1994 5.7 automatic swap into 1995 4.3 NV3500??

[aintnomoreusernames]

I spun a bearing on my 1995 4.3 with the 5-speed a while ago. So, to get by I went out and bought a 1994 5.7 with the auto trans as a donor. Due to my work schedule, I still haven't had time to tear them both down but pretty sure the auto trans is on its way out so the pressure is on to complete the swap.

I have read countless threads, everyday... for months and am still a bit confused on what parts I need to order so I can get the swap done in a 4 day window.

To clarify; I want to put the 1994's 5.7 TBI in place of the 1995 4.3 (vortec? the heads say vortec?) TBI with the 4.3's 5 speed (NV3500) behind.

DO I NEED FLYWHEEL / CLUTCH / THROWOUT? some threads say it will bolt right on, some say to trans swap from auto to manual I need a flywheel.

I know I will need to either swap or order:
5.7 Motor Mounts
5.7 Knock Sensor
5.7 ECU (or MEMCAL chip)
5.7 Wiring Harness
5.7 Fuel Pump????

I don't wanna take the running truck apart and be sitting around waiting on parts.

Can anyone help me with my parts list for this swap. Please?

 

[Schurkey]

"C" or "K" trucks?

The Chevy 90-degree V6 in trucks has been called "Vortec" since late 1984 (1985 model-year.) The "Vortec" name goes back much farther than most folks recognize.

That said, when folks talk about "Vortec", they almost always mean 1996 model-year and newer. Forget you ever saw the word "Vortec" on the valve covers. It's a TBI engine.

If both trucks are "C" or both are "K", just use the mounts from the donor vehicle. If you have one of each, I expect you'll be buying parts. Good luck if you're putting the engine into a "K" truck, decent mounts are not available as far as I know. Crappy weak, thin-steel aftermarket mounts are all I could find for mine. I re-used the original mounts.

I don't know if the V-6 flywheel has the same balance as the 5.7L flywheel. Look up flywheels for both engines, see if they're the same part number. Similarly, look up clutch disc, pressure plate, etc. Overall, it seems silly to me to re-use a clutch disc, pressure plate, and throwout bearing unless they've got unusually low wear. "I" would almost certainly buy new.

Don't forget to cram a pilot bearing/bushing into the 5.7L crankshaft.

Probably need to swap the radiator, rad hoses, perhaps the radiator mounts, fan shroud, and eliminate the external trans cooler that the 5.7L probably came with. Plug the holes for the in-tank trans cooler, or they'll drool. Might be a good idea to replace the hoses, and at least have the radiator cleaned-out if not replaced.

Verify the heater-hose quick-coupler on the two engines, use whichever one is in better condition--or get the Dorman replacement which is twice as good as the GM unit.

Pull the block drain plug and the knock sensor on the 5.7L, see how much sediment is in the water jacket. I replace block drain plugs with brass draincocks on my vehicles. The knock sensor will need thread sealer and a specific torque. Might make sense to pop out all the core plugs and put new ones in. If there's a lot of sediment, take the engine to a car-wash, or use a pressure-washer to blast through the core-plug holes while the core plugs are removed.

Good time to replace starter, alternator, water pump, O2 sensor, rear-main seal, damper/speedy-sleeve, front seal, and maybe timing chain, etc. while the thing is apart anyway.

If the A/C works good, don't open the system. If it doesn't work good, now is the time to get a fresh condenser 'n' receiver/dryer/accumulator, orifice tube, and all new O-rings after flushing the parts you're re-using (except the compressor, of course.)

I would connect a scan tool to the 5.7L truck BEFORE gutting the engine. Make sure all the sensors work, no codes, computer outputs seem reasonable. Then, if you have problems later, you know that the sensors and outputs WERE good. Similarly, I'd yank the spark plugs, verify the cranking compression pressure of all eight cylinders BEFORE taking the engine out, so you don't swap a wounded engine into the truck you're keeping.

Don't remove the exhaust manifolds from the engine unless you're prepared to replace them. Look 'em over for cracks, preferably before you pop the engine out of the donor truck.

 

[aintnomoreusernames]

"C" or "K" trucks?

The Chevy 90-degree V6 in trucks has been called "Vortec" since late 1984 (1985 model-year.) The "Vortec" name goes back much farther than most folks recognize.

That said, when folks talk about "Vortec", they almost always mean 1996 model-year and newer. Forget you ever saw the word "Vortec" on the valve covers. It's a TBI engine.

If both trucks are "C" or both are "K", just use the mounts from the donor vehicle. If you have one of each, I expect you'll be buying parts. Good luck if you're putting the engine into a "K" truck, decent mounts are not available as far as I know. Crappy weak, thin-steel aftermarket mounts are all I could find for mine. I re-used the original mounts.

I don't know if the V-6 flywheel has the same balance as the 5.7L flywheel. Look up flywheels for both engines, see if they're the same part number. Similarly, look up clutch disc, pressure plate, etc. Overall, it seems silly to me to re-use a clutch disc, pressure plate, and throwout bearing unless they've got unusually low wear. "I" would almost certainly buy new.

Don't forget to cram a pilot bearing/bushing into the 5.7L crankshaft.

Probably need to swap the radiator, rad hoses, perhaps the radiator mounts, fan shroud, and eliminate the external trans cooler that the 5.7L probably came with. Plug the holes for the in-tank trans cooler, or they'll drool. Might be a good idea to replace the hoses, and at least have the radiator cleaned-out if not replaced.

Verify the heater-hose quick-coupler on the two engines, use whichever one is in better condition--or get the Dorman replacement which is twice as good as the GM unit.

Pull the block drain plug and the knock sensor on the 5.7L, see how much sediment is in the water jacket. I replace block drain plugs with brass draincocks on my vehicles. The knock sensor will need thread sealer and a specific torque. Might make sense to pop out all the core plugs and put new ones in. If there's a lot of sediment, take the engine to a car-wash, or use a pressure-washer to blast through the core-plug holes while the core plugs are removed.

Good time to replace starter, alternator, water pump, O2 sensor, rear-main seal, damper/speedy-sleeve, front seal, and maybe timing chain, etc. while the thing is apart anyway.

If the A/C works good, don't open the system. If it doesn't work good, now is the time to get a fresh condenser 'n' receiver/dryer/accumulator, orifice tube, and all new O-rings after flushing the parts you're re-using (except the compressor, of course.)

I would connect a scan tool to the 5.7L truck BEFORE gutting the engine. Make sure all the sensors work, no codes, computer outputs seem reasonable. Then, if you have problems later, you know that the sensors and outputs WERE good. Similarly, I'd yank the spark plugs, verify the cranking compression pressure of all eight cylinders BEFORE taking the engine out, so you don't swap a wounded engine into the truck you're keeping.

Don't remove the exhaust manifolds from the engine unless you're prepared to replace them. Look 'em over for cracks, preferably before you pop the engine out of the donor truck.

Wow, Thank you for your very in depth response! Heck yeah! That vortec written on the covers has really been throwing my google searches in the wrong direction!

Both are indeed 2wd C1500 trucks.

I didn't think about cross-referencing part numbers. That will build a lot of confidence that I have all the right parts before I start. Good idea!

The 5.7 does have a trans cooler. I was planning on swapping as much of the 5.7's cooling system in as I can. It currently has an oversized rad.

The 5.7 is a rebuilt that has around 45k on it. I was given the receipt when I bought the rig. Both trucks have 270k+ on them.

The A/C on the 5.7 short cycles. Clutch on, clutch off, clutch on, clutch off. I was just going to delete it. We have about 2 months of A/C need here. Heat however is very important lol.

On the exhaust. Both trucks are cat deleted. EGR deleted. Does the Y-Pipe from a v6 go right onto the v8 manifold (can probably check part numbers for this info too huh?)


My ultimate goal is to send the 4.3 to a machinist and build it back up for a turbo application, so its coming out soon regardless. I just don't wanna get stuck driving a car to the job site .

 

[Schurkey]

The 5.7 is a rebuilt that has around 45k on it. I was given the receipt when I bought the rig.

I'd still check cranking compression, and "codes" plus data-stream, just to be sure.

The A/C on the 5.7 short cycles. Clutch on, clutch off, clutch on, clutch off. I was just going to delete it. We have about 2 months of A/C need here.

What's important is the A/C on the receiving vehicle, not the donor vehicle.

Heat however is very important

One of the things I deleted from my previous post--when I figured-out you were in Arid-zona--is to pop a block heater into the appropriate core plug hole while the engine is out, and the hole is easily accessible.

On the exhaust. Both trucks are cat deleted. EGR deleted.

Deleting the EGR without taking it out of the computer tune leads to excessive detonation. Be REALLY sure that engine isn't wounded! Connect a scan tool, look at the knock counts when driving it, especially when accelerating or going uphill.

 

[aintnomoreusernames]

I'd still check cranking compression, and "codes" plus data-stream, just to be sure.


What's important is the A/C on the receiving vehicle, not the donor vehicle.


One of the things I deleted from my previous post--when I figured-out you were in Arid-zona--is to pop a block heater into the appropriate core plug hole while the engine is out, and the hole is easily accessible.


Deleting the EGR without taking it out of the computer tune leads to excessive detonation. Be REALLY sure that engine isn't wounded! Connect a scan tool, look at the knock counts when driving it, especially when accelerating or going uphill.

OK will do.

The receiving vehicle has not had a/c since I've owned it. never even tried to charge it. The system seems to be complete, just never cared to mess with it. Replaced heater core and blower motor and control board one winter I was feeding cows at 4am. Those were brutal mornings til I got her fixed.

I am in the mountains of Arizona so a block heater would be so nice! Thanks for the tip. I only see them on diesel really here but can't hurt.

Yep, detonation is probably what killed the V6. ALOT of mountain grades. The 5.7 however seems to be tuned for it because unlike the V6 it hasn't ever thrown a code. The v6 would throw an EGR code every day. Got about 30k out of it like that .

But like you said running a scan is easy and can't hurt.

Thanks again for your help.

I found that the clutch kit for the 4.3 and 5.7 are in fact different. I have never done much with transmissions other than replacing gaskets and 1 spedo on a th350 (leaky sobs). So, I am still confused what that means for my situation. if the clutch kit is different for the engines, does that mean either one will work on the trans?
4.3 Clutch Kit
5.7 Clutch Kit

The flywheels are identical in teeth and size but appear to be balanced differently.
4.3 Flywheel
5.7 Flywheel

Cheap enough to just buy a new clutch kit and flywheel but still unsure what this means for installation on an NV3500. I assume a 350 woulda come with a 4500 in most trucks but idk.

Thanks again for pointing me in the right direction. Its all starting to make morse sense now cross-referencing parts