GM TBI to IH engines

["Doug Mitchell" <dougm@domain.elided>]

I know something about GM TBI systems since I have read up
to install a '94 TBI 350 in my Scout.  It would seem that
the injection could be adapted to the IH engine.  The
hardest part IMO would be the adapter to the IH manifold.

The GM system is an integrated system that uses a MAP sensor
and O2 sensor to adjust the mixture.  Other sensors are the
throttle position sensor, coolant temp sensor, anti-knock
sensor, and vehicle speed sensor.  The system controls the
timing curve as well as the fuel mixture.  You shouldn't
disable the vss sensor as it affects driveability, but you
can easily order an analog--to-digital converter to convert
the speed impulse from your IH speedometer cable to a
digital format the computer can understand.  Then you'd need
the VSS buffer, a device that corrects the impulses from the
VSS depending on gear ratio and tire size.  It's been awhile
since I've been reading up on the system, so I can't
remember exactly what the VSS controls.  ...but it's more
than just the torque converter lockup.

Your best bet would be to buy a complete truck with a 350 in
it, and a standard tranny (the standard tranny computer and
PROM might work for the Scout as is).  You'd need the
sensors, harness, and computer.  Then you need the GM
service manuals from Helm, and a book from JTR on performing
GM computerized engine swaps to older vehicles.  It would
also be really nice to adapt the new electronic distributor
to the IH shaft.  Then you'd get the complete system.
...would really be cool for the bumped compression of 392
engines with 345 heads.  I know the throttle body will flow
plenty for an IH 392 engine to about 4000 rpm or so.  The
computer has enough learning capability that it would
probably run the 392.  The 345, being the same displacement,
would be a snap.  There is a company in Arkansas that can
burn you a custom PROM chip too, based on your applications.
...It all sounds pretty expensive.

You also need to modify your fuel lines to add a return, and
the TBI system runs at 15 psi as opposed to the 5 psi of the
carb'd IH.  ...so you might need to upgrade the whole
system.  You also should have a fuel tank with a sump in it
so you don't starve the engine when the tank gets low and
you're bouncing around.  Remember, there's no float bowl to
store fuel, so the engine depends on a high flow of fuel
through the lines.  ...and you need an electric fuel pump
too.

It is definitely a doable thing if you have enough cash.
I'd say to plan on up to ~$1000 on top of whatever you pay
for the complete system from a wreck.  ...custom chip, new
VSS buffer, analog-to-digital VSS converter, maybe a new
computer...

...too bad some of the Scout places haven't seen fit to make
a kit.  ...probably too much involved in R&D to make it
worth their while.

Doug
'78 Scout
'78 Traveler