Originally Posted by oakman
Hi this is my first post on the forum. I'm thinking of taking the sequential fuel injection off a 97 5.7 vortec and putting on an intake with throttle body injection ; like the 95 TBI . I know this sounds backwards but if I do this I can install an impco dual fuel (propane/gas) conversion. This conversion would be the old Fumigation type propane system (cheap to convert). The vortec sequential injection will only allow and expensive propane injection system $5500. If I was to put a fumigation system on (old impco system) the 5.7 vortec intake holds too much propane vapor and tends to backfire damaging the top end and melting the plastic air intake,not good!. This intake swap would even be sweeter if a performance RV (torque) X intake for the TBI could be recommended.I think this may be able to be done. Would I just need a TBI and computer out of a 1995 with the aftermarket intake? I have heard the vortec heads don't bolt to a Stock TBI intake ; What aftermarket intake? What issues would arise with emissions and O2 sensors etc. Hopefully it wouldn't be too complicated.The last point is what cams were put in the 1996-99 vortec ? Where some roller cams and others hydraulic ?
Thanks ahead of time hope to get some hotrodden advice.
First you need to check the smog laws where you live. Canada is variable from incredibly stringent to almost none from place to place. The modification of a Vortec to TBI would be a back date which is illegal, the question is whether you live where you'll be caught at the next inspection or not.
From a doing stand point you can get there with GM parts but you have to go back to the 1995 model year or older but not much older as you'll need a computer compatible with the 4L60E type transmission not the older 4L60 or 700R4. It will require the TBI itself; an intake that converts Vortec heads at one end to TBI at the other, Edlebrock and GMPP make such a manifold. It will require the TBI computer and wire harnesses as these are a lot different from the Vortec, this is a change from OBD II back to OBD I. This will be incompatible with the anti-theft system which will require modification. The Vortec fuel pump will have to be replaced with the TBI pump or a suitable regulator will have to be found to get the Vortec fuel pressure down to something the TBI regulator can handle which is a lot lower pressure than CPEFI of the Vortec.