hi starting a tbi conversion on 78 vette

[cobrareg]

just starting to piece together the harness and parts to start the conversion. please give me any advice you may have for this process.
thanks
reg

[dave w]

I think having a good wiring diagram is essential! I think either a Camaro or Caprice TBI systems from the early 90's are good systems to adapt for a Corvette. I like the fact that the Camaro and Caprice TBI system use a Manifold Air Temperature sensor.

dave w

[RobertISaar]

depending on what transmission is being run is what i would base my recommendation off of.

[cobrareg]

The current engine is the stock 350, 4 bbl. It is a 4 speed transmission. I added vortec heads to it a few years ago. I found a 89 truck tbi setup, minus the ecm and vss locally for $100 that I am thinking about picking up. It is supposed to have all the the sensors, wiring harness, tbi and distributor. Does that sound like a good start?

[EagleMark]

Yup, that will work for ya! ECM is about another $40. aftermarket VSS about $100. Lots of time and some tuning and you'll be stylin! :thumbsup:

EDIT: It's off a 5.7L engine right? You need the 5.7L TBI.

[cobrareg]

With a manual trans, do I need to hook up the vss ? Some posts say I do and some say I don't. I was thinking about the in tank fuel pump. I've read that I can use the in tank fuel pump and sending unit from an 82 vette and it will work. Looks like the whole thing is about $170. Is this early wiring harness pretty easy to sort out, or will I need to buy one already tailored for the conversion? I can at least use a volt meter and trace wires.

[EagleMark]

EFI Conversions are always better with VSS, that said you can go without on this ECM. That harness will be fine to rework. Nice deal you have an in tank drop in replacment, will need high pressure line from it to TBI then low pressure retrun line back to tank.

[gregs78cam]

If you haven't bought the harness yet, see if you can find one from a '94-'95 with PCM, there are many advantages to using the later PCMs. Or you can re-pin the early harness to work with the later PCM, either way it's not too hard.

[cobrareg]

Most of what I have read says to use the early tbi ECM and wiring. What would be the benefit of using a later ECM and wiring harness?

[JeepsAndGuns]

The only downside to the later tbi pcm's is a slightly steeper learing curve. While everything else is better.

[gregs78cam]

Most of what I have read says to use the early tbi ECM and wiring. What would be the benefit of using a later ECM and wiring harness? '7427 was basically the final OBD1 TBI PCM put out mostly in trucks/vans to cover most any engine/trans combination. Way more tables and constants to change, faster ALDL stream (~6 samples per second vs. 1 sample per 1.2 seconds) with much more to see, and a few extra things that users have figured out how to add for functionality(WBO2, E-Fan, MPFI).