genealogy

[JHertzman@domain.elided]

In AD7-1199 Greg Stewart raises a question about engine genealogy: 
" Someone will surely correct me if I'm wrong, but I think the 1900cc 4 
cylinders were based on the same general architecture as the earlier 2.5 
litre 6 cylinder powerplants.

"Were the later 2.0 litre 4 cylinders and 2.6 litre 6 cylinders derivatives 
of the same family tree?"

It's a bit more complicated than that. The 6C 2500 of 1939-1951 was an 
enlargement (72 mm bore) of a Jano-designed 6C 2300 (70 mm x 100 mm) of 
1934-1939 which had been designed as a relatively economical replacement for 
the 
6C 1500/1750/1900 series which Jano had initially designed in 1924. In the 
late thirties Jano (who later designed the Lancia Aurelia and the successful 
Lancia-Ferrari GP cars) was dumped as a has-been by Alfa for his failure, 
underfunded and understaffed, to beat Mercedes and Auto-Union on the Grand 
Prix circuits. After Jano left, design work and some prototyping was done on 
several replacements for the 
6C 2300/2500; the S10, a 3.5 liter V12, and the S11, a 2300 cc V8, and, 
during the war, under Wifredo Ricart's administration, a new 6C 2000 car, the 
"Gazzella". All three shared much shorter strokes; 68 x 82 on the S10, 68 x 
78 on the S11, 72 x 80 on the Gazzella. After the war, when limited 
production resumed with the 2500, an ambitious replacement was projected, a 
6C 3000 with an 82.55 x 92 mm bore and stroke. It was this engine which was 
cut back to a four (82.55 x 88 mm) to make the 1900 and, with further 
development, the ironblock 2000. The 1900 in turn became the basis for the 6C 
3000 CM which, despite its "3000" designation, was a 3.5 liter car.

The 2.6 liter 6 cylinder engine shared the architecture and technology and 
parentage of the Giulietta, but has the distinction of being appreciably 
oversquare, at an 83 mm bore and 79.6 mm stroke. 

One can argue that the family tree and the most basic architecture goes back 
to Jano's 6C 1500, but the 6C 1500/1750-1900 was really one family, the 
8C 2300/2600/2900/3200/3800 a second family, the 6C 2300/2500 a third family, 
the 6C 3000/4C 1900/2000 a fourth family, and the alloy 4C 
1300/1600/1800/2000 and 6C 2600 a fifth family with a few distinguished V8 
members on the side, the 33 and the Montreal. Plus the boxers, the V6s, and a 
slew of competition projects. I'll leave out the Fiat-based engines, Perkins 
diesels, and prospective outsourced oriental replacements for the V6. The 
classic Alfa-Alfas are enough to get straight, more or less.

Enjoy them while you can-

John H. 
Raleigh, N.C.

------------------------------