3400 top on 2.8, is it possible with stock ecm?

[no_doz]

Hi, Im just tossing around ideas but Ive always wanted to build 2.8 with a 3400 top end, could this be accomplished while still using the stock ECM/most of the stock wiring? I realize a computer tune would be in order, but could it be done & what would be necessary (computer/wiring wise) in order to use the 3400 top end on an early 90's rwd 2.8 or a 89 fwd 2.8 with the stock ecm?

[Guest]

Define "Stock ECM".

the 2.8 came in so many variants, and so many vehicles that the "stock 2.8 ECM" could be about 2 dozen different ECMs.

Since you mentioned early '90's (RWD) 2.8, that would be an S-series truck, since they were the last vehicles to retain the 2.8 after 1989 and up to 1993. This would be a TBI ECM, and while it could be made to work, but would require a custom intake to mount the TBI to. Then you have to decide if you want swap to DIS, which requires changes to the bin (or "tune"), or make that custom intake clear the dizzy location to retain a dizzy, the latter is something only a few people have done successfully.

The '89 FWD 2.8 ECM would be easier to use and has been used without tuning when a gen3 top end has been swapped onto a 2.8. It's also been used in stock form when a complete gen3 has been swapped in place of the 2.8. This is because both engines use port injection and can easily be run on the same OBD1 ECM. IIRC there were a few different MPFI ECMs used on the late '80's 2.8, but they all pretty much amounted to the same thing. Once you actually connect to them with a laptop to tune them, that's when it matters what the actual numbers on and in the ECM are.

[no_doz]

Thank you very much, youve been extremely helpful!! My thinking is that a TBI could potentially be mounted to the 3400 intake, although it may be too difficult (I havent looked yet). It may sound ridiculous but ive always been a fan of a properly set up early 90's TBI rather than port injection (I realize this may agitate some, but i like the simplicity/having less injectors to mess with).

Also assuming we're dealing with a 2.8 s10, what would be needed to detect crank position if eliminating the dizzy & converting over to a coil pack setup like the fwds use, and is this even possible if using a TBI ecm?

[Guest]

The problem with using a 3400 intake and plopping a TBI throttle body on top is that the 3400 intake was designed as a dry flow intake and may not work well when fuel is needed to flow through the runners. Some similar set-ups done by people in the past with various engines where port intakes have been modified to have TBI throttle bodies and carbs mounted on them seems to be that some cylinders get over fueled while other get under fueled. Fuel even when atomized doesn't like to flow as well as air on it's own through enclosed paths. For best results you would need to start from scratch and build a complete intake that would work well as a wet flow intake.

Yes, it is possible to use a TBI ECM with DIS, however, the 2.8 TBI ECMs have not really been hacked all that well and the parameters that need adjustment may or may not be defined well enough with existing tools to make the necessary changes.

On the flip side it's possible for an MPFI ECM to run TBI, but again, you would need to adjust certain parameters to do so, and I'm not really sure anyone has tested that out, but the code seems to be there to do it.

In the end MPFI gives better fuel delivery across all cylinders, better throttle response and better potential for upgrades (more power), so I would seriously consider the switch.