I’ve done a fair bit of work with fuel injection on engines and sometimes with weird intake systems. Basically we (the company I work for) always uses throttle body injection if the runner length between the valve and common plenum won’t trap the fuel from back-feeding (a very short runner messes the distribution up), or if the cylinders have siamese intake ports like the Stovebolt. Neither one really is that easy with multi-point. Usually MPFI fuel injectors need between 300 and 500 crank degrees of rotation to deliver wide-open, full RPM fuel and you don’t have that time between intake closing of cylinder 2 and opening of cylinder 1.
If I was doing a GM TBI I’d probably pick a 4.3L ECM setup and dual 700 TBIs (the newer ones with the small injectors used on the Iron Duke) on an Offy intake. The same distribution improvement from the dual carb should apply with this TBI. The injector phasing shouldn’t matter much, each throttle body fires at 240 degree spacing, the two injectors are offset by 120 degrees. I’d also put in the knock sensor and let the ECM do the timing and idle speed, if I could pick the red/blue (94/95) ECM and not the 7747, I’d go that way as that software has better idle speed control.
Last edited by Dale Ulan; 12/03/2023 5:04 AM. Reason: Missed one word.
