4.3 to 5.3 details

I saw this post by 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." END QUOTE

I have a 94 4.3 2wd 1500 that I would like to put a V8 into. Going to a 5.3 seems like a good enough power increase to justify the work, but also keeps the cost affordable to me when compared to the LS1 conversion. I have been pricing motors from salvage yards and most of the guys I talk to want to to swear to me that the stock 4.8 and 5.3 harness's won't plug straight into the 4.3. Has any one here done the 4.3 to 5.3 first hand?

This site http://www.hotrodlane.cc/ shows some pretty good info on LS1 conversions(but no 5.3). I was wondering if anyone has any leads for specifics on the 4.3 to 5.3 swap. Most guys going to V8s probably don't bother with 5.3s, but a write up would be pretty nice to study.