Interesting debate on who made the first series of Tipo 33 engine and its up to history researchers to find out for sure. Books some times tell diffent stories. In the Carlo Chiti Grand Prix book its only mentioned that he constructed a new car and V8 engine. So what he took with him of ideas for the new V8 engine maybe was only in his mind. Also its mentioned elswhere that the ATS V8 engine was a copy of the Ferrari V6 F1 engine, with regards of technical details. So copying over several generations of engines?
ATS being a very obscure brand from Italy in the sixties, and this site being an Alfa site, therefore knowledge of ATS here probably is close to zero. In the Chiti Grand Prix book there is only photo of the road 2,5L engine which is a single cam V8. So getting anything on the F1 1,5L twin cam V8 was not quite easy. However there is some material on this engine in a book. Just to get an idea to the discussion here and even get a photo of it. On the retrieved photos it can be seen that the 1963 version was quite different from the Tipo33 engine, however the 1964 ATS engine looks more like the Alfa. This actually means nothing with regards of the Alfa ancestry, but maybe there is a chance? How close are these constructions?
The retrieved texts and photos from 1,5L F1 engines of the sixties: p. 288-289
If you are interested in ATS, than Michael John Lazzari book, “ATS. La scuderia bolognese che sfidò Ferrari”, (Maglio Editore, 2012) is good starting point (I do not know if there is English edition too). ATS 2,5 liter engine has nothing to do with 33 project and it was not Formula 1 engine. It was produced for ATS GT 2,5 and it is another story, not for this forum. Ferrari V6 engine used in F1 was 120° and different architecture, and so, obviously not the inspiration for 90° V8. Chiti at Ferrari has worked on 158 F1 engine project in 1960 (later developed by Forghieri) used in 1964 F1 season. It was 1500 cc,V8, 90°, 2 OHC two valves for bank, 5 bearings, dry sump, ecc, very similar to his 1500 cc,T100 ATS F1 engine built in 1962, and both those motors are close relatives to 33 engine. I do not understand continuous claiming of Giuseppe Busso’s authorship of 33 motor (chassis and the majority of general solutions were his work) as Busso himself has never mentioned (not even in autobiography) V8 for 33 as his project. Maurizio Tabucchi author of important books about Alfa Romeo (close friend of Chiti) is explicit about that: “…Luraghi’s decision was immediate; Chiti would complete 33 project, and Chiti would conceive the new engine for it, an 2 liter V8 unit…”
“…La decisione di Luraghi fu immediata: la 33 l'avrebbe terminata Chiti e avrebbe progettato anche il motore, un 8 cilindri da due litri…“ (Maurizio Tabucchi, “AUTODELTA”,1967, GLI ESORDI DELLA 33, page 80) Another controversy is about produced Stradale cars.
Here are numbers:
750.33.01 (four lights, prototypo, body probably in aluminum) Autodelta factory
750.33.101 (two lights, first production car, body in Peraluman H33) Carrozzeria Marazzi
750.33.102 same as above
750.33.103 same as above
750.33.104 same as above
750.33.105 same as above
750.33.106 same as above
750.33.107 magnesium chassis, fiberglass body, 270 bhp engine, used for racing
750.33.108 Concept car (Pininfarina Roadster, rebodied in Cuneo)
750.33.109 Concept car (Bertone Carabo)
750.33.111 same as first production car
750.33.112 same as above
750.33.113 same as above, renumbered in 750.33.133
750.33.114 2,5 liter engine, racing trim (Giro d’Italia)
750.33.115 Concept car (Pininfarina 33/2 SC)
750.33.116 Concept car (Giugiaro Iguana)
750.33.117 Concept car (Bertone Navajo)
To replace sold prototype (750.33.01) sold in Japan, Autodelta build on magnesium chassis from dismantled racing car (number 750.33.012) four light version renumbered in 105.33.12
Though I did accurate inquiry (as possible), I cannot guarantee absolute correctness of chassis number data.