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Aston Martin DB2 to DB2/4 MkII's were fitted with the W.O.Bentley designed Lagonda six cylinder, twin overhead cam engine, after David Brown bought Aston Martin he then bought Lagonda for this engine.
The VB6 series engine was made in 2 capacities, 2580cc in the DB2 & early DB2/4's, then 2922cc in DB2/4 DHC's from April 1954, Saloon's from August 1954.
Note: the 2.6ltr block cannot be bored out to fit 2.9ltr liners, the 2.9ltr block is strengthened in the lower liner bore area & the sump flange, the lower liner bores on a 2.6ltr are not spaced correctly to move the liners acrossfor the 2.5mm offset. The largest bore that can be carried out on a 2.6ltr liner* & fitted to the std block reliably is 80.5mm, this gives 2.75ltrs.
The engine detailed design was carried out by Willie Watson under the guidance of W.O.Bentley, the engine had a 78mm bore with a 90mm stroke at 1st then Eberan Von Eberhorst re-designed the engine to take larger bored liners of 83mm for the DB3 sports racing car.
The crankcase was of a cast iron 'barrel' type, wet liner design with 3 round cast light alloy 'cheeses' which bolted around a 4 main bearing crankshaft, the (rear 3) cheeses housed shell type main bearings, the crankshaft was a fairly advanced part counterbalanced design with a thin scroll seal & thrower ring at the rear of the engine, this crank was fitted in from the rear of the crankcase & passed through the crankcase to the 'intregral to the block' front main bearing housing, the big end journals (bearing) were originally white metal direct into the connecting rod, soon changed to shell bearings fitted into the rods, pistons were a light alloy 6.5:1 compression ratio 4 ring design. The pressed tin sump was filled with 14 or so pints of oil which was then circulated by a twin 'vane' gear type pump of adequate proportions, bearings & head were fed through an Autoclean type filter (this had a handle you turned periodically cleaned out the sludge !) with adaptor shortly to be replaced by a Purolator replaceable element filter mounted on the same adaptor. The original STD DB2 2.6ltr blocks & heads were painted dark to mid grey, alloy front & rear castings were left as cast, its debateable whether the cam covers were polished to the high standard of today.
The cylinder head was also cast iron fitted with water cooled chilled cast iron valve guides, replaceable valve seats, 1.515" inlet valves, 1.365" exhaust valves, thimble type nominal 1.5" dia cam followers, 0.345" cam lift on both cams, the cams being driven by a long top 104 link timing chain which was changed to a 84 link with a revision of the chain adjuster, this resulted in an engine which was less noisy & thrashy at rpm above 3000, the timing case was a light alloy casting which also housed the chain driven water pump.
This 'in built' water pump was fairly troublesome with coolant leaks from the gland seal into the cavity around it which then leaked from the 'relief' hole bored in the side of the front cover behind the coil which people then blocked up then often causing water in the oil (emulsion), then blaming the head gasket (which also could be troublesome), the timing cover also held the front engine mounting & twin stabilisers either side of the centre mounting.
The inlet manifolds were of cast light alloy & water heated, the exhaust manifolds cast iron with cup type fittings to the exhaust downpipe.
The DB2 was 1st equipped with 2 x 1.5" H4 SU carburettors, with 6.5:1 compression ratio it gave 105bhp, power was soon boosted to 125bhp by virtue of 2 x 1.75 H6 SU carburettors, an exhaust cam with more duration, an increase in compression ratio to 8.2:1, this was then called the DB2 Vantage engine (the 1st time the company used the 'Vantage' name). It was also fitted to the 1st versions of the DB2/4 without major alterations (without the use of the 'Vantage' name
The block & head (cast iron parts) are painted 'almost' pillar box red, in fact David Brown hunting pink, again front & rear alloy casting remained 'as cast'
The next increase in power was by increasing the bore of the engine to 83mm, this was achieved by offsetting each pair of bores 2.5mm away from each other (this offset was to remain with the later DB series engines of the last 'Feltham' built cars) giving 2922cc, with the exhaust cam profile being also fitted to the inlet side it gave 140bhp. This engine was the std engine for the DB2/4 from 1954 on, it was painted the same red as the earlier engine.
The DB2/4 MkII was also equipped with this engine, the company then offered an uprated engine with larger 1.725" inlet & 1.625" exhaust valves called an L1 option, this gave 165bhp. This was reputedly too use up scrapped std head castings & didn't use replaceable valve seats, several DB2/4 MkI's (retrospectively called after the MkII was introduced) have been fitted fitted with this head by the service dept after manufacture.
The engine has been sorted out from the poor reputation for reliability into a reliable long lasting performer (this is when rebuilt by ourselves, we cannot vouch for other engine re- builders / restoration companies)
Once the bottom end has been sorted out from poor oil pressure, oil feed & oil leak problems, the poor quality STD pistons, liners, connecting rods must be replaced to avoid very much larger bills when these fail, with the head receiving new bronze guides & unleaded seats amongst other things to sort that out.
The unit responds well to cylinder head porting, valve & cam improvements, the twin 1.75" SU carbs (4 bolt flanges) fitted to all engines after the 1st DB2 non Vantage engines (1.5" SUs with 2 bolt flanges) are adequate up to over 200bhp on a 3ltr after improvements in exhaust manifolds, etc. If much horsepower over 200 hp is required a new block is needed. - The old one walks & you can't keep a head gasket on it. !
If using a 2.6ltr unit for any form of power upgrade from 125 bhp it will need a block sump flange strengthening plate as the 2.6 ltr block has a 1/16th (0.0625") thinner sump flange than the 3ltr, this allows the block to flex, eventually damaging the crank, fitting this plate to a 3ltr after any tuning isn't such a bad idea either.
We supply a great many unique improvements, both aesthetic & practical to maximise your pleasure & enjoyment of these fine engines, here are some of those parts/
More on Engines can be found here
About MkIII DBA, DBB, DBD & DBC engines here