[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.

[curtis73]

The amount of work it would take to bolt a TBI intake on a vortec head is so crazy that its never really done. Plus, the vortec ports are higher, so the TBI intake's ports won't match up very well. I suggest getting a 4-bbl vortec carb intake and make an adapter to put a TBI on it

[boatbob2]

Hi,if you make that conversion,your engine will run a lot cleaner (oil) BUT,have you priced propane lately???its over $4.00 a gallon here in north florida.

[oldbogie]

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.

Bogie

[Chevrolet4x4s]

About howmuch does the propane conversion cost?

Shane

[webcat]

You also will need to change your distributor gear to a Melonized distributor gear

Melonized distributor gear for when using roller cam with TBI distributor
19052845 - hardened Distributor Gear - .428" Shaft- (for use with small cap HEI Distributors with external coil)

http://www.rockauto.com/catalog/cata...LCO%2B19052845

[shane.,herold]

to run a tbi dist with a vortec block and cam requires this gear? what is the difference in the two?

[webcat]

i believe the steel is hardened
You need a melonized (hardened) distributor gear for use with roller cam
If you use the gear thats on the TBI distributor , it will eat it over time
around 40000 miles the gear will show quit a bit of wear