onyxsilverado

i can't remember if i ever posted this here...but seeing that i've seen the question come up a few times...i thought i'd post my expereince on the subject.

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.

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. 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 acessories:
complete engine
belt accessories and brackets
4.8/5.3 engine mounts
custom built wiring harness
new exhaust system
new PCM or reflash 4.3

swap to a 5.7 LS1 and using 4.8/5.3 accessories:
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

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.

RedChevy4x4

iTrader: (5)

Good info.

ap2002

iTrader: (8)

Nice write-up...

bluecajun5.3

iTrader: (31)

good job man. keep it up!

2toneblown

iTrader: (5)

good information man. As many threads that i see about this i would say make it a sticky