i am just womdering i am starting to make a intake manifold for my morris with a Datsun 1200 motor in it and i am wondering if there is any specific size the plemume and runners have to be to make it run properly or is it just make it a resonable size say 3 inch or 4 inch pipe into runners that have injectors on them

Any help is appriciated

if its a stock A12 then 3 inch runners is fine. I would use a camira ecu and throttle body and build the plenum around that. The camria ecu can also be remapped if need be. Use the camira injectors also...

It doesn't cover plenium volume, but there is some info on runner length here.

This website has a good article on working out plenum volumes and runner lengths etc, you want to read the article on induction systems
Click here

Just had a look at that link that you posted nick and that info is GOLD.... Thanks.

so for an A12 i would need a pleneum 50 percent of my Cylinder displacement which is what???? and what size would my runners have to be and how round? all this maths is just confusing me?

THanks

Just ran the maths quick and for a plenum 50% of the TOTAL cylinder displacement i.e 600cc you could make your plenum out of dia 63.5mm(OD) x 3mm x 225mm long extruded round tube, or dia 60mm(OD) x 2mm x 225 Long would work too. PM me if you need a hand with the maths, i couldn't be bothered writing out all the maths :)

that just seems a bit a bit small to me has any one here made a intake manifold and what are the deminsions that you used and how did it work?

any help on how long the intake runners should be for a stock a12 and what size???

easiest way i would do injection on an a12 would be to buy a single sidedraught weber manifold, an injection perfection throttle body, and choose a computer of your choice, fire it up and drive away. simple quick bolt on and a tune. fun to be had all round, if you don't get the concept of what these guys are saying bout plennum sizes and stuff, then y try yourself, sorry to b blunt but thats the game with modifieing cars