Hi, a practical question,
it will be easy for you or not (?) get longer conrods that can adapt to alfa 33 crankshaft?
Custom made conrods? AHM conrods? Or some from japan cars?
About travel vs bore,
I will be very interested in reading about you experimenting a super-square boxer,
this will remind me to history of Ing. Carlo Chiti in 1986-1990 working for Minardi and Subaru to design an engine with 12 "opposed cylinder" to be used in F1 ( "opposed cilinder" it is almost like a "boxer" engine but not exactly, a bit less balanced, infact I read it needed balancing countershafts resulting heavy and still not enough powerful for a winning F1 car of that period);
it was super-square configuration, 52,6 mm travel x 84mm bore, with heads with 5 valves ( 3 in + 2 out )
https://it.wikipedia.org/wiki/Subaru_1235
just, I have doubts that going very very far from a square engine, and despite the advantage of longer conrods,
engine could have an increase in total mechanical losses (thinking both about cylinder than about diameter of main bearings); any increase of RPM have a dramatic effect in mechanical losses; this will be not a problem if one is just searching for extreme power/result and not efficiency or durability, like F1 engines or motorbike engines, but using normal quality pieces, normal electronic, "normal" budget one can risk to get only the more mechanical losses and not the extremely high revving power?
Thinking on a limited budget, If I have to do a bet, I will imagine that your current configuration (already quite over-square engine) could be less difficult to pump-up than a more extreme one, but it is just a sensation, so think about what you will like to do, It will be brave and interesting if you try to realise it
About experimentation with different travel vs bore with Alfasud / Alfa 33 boxer engines,
if we consider also 8v boxers (not your situation, you want use the advantages of 16v heads )
I liked also:
>>> the history probably you already know of the Gordon Allen Alfasud in 1976 (1600cc but with 8v head), where you can read about different configurations travel vs bore he tried, this engine tuner pumped boxer engines (moderately, for street use, not to the level of a racing car) just a bit before alfa itself developed similar evolution (as it was already planned from start in the boxer project, but the tuner was able to anticipate commercial alfa plans in increasing only progressively alfasud engine power ):
https://www.motorsportmagazine.com/arch ... fasud-1600
>>> instead, talking of racing engines, I liked posts of this user (some more detailed posts about his engine are no more on-line. but below there is a link to a post there he put some infos and a couple of photos) that in the past (but I friend that contacted him says he is still actually doing similar development of alfa boxers) did a wonderfull work to improve 8v heads with brass sleves for tappets to get crazy revving and power for his race alfasud, also without the advantage of 16v heads ( 16v not only have an air section advantage, but also uses less heavy tappets and valves); he says he had to rebuild the gearbox after every single race, as from a 1600cc 8v alfa boxer he get 170-200 hp at 8500 rpm (and being able to go to 9000 rpm) with compression ratio 12,5:1 (custom pistons); he didn't need to go for a super-square configuration, he used the common over-square configuration 87mm pistons (as 1.7 boxer) and 1.5cc crankshaft;
https://www.alfabb.com/threads/alfa-sud ... pecs.6483/
>>> similar power figures (hp vs cc, with 1300, 1600 or 2000cc boxers) I have see where obtained from Autodelta in the past and also are currently obtained I have see in youtube videos from other people preparing for race Sprint or alfa 33 (not turbo);
but ok, 8v can be a different situation respect 16v, may be 16v (and a "small" 1400cc) could rev higher than this, super-square configuration will help keeping piston linear velocity within a target limit, but will not help limiting the speed for valve train and electronic, you will need quality pieces with design strong and light (and quality electronic and superior oil lubrification) that can afford 9000-9500 (?) rpm, if these rpm are eventually the ambitious target to get advantages from a super-square 16v configuration respect an over-square one, that maybe will have less demanding requirements and same power if you have to limit at a just a bit less rpm ?
It is just a doubt, I will like to read your ideas after you speak with some other people racing/tuning these engines