This article was written by Chris Adams, © 2011 Four Ashes Garage Ltd , please do not copy without written permission. If you do not agree with this article please close the article & email us on email@example.com explaining why, we will email back with comments.
The Lagonda 2.6 & 3ltr engines are exactly the same as & so have the same problems as the equivalent Aston Martin DB2 & 2/4 engines with a few exceptions.
The cam covers on the exhaust side are different with no rev counter take off on the 2.6 & early 3 ltr engines, because the alloy water take off housing on 2.6 & early 3 ltr engines (which bolt onto the head) is different to the AM engine the exhaust cam cover is different there aswell.
Once the more usual AM thermostat housing is used on the 3ltr engines (about 1954) , our repalcement thermostat kit fits in the usual way, a full instruction leaflet comes with the kit.
It also takes the spark plugs, igntion leads & igntion parts that we sell for AM engines, with the same advice for the distributor advance, ignition timing, plug gaps being also relevant.
The exhaust manifolds, inlet manifolds, oil filler / top timing cover, carburettors, valves, cams, pistons, connecting rods, crankshaft, flywheel, flywheel housing, clutch, front cover, timing gear, etc are the same as the AM engine, however the cylinder head is 'as cast' without or little blending in the ports & so are better at producing good horsepower from these engines after the correct style of modification.
Rebuilding the engine is exactly the same as the AM / DB engines & so are the same problems & the same costs (why should they be any different).
The one big problem with the Lagonda's as far as I see it (we have had a few in now & they all suffer the same problems) is there is nowhere for the heat to escape from the engine bay, the other byproduct of reducing the heat under the bonnet is it reduces the cabin heat.
Solutions: 1st, Is to get the radiator reconditioned with a high performance core - not flushed out or flow checked - that doesn't work, never has & never will !,
or have a new radiator made in alloy which is much more efficient, this transfers more heat to the same amount of air being pushed or pulled (at or near idle speed) through the radiator
2nd, Is to make sure your thermostat is working properly, the thermostat (stat) works in 2 ways, when cold the thermostat bypass is open but the stat is closed thereby bypassing the coolant around the engine, as the engine warms the stat opens once it gets to its predetermined temperature, normally between 75° & 88° depending on climate, the stat blocks off the bypass at the same time allowing all of the coolant to flow through the radiator.
If you remove the stat without blocking the bypass pipe the coolant flow is probably about 50% through the rad & 50% around the engine only, with the rear 2 cylinders getting very hot indeed,
The original type, correct thermostat for both 2.6 & 3 ltr's is the same as a Rolls Royce & Bentley part, these are between £147 & £174 each, however we make an adaptor that easily fits in place of the original stat, this is a one off purchase which uses a Jaguar stat for an early XJ6, this is about £5 with 3 different temperatures.
3rd, Is to flush the block of all rubbish that has accumulated in the last few years, there are several products on the market to do this, be careful though as its easy to damage the delicate old alloy components on the engine / cooling system.
4th, Is to increase the efficiency of the cooling system & fit an internally shaped alloy water pump cover / fan boss, this knocks off about 10°c off the running temperature without a thermostat - so a lower setting stat will then work, say 75°c, whilst the pump cover is off make sure the impellor is only 0.015" to 0.020" from the timing cover or even better, fit one of our high performance impellors, these work better at the slower engine speeds a Lagonda engine should run at (than an AM / DB engine) as the 'blades' are shaped to pull more coolant through the engine than the STD part.
Whilst on cooling systems, Don't use one of the Performance Coolant mixes, these will damage the delicate aluminium components in the engine, which are already over 55 years old, they may also release collected debris from around the cooling system & move it into the radiator core. Just use soft or distilled water & a good quality ethylene glycol antifreeze with inhibitor & change it every 2 to 3 years giving the system a good flush at the same time.
5th, Overhaul the distributor & change the distributor advance curve for a more modern setting (less advance at upper rpm), & acurately set the ignition timing at 750 rpm idle to be about 15° BTDC & to 35° BTDC max advance at 4000 rpm, with no vacuum advance connected as this can lead to piston or valve failure.
6th, Make sure that the engine is at its peak effiency with carbs set up correctly, well balanced with no wear in the spindles, jets, needles, etc.
The fuel pump is fitted alongside the engine on earlier 2.6 & 3 ltr's, this needs a glass bowl fuel filter fitting in its place (even on the later 3ltr's) & the fuel pump moving underneath the car to avoid fuel vaporisation problems.
Make sure that the fuel supply is OK, carry out the mods to the fuel pump position as listed above, remove the fuel reserve from under the boot floor, check its condition & neither of its pipes are blocked or part blocked up, the fine filter is OK & finally whilst on the fuel system, check the tank for muck & dirt.
7th, Have the exhaust manifolds & downpipe coated in a High Perfromance heat barrier, this reduces underbonnet heat & 'in cabin' heat, there are at least 2 companies in the UK offering this, Zircotec nr Abingdon & Camcoat in Warrington.
Electric fans (often a good idea with classic cars) struggle to work as they just make the engine suffer more because the air cannot escape from the engine bay, as does fitting 3ltr fan pulleys instead of the large dia fan pulleys fitted to 2.6ltr & early 3ltr engines (abour 6" dia), however, if a solution were found to allow the heat to escape out of underbonnet an electric fan can work.
Another way at reducing the overall heat build up & getting a nicer drive is to fit an overdrive conversion, this has the effect of slowing the engine down at the most important speed range,(50 to 80 mph), i.e: at 70 mph (3600 rpm) the engine would produce a fair amount of heat, with the overdrive engaged this would be down to 2800 rpm & so less heat making it less fussy & more relaxed (& more economical) at modern driving speeds - This also has the effect of reducing the cabin heat as the exhaust system, underbonnet heat & gearbox heat will all be reduced.
To Be Continued