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Well, I have been lurking on this forum for a while now, but the 4.3 in my 94 Sonoma finnally died and I talked my pops into helping me swap in a V8 after christmas. I noticed that its seems like everyone on here has swaped in an LT1, but we figured a 96-2000 5.7L Vortec would be easier and cheaper. I have the JTR manual, but I have a couple questions for anyone out there who is more knowledgeable than I.

1. The JTR manual says to match the engine with the transmission, but i figure that the 4L60E is computer controlled so switching the computer from the 5.7 should change the shift points, et cetera. I just wanted to make sure (even though the sticky says to keep the tranny).

2. Has anyone tried keeping the stock manifolds on this swap? I am probabally going to buy a set of Sanderson headers rather than go the 305 TBI manifold route, but if stock manifolds will work, I will put off buying them untill this summer.

3. Finnally (I know this post is getting a little long), can you adapt the wiring harness from the 94 4.3? I know you can from the 96+, but wasn't sure about my year.

Thanks.
 

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yanbu,

The '96-'00 Vortec 5.7 V8 swap is WAY easier in an S10 than the LT1 V8 is. All of the stock Vortec accessories fit in the S10 chassis with NO modifications required, whereas the frame has to be notched to fit the AC comp on the LT1 conversion. Also, it is extremely tight to get any sort of custom inlet air ducting to fit on an LT1 conversion, but the stock '96 up 4.3 inlet ducting and airbox fits the Vortec 5.7 perfectly in the S10! The Vortec 5.7 heads actually use the same ports & valves that the LT1 head has, except they are iron rather than aluminum, and they are standard flow vs reverse flow heads like the LT1 has. What this all means is that if you replace the Vortec 5.7 cam with a LT1 cam (I would use the GM ZZ4 cam for slightly more power) and use LT1 exhaust manifolds, then it will make the same 285 hp that the LT1's make! (figure about 315 hp with the ZZ4 cam).

As for your questions, the following is the answers:

1) NO, you cannot use your stock '94 4L60E auto trans behind the Vortec 5.7 V8. The '94 4L60E is a non-pulse width modulated auto trans that has a 12 pin connector, whereas the '96 up versions are pulse width modulated types that have a 13 pin connector. The '96-'00 5.7 ECM's will not be able to operate a '93-'95 model 4L60E auto trans, you must get the '96 up version.
2) NO, the stock Vortec 5.7 exhaust manifolds will not fit in the S10 chassis. You will either have to use the 305 TBI low performance manifolds or headers. You can also use LT1 exhaust manifolds on it, but they are extremely tight in the S10 (clearance to the steering shaft is minimal, and the AC evaporator box requires notching to clear them), but they will just barely fit and are as good as any of the POS shorty headers for power + never leak and run cooler in the engine well.
3) NO, you cannot adapt the '94 engine harness for use on any of the Vortec 5.7 V8's because they use an entirely different type of ECU that is not compatible with the connectors. Your best bet is to adapt a '98 up 4.3 S10 engine harness with the 6 extra wires required added for the V8, and then change out the fuse box connector with the separate connectors that the '96-'97 S10's use (the pin terminals in the fuse box connector from the '98 up harness will fit directly into the '96-'97 connectors). Then you can simply make an adapter harness that goes between those individual connectors and the firewall connector that is used on your '94 model S10. It is really a very simple conversion to make!! You can also use a '96-'97 4.3 engine harness as well (with the 6 extra wires added for the V8 injectors & fourth O2 sensor that the V8 has), but that harness is a bit more complicated to use in the earlier '94 back S10's, and also requires that a '96-'97 Vortec V8 ECU be used (use a '98 up V8 ECU if a '98 up 4.3 harness is adapted for use in the S10). You will have to add a EVO/Passlock module from a fullsize truck if you do use a '98 up version in order to disable the passlock theft prevention system (you can actually make the theft prevention system function for you by locating a hidden switch somewhere in your S10 that flows current thru the proper value passlock resister when turned on, but will disable the vehicle from running when turned off...great setup for theft prevention that the '96-'97 versions don't have).

Hope this helps you out!
 
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