source information on improving the engine. Do you know of ways of bettering the power and torque output?
Vernon Steel, via email
Martin says: A
Tuning options for your engine are limited, and because the 2.6 uses a different bellhousing to the 2.25, it’s not quite so simple to drop in a V8, Tdi or 2.5 diesel, as with other models.
The most surprising power gains, however, are often made by sorting out decades’ worth of misunderstandings by previous owners and mechanics – for example, incorrect valve timing; valve clearances too loose or too tight; wrong ignition timing; seized advance mechanisms in the distributor; failing condenser, floppy contact breakers and/ or baseplate; vacuum leaks; loose, bent or damaged mounting flanges on carburettor; wrong carb float level; insufficient fuel delivery due to a flagging pump, clogged tank pickup, perished or loose fuel hoses pulling in air… we could go on.
Having fixed this backcatalogue of ignorance and neglect, and then tuned the carburettor(s) correctly, you can consider a few more involved operations. Remove the head, lap all the valves in to ensure perfect sealing and remove all carbon deposits.
Consider having the ports gasflowed (a job for someone experienced, whatever Youtube says) and having the head skimmed to raise the compression ratio – but make sure it wasn’t made for five-star petrol in the first place or you’ll make it worse. If the exhaust manifold is an unhelpful shape, you could commission a tubular manifold and downpipe. Such improvements may have a knock-on effect, however, leading to an ongoing rolling project.