here's some info on NBS 4.3 to V8 swap

[DemoN]

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.

[LS1Nica]

It looks like you hit all the points, great post.

[formulaforspeed]

great info. I have been considering this exact conversion.. 4.3 w/ 4l60e to a 6.0 w/4L80e

I have the wiring harness, ecm, exhaust manifolds, motor and tranny.

I guess I need to get electric fans, new brackets, new intake pieces and new motor mounts, and exhaust components too

[jerry2500]

Good info. May come in handi soon i hope.

[DemoN]

new info:

When swapping to a 2001 LS1...the fuel system on the truck is different. we ran into a slight speed bump there and had to get a new fuel rail for the LS1. something about the truck being a return system and the engine being a dead-head?

[Luke2kz71]

this looks alot like the post demon made on fullsizechevy the same day, just like 10 hours earlier..

http://www.fullsizechevy.com/forums/...d.php?t=144116

dont post somthing and call it your own... at least give the guy his credit man

[2k5Squirrel]

Originally posted by Luke2kz71@Mar 31 2005, 01:42 PM
this looks alot like the post demon made on fullsizechevy the same day, just like 10 hours earlier..

http://www.fullsizechevy.com/forums/...d.php?t=144116

dont post somthing and call it your own... at least give the guy his credit man

Yeah, what he said


Onyx, just put that you found this on another site and let James take the credit for it.


LUKE, good catch for your first post.

[DemoN]

strange that it looks identical to the post on FSC, huh??

hey...doesn't DemoN drive a onyx silverado too?? wow! what are the chances??


you are both tards

[DemoN]

i just searched his name on FSC..he has the EXACT same truck as me!! holy crap!!

[2k5Squirrel]

i thought you were this guy
http://forum.ls1truck.com/index.php?showuser=287

they always say you have a twin somewhere...i din't know trucks counted too