Vortec engine swap??

herc61 · May 22, 2006

New guy here looking for some information and expertise. My boss has a 91 Chevy 2wd 1500 truck with the TBI 350 and is getting a good deal on a complete(everything), running (68k miles) 96 5.3 vortec engine, wiring harness and computer. He actually has to buy him some headers for his new motor. I know it will bolt up to his 700r4 and I will need to make a bracket for the kickdown, a longer throttle cable, I am guessing new fuel line fittings to hook up fuel and the other misc. things. My biggest worry is going to be the wiring harness. What is going to need to be done to hook up the new wiring harness to the existing harness to make the current dash indications work and power the ecm? Any and all info wil be greatly appreciated. Thanks

asilverblazer · May 22, 2006

96 5.3L?

redvett · May 22, 2006

A 96 was 5.7 SPI and just about nothing from the 91 TBI will work including the wireing, fuel lines, fuelpump, ECM v/s PCM, transmission (electric), I/P wireing and cluster. He may be able to use the block without the heads and his TBI manifold and heads and make it work.

herc61 · May 22, 2006

Sorry about that, I meant 5.7 . I do not know why I was thinking 5.3. Anyway, let me clerify what we are wanting to do. We want to rip out the OLD 5.7, wiring computer, etc.. and replace it with the newer one with all of the electronics, fi, etc... I want to do it right the first time and am wondering what we else such as wiring up the new harness to the existing wiring in the truck, new fuel pump(if the current fuel pump cannot supply enough fuel/pressure).This is why I am asking because I don't know. I am very mechanically inclined but I don't know everything. Although sometimes I think I do. Thanks for the replies guys. Keep em coming

Rolandd · May 23, 2006

You will probably need to take the entire wiring harness from the donor vehicle and install everything having to do with the electrical system. The ECM will be looking for specific calibrations on all of the (thirteen?) sensors that it uses to control fuel delivery and spark timing. Unless the sensors are the same, at best you will be in limp home mode becasue the ECM will think that the other sensors have failed. I read a great book on Ford systems a while ago that detailed how these systems work and why the swap you are now doing is complex. The book also encoraged these types of swaps when a donor vehicle was availabe for the duration of the project. The newer systems take into acount such things as the brakes being applied, power steering load, a/c, electrical loads, etc. to keep the engine idle speed constant and to adjust fuel delivery and timing for these loads. Without these sensors, the computer will think errors are occuring.

You may want to look into modifying the engine mechanicals for the older system unless this truck is really something that you love. You will lean a lot in this process whether it ever runs or not. However, I might recommend a course in transcendental meditation or yoga to keep you from jumping off a cliff when the thing won't run right after 300 hours of work.

Best of luck to you. This is a project I might have attempted ten years ago, when I was single and childless and had time on my hands.

redvett · May 23, 2006

Along with a lot of time you will need a detailed wireing diagram for the 91 & 96 trucks so you can rewire the harness's. The 95 up has an entirely new IP and the wireing is different. The fuel pump on the TBI is good for about 15psi & the SPI is about 50 psi also you are going from OBD1 to OBD2 and for one you have to monitor the fuel tank vapors. Good luck.

ken1mod · May 23, 2006

Way too big a problem, Rebuild and upgrade the old engine and systems. These are not the good old days when you could swap out a 6.2 diesel with a 350 gas burner. Its just too complex these days.

Ken

OUMike · May 23, 2006

Way too big a problem, Rebuild and upgrade the old engine and systems. These are not the good old days when you could swap out a 6.2 diesel with a 350 gas burner. Its just too complex these days.

Ken

<{POST_SNAPBACK}>

Thats actually quite the misconception. I was chatting with a guy in my drive through teller at my credit union. He had a 93' Silverado RCSB with a 98' 5.7 from a wrecked truck that was owned by his brother. He clamis that he made the swap with engine and PCM only. He says it was an easy swap. My local Chevy dealer concurs with this. I've never done this myself so I'm not sure, but thats the expirence I have with it. I was looking to do something simlar with mine, except from my 4.3 V6.

sablowme · May 23, 2006

wow you got one hell of a mess, being im farley new with these fullsize motors and comming from the s10 world of 4.3's ...lol id say have you checked with Painless wiring, i know when i wanted to do a v8 swap on my 95 s10 rummor had it that as long as you used new body style with vortec motors, and yanked pcm and all the other junk that it needed it would be fine, so id say if your pulling all of this out of the other truck and everything is good in the new truck id say go with it. But i got to give it to you guys the rest of the guys here have a good argument going and know there stuff

redvett · May 23, 2006

Think about this. A TBI engine has 2 injectors and a SPI has 8 injectors along with changing from OBD1 to OBD2 being the latter is much faster and also is a PCM not and ECM its not a simple swap. Heck the ECM & PCM wont even plug into each others harness's let alone run.

Someone is FOS or just doesnt know the difference between them.

OUMike · May 24, 2006

Think about this. A TBI engine has 2 injectors and a SPI has 8 injectors along with changing from OBD1 to OBD2 being the latter is much faster and also is a PCM not and ECM its not a simple swap. Heck the ECM & PCM wont even plug into each others harness's let alone run.
Someone is FOS or just doesnt know the difference between them.

<{POST_SNAPBACK}>

again...

I didn't see the motor sitting in the bay, I only talked to the guy.