[alfa] Alfa 6 - carbs

["John Hertzman" <johnhertzman@xxxxxxxxxxxxx>]

The discussion about the Alfa Sei carburettors started very innocently with a precisely stated question by Hans Milo ("I'm looking for a pair of 3.0 V6 carbureted heads, in rebuildable condition. A couple of hundred GTV6s were sold in South Africa about twenty years ago with 3.0 engines and carburetors") and a perhaps less careful response by George Graves ("The original Alfa-Six saloon also had carburettors (six single throat Del'Ortos as I recall). It might be easier to find one of those manifolds than it would be to find a manifold from a South African 3.0 liter GTV-6. BTW, you are aware that the S.A. 3.0 liter was a different engine than was the subsequent Milano Verde (Alfa 75) 3.0 liter V-6 are you not? Don't know if it would make any difference about the intake manifold, but I think I'd find out before purchasing a manifold off that engine were I you. Just a thought...."
 
The original question had been about HEADS, not manifolds. And (at least in the USA) the best person to ask about the heads, manifolds, and carburettors of the 2.0 and 2.5 carburetted V6's of the Alfa Sei and of the South African 3.0 carburetted V6 is undoubtedly Hans Milo, who has parted out a few carburetted 2.5's, built a very nice carburetted 2.5 '73 GTV6 (not a misprint) and a nice injected 3.0 GTV 6, and would undoubtedly like to go carbs on the 3.0 and go 3.0 on the carbed '73. The crux of the problem is that the head/manifold interface is quite different on the carbed and injected engines, whether 2.0, 2.5 or 3.0.
 
It has been suggested that the Sei had six single carbs, two triple throats, three twins, and even five carbs, and that the 2.0 V6 could well have had a different combination than the 2.5. The best information I have says that both the 2.5 (tipo 119 A1) and the 2.0 (tipo 119 A3) use Dellorto FRPA 40 carbs. My copy of the shop manual, however, covers only the 2.5. (It also, like all Alfa references I have seen, calls them Dellorto, not Del'Orto.)
 
The question still remains, how many? 6, 5, 2 x 3, 3 x 2, or perhaps even just one?
 
The Alfa Sei shop manual #2586, published 11-1980, says (p.99) "The carburettor" (note, single) "is made up of six downdraft bodies" and, later, "The choke system is installed on the air filter, with a throttle valve and lean-out device." Elsewhere, however, it does sometimes refer to "The carburettors" (plural).
 
So, what constitutes a carburettor? The Alfa Sei has six separate downdraft venturi bodies (and jets, float chambers) mounted on two throttle body plates, all served by one strangler system (or "choke", in American English). Count them any way you wish. (Consider the normal Spica engine, with four injectors, two throttle bodies, and one injection pump: is it a Spica injection, singular, or several Spica injections, plural? We usually consider it a single system.)
 
No Alfa content, but there is a parallel in pre-mobile engines. During the first century of engine building an "engine" was normally a building with walls, a roof, massive foundations, a cylinder, and sometimes a crankshaft. (Many were linear, not rotative.) When a second cylinder was added within the same walls you had a pair of engines in an engine-house. Twentieth century descriptions call the centerpiece of the Hall of Machines at the Centennial Exposition "the Corliss engine"; contemporary descriptions had usually called it "a pair of Corliss engines"; it had two cylinders, one crankshaft, one flywheel and one governor. The group of several engines didn't become a single engine with several cylinders, it seems, until they became mobile with the development of locomotives.
 
John H.
Raleigh N.C.
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