I am first and foremost a biker, just pop in to this forum now and again for help with girlfriend's Fiesta.
As stated above, you must remember that carbs on sportsbikes point almost straight down into the engine. This is so that the space available on a bike is put to the best use, but I also think there are meant to be some performance gains to it. Here is a google image to show that:
However, not all bikes are set up that way. Lower performance bikes would look more like this:
ie, with the carbs at a flatter angle. I don't know if running "downdraft" carbs in a "sidedraft" configuartion gives any issues, but I would guess it'd be easier to start with sidedraft carbs, like eg. from that bike as shown, which is a comparitively low-tuned 1300cc 16v air/oil-cooled engine. It's an XJR1300, in case that helps!
Bike carbs, particularly sportsbike carbs, can be very fussy about having the right volume airbox and the right length velocity stacks. Later-model bikes (particularly Kawasaki) often used ram-air, and if the pressure on the carbs isn't right, your carburetion will be all to shyt, so avoid Kawasaki carbs. Carbs for muscle bikes are typically more happy to run with individual sock filters on.
One other thing to remember about bike carbs - they will need to be kept synchronised. On a bike it is a once every... err... every so often type of job, I don't know if it would be better or worse for intervals on a car. Some bikes are better and worse for it, but most benefit from a check and synchro every 15 or 20k miles.
Yes, I would use a bike fuel pump for the reasons above.
Worth noting bike carbs will typically use two throttle cables - one to push and one to pull. They are much thinner than car throttle cables, and possibly not durable enough? Sure that can be got around, but it's worth considering. They are usually joined as a bank on a long bracket, and for the skilled fabricator you could change the spacing, but generally it'd be a PITA. I have to guess the bank will be too narrow, maybe you can account for that by using bendy eg. silicon tube connectors between your manifold and the carbs.
The sound and performance gains from having individual carbs are real, otherwise sportsbikes wouldn't have bothered, as it obviously costs lots more to make 4 than 1 or 2 carbs. I reckon it'd be pretty cool to have that kind of induction roar from under a car bonnet too!
Meh, maybe there's something useful in there
