Howdy, in need of advice

[Axeman]

Howdy, new to the forum. I have a 1990 Gmc c1500 swb. It was my first ride and after sitting for five or six years I finally decided to start working on it again. Unfortunately squirrels managed to destroy most of the engine harness and clips. A few months back after searching every scrapyard I could think of I couldn't find a replacement.
Recently I found and 89 chevy for about a grand with the same setup as mine, 5.7 350 tbi, automatic transmission, etcetera. The owner just says it runs hot.
I also found out from a buddy of mine he knows someone with a 350 lt1 with the harness and computer selling it for the same price.
My question is which is the better option? Taking the harness and motor out of the chevy or buying the lt1? Will an lt1 mount to a 700r4 transmission? If I get the lt1 will I need to replace other things as well?
If I buy the chevy I figured I could use the truck for any parts I might need but I ain't sure.

I apologize if this is the wrong forum for this.

 

[slippy3002]

LT1 will bolt in, just need the ecu and wiring. Someone on here did this. This was also a common swap back in the day.

Tylerz28 might be able to help you out.

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[sewlow]

Welcome!
Yup! You've come to the right place!

 

[BOTTLEDZ28]

Like mentioned above, the LT1 will be a direct bolt in replacement in your truck. You will the have two options for a transmission. 1: get a 4L60E trans and run it with the ECM from the LT1. Some minor tweeking to the tune may be required. 2: run an older 700R4 that doesnt require any electronic commands from a computer. If your current 700R4 trans has a lot of miles on it then it it should be rebuilt before it goes back in the truck so you need to decide on putting money into a rebuild or spending money on a low mileage 4060E and just tossing it in the truck.

FWIW, your truck will be a whole new animal with an LT1 in it. It will be night and day difference in performance from the TBI engine.

 

[TylerZ281500]

lt1s in 93 had 700r4s or the 4l60 brotheren bolted to them in fbodys so youll be fine swap should be fairly straight forward either way you go. keep in mind lt1s are reverse cooled which isnt a hug deal but still, the neat thing is your starting with a tbi truck so all your sensors are not controlled via the computer so just plug em into the lt1 and go type deal. there are a few good threads on lt1 swap on fsc theres a guy named jayb1rd i loved his build dont know if itll help at all http://www.fullsizechevy.com/forum/...rds-mediocre-truck-thread-15.html#post5786463

as for a tbi swap, super simple pull the one harness and computer plug the other in, if you know the engine is good dont worry about gaskets and rings but if its tired now is time for a rebuild.

 

[Axeman]

Thanks all, I think I'll take the lt1. Now will I need to swap out the dash harness too or could I get by with the stock one?

 

[TylerZ281500]

dash harness should be seperate of the engine harness. all your sensors to get the guages to work are not controlled by the computer on a tbi truck which makes things easy because all you have to do is plug your sensor wires back into the lt1 and it should work

 

[polar]

Yea if it was a Vortec, everything is controlled by the computer. Ask me how I know this?


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[TylerZ281500]

Yea if it was a Vortec, everything is controlled by the computer. Ask me how I know this?


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how do you know this?

 

[polar]

From getting rid of the ECM in my 98 when I went to carb and installed the trans controller. Everything is controlled by the computer


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