swapping from a NBS 4.3 to a V8

millerpro

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Apr 23, 2007
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Re: swapping from a NBS 4.3 to a V8

thanks for the info. also the guy helping me do the swap said i would need adapter motor mounts specificly for my truck. is that right? and my other question, will the bell housing mount up to the 5.3?
 

zebra86

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May 28, 2009
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Re: swapping from a NBS 4.3 to a V8

the bellhousing will bolt up fine, it'll just use one less bolt. as for the mounts, just get some OEM or equivalent V8 parts - engine and frame
 
Re: swapping from a NBS 4.3 to a V8

Just to reitterate, a 4.3 to a 5.3 swap would require the following:

Motor (of course)
Wire Harness
5.3 Mounts
Custom Exhaust
Intake
Reflashed ECM

The accessories (Alternator, Water Pump, AC Compressor, PS Pump) will switch over from the 4.3...right?
 
Aug 19, 2009
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Humble, Tx
Re: swapping from a NBS 4.3 to a V8

Bellhousing will work like stated above.......

You can go to a junkyard and get 99-07 Classic frame mounts and motor mounts..... Make sure its for a 2WD/Coilspring truck.

I wish i took more pics of the swap to show the difference between some of the V8 and V6 parts
...............................................................................................................................................................
As for the accessories: The alternator and PS pump will transfer over............. The water pump is different and Ac compressor mounts are in a different location

The stock exhaust will bolt up in same location as the V6(mine did, i dont see how anyone else should have a problem, yes it looks to restrict more but was just temporary)

The PS pump you will need to remove: the v8 and v6 have differents brackets that mount the ps pump to block so you will need to switch them.....
luckily i had a motor that came with everything except the pump was no good, so i just switched mine
 
Last edited:
Re: swapping from a NBS 4.3 to a V8

Bellhousing will work like stated above.......

You can go to a junkyard and get 99-07 Classic frame mounts and motor mounts..... Make sure its for a 2WD/Coilspring truck.

I wish i took more pics of the swap to show the difference between some of the V8 and V6 parts
...............................................................................................................................................................
As for the accessories: The alternator and PS pump will transfer over............. The water pump is different and Ac compressor mounts are in a different location

The stock exhaust will bolt up in same location as the V6(mine did, i dont see how anyone else should have a problem, yes it looks to restrict more but was just temporary)

The PS pump you will need to remove: the v8 and v6 have differents brackets that mount the ps pump to block so you will need to switch them.....
luckily i had a motor that came with everything except the pump was no good, so i just switched mine
Is there anything special with the AC compressor I'll need to worry about? Will I need new lines and such?
 
Feb 24, 2008
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Re: swapping from a NBS 4.3 to a V8

How does this compare to swapping in a 6.0L? I've decided to keep my truck mostly stock instead of lifting it up and all that fun stuff. Save my pennies for a Duramax and keep this on track duty.

Probably will still do a 5.3L since it's a lot easier to find one, but I might consider a 6.0L if it's not that much extra work and I can find a low mileage one.
 

zebra86

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May 28, 2009
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Re: swapping from a NBS 4.3 to a V8

Just to reitterate, a 4.3 to a 5.3 swap would require the following:

Motor (of course)
Wire Harness
5.3 Mounts
Custom Exhaust
Intake
Reflashed ECM

The accessories (Alternator, Water Pump, AC Compressor, PS Pump) will switch over from the 4.3...right?
the only difference in the exhaust is the manifolds. the 5.3 manifolds will bolt right to the 4.3 y-pipe - but i recommend going ahead & doing some LTs while you're in there. i sure wish i would've. the air box is the same, you just need a V8 intake tube to get to the throttle body (or make your own). if you have a 99 with the black PCM, you'll have to swap computers, but the 00+ 4.3 trucks use the same silver 0411 PCM as the V8s. the only accessories that swap over are the alternator & power steering.

Is there anything special with the AC compressor I'll need to worry about? Will I need new lines and such?
yep, you'll need new lines - the compressor's in a new location. there were a few different ones offered (based on cab config & air options). make sure you have the right compressor for your application & the different compressors use different lines, so double-check everything before you install. it took me a couple weeks to track down the right setup for mine.

ps - you'll be better off buying the lines new. you can reuse the condenser->accumulator line, but you need new lines that go off each direction from the compressor

How does this compare to swapping in a 6.0L? I've decided to keep my truck mostly stock instead of lifting it up and all that fun stuff. Save my pennies for a Duramax and keep this on track duty.

Probably will still do a 5.3L since it's a lot easier to find one, but I might consider a 6.0L if it's not that much extra work and I can find a low mileage one.
the only difference is the short block & tune.
 
Re: swapping from a NBS 4.3 to a V8

Another question: I found a good looking motor from an 09...the motor is supposed to work with the DoD system on the newer trucks; obviously that feature was never offered in 2003.

Can I still use this motor? or will the DoD system cause me problems?
 
Jan 26, 2007
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jc, tn
Re: swapping from a NBS 4.3 to a V8

questions?

What would be involved in swapping a 350vortec engine in an 06 with a 4.3 5sp
Also is there any other trannys besides the nv3500 that can be used.. needs to be street friendly and strong enough to tow up to 7-8k ..

thanks
 
Dec 19, 2010
26
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NJ
Re: swapping from a NBS 4.3 to a V8

Ive got a LS2 from a 05 GTO. Im guessing most of the stuff posted in here for the LS1 engines will apply to me? I haven't bought the truck yet, but it will most likely be a NBS 4.3 5spd or auto.
 

zebra86

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May 28, 2009
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Re: swapping from a NBS 4.3 to a V8

questions?

What would be involved in swapping a 350vortec engine in an 06 with a 4.3 5sp
Also is there any other trannys besides the nv3500 that can be used.. needs to be street friendly and strong enough to tow up to 7-8k ..

thanks
i looked into doing the SBC in a NBS when i did my swap but ended up going with an LS engine. i think you'd need new mounts, but you should be able to reuse the accessories/lines. why not go 6.0? as for a trans, i'd look at an NV4500 if you're gonna be towing that much on a regular basis. also ditch those crappy 3.23s & get some 3.73s with a TrueTrac. the trans has some way-low gearing in the first 3, so the 3.73s will be fine down low while helping you save a little on the highway.

Ive got a LS2 from a 05 GTO. Im guessing most of the stuff posted in here for the LS1 engines will apply to me? I haven't bought the truck yet, but it will most likely be a NBS 4.3 5spd or auto.
yeah, it's the same basic deal for all the LS engines. you'll have to work out whether or not you're gonna keep the cable throttle or switch to electric. it'll also be better in the low end to use a truck intake like from a TBSS or a GenIV if you switch the heads. check out LS1truck.com for a bunch of the specifics
 

zebra86

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May 28, 2009
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Re: swapping from a NBS 4.3 to a V8

questions?

What would be involved in swapping a 350vortec engine in an 06 with a 4.3 5sp
Also is there any other trannys besides the nv3500 that can be used.. needs to be street friendly and strong enough to tow up to 7-8k ..

thanks
ps - why wouldn't you get a 3/4 ton to tow that much all the time?
 
Dec 19, 2010
26
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0
NJ
Re: swapping from a NBS 4.3 to a V8

yeah, it's the same basic deal for all the LS engines. you'll have to work out whether or not you're gonna keep the cable throttle or switch to electric. it'll also be better in the low end to use a truck intake like from a TBSS or a GenIV if you switch the heads. check out LS1truck.com for a bunch of the specifics

Thanks. Also for the 5spd trans, do people get these 5spds built or are they swapping to t-56s? Im not planning on towing with this thing, just going to be a fun DD.
 

zebra86

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May 28, 2009
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Re: swapping from a NBS 4.3 to a V8

Thanks. Also for the 5spd trans, do people get these 5spds built or are they swapping to t-56s? Im not planning on towing with this thing, just going to be a fun DD.
no build kits for the NV3500 :(
it's fine, though. i talked to one of the engineers of the Joe Gibbs trucks & he said they had no problems with the stock trans behind their S/C applications making 425/390, so you'll be fine. i've also seen them abused behind built 6.0s, 454s & even an 8.1!

that said, yeah, people swap to a t56 all the time (so long as its 2WD). there's a huge write-up on performancetrucks.net that covers the swap, wiring, console mod, etc. just get some gear behind it & you're golden!
 

madwolf33

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Mar 27, 2011
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texas
Re: swapping from a NBS 4.3 to a V8

on my 89 c1500 i used every sencer and everything on the front of the engine alt p/s a/c w/p TBI the only thing i had to change was the prom the dis. and pull the temp sencer wire out of its harness to move it forward about 4 inchs and sence hooker headers ARE STUPID and put the 0-2 censer on top of the number 5 tube and i would have had to drill a hole in my floor board for it to work i just moved it to the end and the side so it would get readings from all 4 cyclenders but the wire was long enough to reach. and sence i kelp busting every trans i had went to a old turbo 400 witch now i cant seem to fine anything to make my speedometer work so haveing to use a GPS. on and i went from a 4.3 to a 383 stroker. the only thing it dont like is the cam so looking for a good cam that iwll go with my jet 6 pack chip
 

CookieSoup

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Dec 7, 2010
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Blacksburg
Re: swapping from a NBS 4.3 to a V8

sooo im new to the world of chevys... i did a motor swap in my subaru and its over 80 hours just to merge the wiring harness cause the ECU is intermingled with the dash harness... and to swap the motor you have to gut the interior of the car heater box vents and fans dash and seats to get the harness out to replace.

and your telling me all i have to do to put a 4.8 or 5.3 in my 06 NBS 4.3 is clip in the new wiring harness and plug in all the other lines and get an exhaust run?

if so holy butt nugget i might just swap the truck this summer for amusment sake. full motor and ecu and harness is about 800 bucks on ebay
 

joeAEKDB

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Mar 1, 2011
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Atlanta
Re: swapping from a NBS 4.3 to a V8

I am about to start this 4.3 to 5.3 swap in my 00 NBS, but I was wondering if the PCM would actually have to be flashed. I am asking this because I would be taking everything from the 5.3 truck (Only because I have the entire truck and won't be buying the parts and pieces separately). If this is the case it seems like I only need new upper and lower mounts?