[alfa] Re: Alfa 6 - carbs

[George Graves <gmgraves@xxxxxxxxxxx>]

Yes, I misunderstood Mr. Milo, because I couldn't imagine what would be 
different about the carburetted heads vs the EFI heads, so I "jumped to 
the conclusion" that the poster meant 'manifold' when he wrote 'head', 
as this part would, indeed be different from the EFI setup. Subsequent 
research shows that Alfa Romeo of South Africa imported the rough 
cylinder head casting, the crankshaft, and special pistons and sleeves 
from AutoDelta in Italy. The heads were fitted (by ARSA) with larger 
valves to improve breathing, so there WAS a difference. The decision 
was made, early on, to go for more low-range and medium-range torque 
for acceleration out of the corners, rather than for big-end power. The 
Dellortos used were the same as those used in the Alfa 6, but were 
re-jetted and re-choked to suit the larger capacity and bigger valves. 
The original 2.5 liter engine was 88 X 68.3 mm, and the SA 3.0 liter 
was 93 X 72mm for a total displacement of 2934cc. This differs from the 
subsequent production 3.0 liter as found in the Milano Verdi and later 
3.0 liter 164s, which was 93 X 72.6 (total displacement: 2959cc) making 
the pistons slightly different, but the bores are the same. What's 
somewhat puzzling to me is going by the South African "CAR Test" 
magazine review of April 1984, showed very little increase in either 
acceleration or top speed over the US EFI version.

The Alfa Sei most assuredly had 6 single-throat down-draft Dellorto 
carburettors when it was introduced in 1979. Over it's production run 
(production stopped in 1984), the car certainly might have used 
different aspiration schemes. In fact it might have used different 
carburettor set-ups in different markets, and I do know that at some 
point the car was changed to the same Bosch L-Jetronic as the GTV-6.

George Graves
'86 GTV-6 3.0 'S'


On Nov 13, 2004, at 5:27 PM, alfa-digest wrote:

> Date: Sat, 13 Nov 2004 16:30:24 -0500
> From: "John Hertzman" <johnhertzman@domain.elided>
> Subject: [alfa] Alfa 6 - carbs
>
> 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.
>
George Graves
'86 GTV-6 3.0 'S'
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