I see this question come up alot on this board and others, so I thought that my real world experiences would help out anyone considering swapping a NBS 4.3 to a NBS v8. I will update this again when the actual swap happens.
Truck:
2001 Silverado base model reg cab
Stock Engine/tranny:
2001 4.3 V6 / 4L60E
New Engine / tranny:
2001 LS1 5.7 V8 / 4L60E
I bought the LS1 minus a couple of key items: Wiring Harness, Alternator, A/C compressor, and Electric fans. Know from the start that all this info, unless otherwise noted, works for swaps from the 4.3 to 4.8/5.3/5.7.
Now some comments always seem to come up when people ask about doing this swap:
Question:
I'm swapping to a 4.8/5.3...Do I need a new wiring harness?
Answer:
Yes.
Question:
I'm swapping to a 5.7 LS1...Do I need a new wiring harness?
Answer:
Yes.
Question:
I'm swapping to a 4.8/5.3...Does the wiring harness have to be custom made?
Answer:
No. any stock wiring harness from a 4.8/5.3 will work fine and is fairly priced at about 400. the 5.7 wiring harness will not work, though. will not plug into the truck.
Question:
I'm swapping to a 5.7 LS1 and using LS1 accessories...Does the wiring harness have to be custom made?
Answer:
Yes. due to the location of the alt and the injector plug, a 4.8/5.3 wiring harness will have to be modified to fit. A custom made wiring harness would be easier to use here.
Question:
I'm swapping to a 5.7 LS1 and using 4.8/5.3 accessories...Does the wiring harness have to be custom made?
Answer:
No. any stock wiring harness from a 4.8/5.3 will work fine and is fairly priced at about 400. the 5.7 wiring harness will not work, though. will not plug into the truck.
Question:
Do I need to change out my radiator?
Answer:
No. the 4.3 has 28" radiator like the 5.3. but it's not a terrible idea to upgrade.
Question:
Do I need a new PCM?
Answer:
No, the 4.3 PCM can be reflashed. but if you search for it, you can find package deals of used PCMs and wiring harnesses for around 300.
Question:
I'm swapping to a 4.8/5.3...Do I need all new belt accessories?
Answer:
Only have a partial answer here...but NO, not all of them.
Question:
I'm swapping to a 5.7 LS1 and using 5.7 bracketry and intake...Do I need all new belt accessories?
Answer:
YES. you need all 5.7 accessories.
Question:
I'm swapping to a 5.7 LS1 and using 4.8/5.3 bracketry and intake...Do I need all new belt accessories?
Answer:
Only have a partial answer here...but NO, not all of them.
Question:
Do i need to replace the Fuel Pump?
Answer:
No. it is the same part. but new fuel lines may be needed.
Question:
Will the driveshaft have to be modified?
Answer:
No.
Question:
Will the stock intake system work?
Answer:
No. I'm having to buy an aftermarket intake system to get this done.
Question:
Will the stock tranny work?
Answer:
This is a big question. the stock tranny WILL work. :read: the bell housing is slightly different, but will mate up to the 5.7
Question:
Will the stock engine mounting locations work?
Answer:
no, you'll have to secure some 4.8/5.3L mounts and registers.
Question:
Will the stock exhaust system work?
Answer:
No. you'll either have to remake the entire system or get a 4.8/5.3/6.0 system.
so...if you are considering a swap to a V8, here's what you need:
swap to a 4.8/5.3:
complete engine
belt accessories brackets
4.8/5.3 engine mounts
4.8/5.3 wiring harness
new exhaust system
4.8/5.3 intake system
new PCM or reflash 4.3
swap to a 5.7 LS1 and keeping 5.7 intake and accessories:
complete engine
5.7 belt accessories and brackets
4.8/5.3 engine mounts
custom built wiring harness
new exhaust system
new PCM or reflash 4.3
new fuel lines
new a/c headers and lines
new evac lines
swap to a 5.7 LS1 and using 4.8/5.3 accessories:
complete engine
4.8/5.3 belt accessories brackets
4.8/5.3 engine mounts
4.8/5.3 wiring harness
new exhaust system
4.8/5.3 intake system
new PCM or reflash 4.3
So as you can see, the swap from a 4.3 to a 4.8/5.3/6.0 is not the nightmare everyone seems to make it out to be. with everything that swaps over...I see nothing wrong with dropping in a 4.8 or 5.3 even....you can get them cheap if you look. swapping to a 5.7 requires a bit more seeing that the belt accessories don't swap.
