5.3 LS vs 5.7 Hemi vs 5.9 Magnum vs SBC 350

[Dvaniwaarden11]

In the next year I’d like to swap my 4.0 it’s pretty dang new so I assume I can get some money from it. I’m keeping my AX-15.

I’m leaning 5.3 LS because of the vast array of parts.

For those of you with any of these motors, what do you like about them and what do you not?

I’m trying to decide what I’m going to go all in on.

I love the sound of the V8’s and I want more power to be completely fine pulling an offroad trailer. Also would like more torque off-roading and would love to have enough power on the freeway and driving up hill to be driving with the flow of traffic.

I’m geared at 4.88 and Dana 30 front Dana 44 rear with chromoly shafts. All on 35s.

 

[Dvaniwaarden11]

For reference I have a 97.

 

[GregBelleville]

I see you're a fellow Comifornian, curious what your plan is to get around smog?

 

[SkylinesSuck]

After you move to Ohio, I suggest a Magnum v8 because more than enough power and the wiring is much simpler.

 

[Wildman]

To remain "legal" per the EPA you have to use the same year or newer engine to swap into your vehicle, so I'm not sure when Chevy stopped making the SBC but if you're trying to stay legal that option is out.

1) LS 5.3 or 6.0 or? They all have a good aftermarket following so like with most SBC engines parts are less expensive. Now to do the swap I'd budget a minimum of $5K and that is cheap and assuming you're using used parts.

2) 5.7 Hemi They have come down in price but are still expensive IMO. Most I can find in my area are $2K or more and that is just the engine. The wiring harness from Hotwire is worth every penny but it still isn't cheap. They are around $2K for the harness & a programed PCM. You'll need to find a mid 90's Dodge Dakota V-6 bellhousing to keep your Ax15. You'll need a 2005 fuel tank & a 2001 or newer dash also. I'd budget a minimum of $7K for this swap.

3) 52/5.9 Magnum IMO the cheapest and easiest V-8 to swap into your TJ since it's older than a 2003. A lot of time you can find a running Dakota or Durangoe or Grand Cherokee with a bad transmission for cheap. And since you're keeping the AX15 it doesn't matter. Again you'll need a bellhousing from a Dakota.
The wiring can be done by you. There is around 19 wires that have to be blended between the TJ & Magnum harness. Depending on what you bought the donor rig for you could do this swap for under $2K

 

[GregBelleville]

To remain "legal" per the EPA you have to use the same year or newer engine to swap into your vehicle, so I'm not sure when Chevy stopped making the SBC but if you're trying to stay legal that option is out.

1) LS 5.3 or 6.0 or? They all have a good aftermarket following so like with most SBC engines parts are less expensive. Now to do the swap I'd budget a minimum of $5K and that is cheap and assuming you're using used parts.

2) 5.7 Hemi They have come down in price but are still expensive IMO. Most I can find in my area are $2K or more and that is just the engine. The wiring harness from Hotwire is worth every penny but it still isn't cheap. They are around $2K for the harness & a programed PCM. You'll need to find a mid 90's Dodge Dakota V-6 bellhousing to keep your Ax15. You'll need a 2005 fuel tank & a 2001 or newer dash also. I'd budget a minimum of $7K for this swap.

3) 52/5.9 Magnum IMO the cheapest and easiest V-8 to swap into your TJ since it's older than a 2003. A lot of time you can find a running Dakota or Durangoe or Grand Cherokee with a bad transmission for cheap. And since you're keeping the AX15 it doesn't matter. Again you'll need a bellhousing from a Dakota.
The wiring can be done by you. There is around 19 wires that have to be blended between the TJ & Magnum harness. Depending on what you bought the donor rig for you could do this swap for under $2K

I think our regulations in CA are more strict than federal standards making engine swaps more difficult, someone more knowledgeable will chime in I'm sure.

 

[Wildman]

I think our regulations in CA are more strict than federal standards making engine swaps more difficult, someone more knowledgeable will chime in I'm sure.

They are. I'm not from CA but I know a little bit about what is needed. You have to take your vehicle to a referee station where they check your swap and make sure it meets the CARB requirements. From the friends I know who have done one you should go and talk to the referee station first and discuss things with them. If you do a search there is information out there on it.

 

[XCRN]

Highway RPM is going to suck with 35s, 4.88 and the AX15. You will be revving 2500ish at 70mph which is excessive for a V8. Most of LS equipped trucks are closer to 1800rpm on the highway. Im 32s, 3.73 and AX15 with a 5.3 and I am closer to 2100rpm but its still not great. I saw no real difference between 3.08 and 3.73 with an LS other than it being louder and less fuel efficient.

 

[GregBelleville]

They are. I'm not from CA but I know a little bit about what is needed. You have to take your vehicle to a referee station where they check your swap and make sure it meets the CARB requirements. From the friends I know who have done one you should go and talk to the referee station first and discuss things with them. If you do a search there is information out there on it.

I found the engine swap guidelines last night. Skimming through them it basically looks like for OBD2 equipped cars like a TJ, the donor motor must be OBD2 as well and same model year or newer. All of the emissions equipment including the trans, EVAP exhaust and intake must come from donor vehicle. If so, the ax15 is going to have to go.

The donor engine must also be from the same class of vehicle based on gvwr, meaning a heavy duty truck motor can't go in a light duty truck. This is the guideline I'd be most worried about with a v8 swap, is whether the donor vehicle rating is same as a TJ rating.

The donor motor must also be a California emissions rated motor (not federal).

 

[BlueC]

I'm not sure when Chevy stopped making the SBC but if you're trying to stay legal that option is out.

I have an answer for that. The LS was new in '97 Corvette, so SBC were powering everything else. 2003 was the last year of factory SBC gen I engines, and SBC Gen II engines, the "LT", were an option in trucks and vans until sometime around '08. People just like to refer to these engines as "Vortech" and "LT#" instead of SBC.

 

[BlueC]

Highway RPM is going to suck with 35s, 4.88 and the AX15. You will be revving 2500ish at 70mph which is excessive for a V8

2500 might not be "necessary", but it's not bad and won't hurt anything. My factory-stock HEMI truck turns around 2300 at 70. Fuel mileage is load dependent, not RPM dependent.

 

[Wildman]

I have an answer for that. The LS was new in '97 Corvette, so SBC were powering everything else. 2003 was the last year of factory SBC gen I engines, and SBC Gen II engines, the "LT" were an option in trucks and vans until sometime around '08. People just like to refer to these engines as "Vortech" and "LT#" instead of SBC.

Thanks... I thought the Vortech stopped around 1997.

I found the engine swap guidelines last night. Skimming through them it basically looks like for OBD2 equipped cars like a TJ, the donor motor must be OBD2 as well and same model year or newer. All of the emissions equipment including the trans, EVAP exhaust and intake must come from donor vehicle. If so, the ax15 is going to have to go.

The donor engine must also be from the same class of vehicle based on gvwr, meaning a heavy duty truck motor can't go in a light duty truck. This is the guideline I'd be most worried about with a v8 swap, is whether the donor vehicle rating is same as a TJ rating.

The donor motor must also be a California emissions rated motor (not federal).

The whole vehicle class thing sucks. And I didn't know about the transmission part.

Edit: I wonder if you got a engine that came from a manual transmission rig if you could keep the AX15?
With the 5.2 Magnum you could find a Dakota or Ram with a NV3500 which is very close to the same gear ratio as the NV3550.

 

[XCRN]

2500 might not be "necessary", but it's not bad and won't hurt anything. My factory-stock HEMI truck turns around 2300 at 70. Fuel mileage is load dependent, not RPM dependent.

Very true its not bad for the engine, they can take way more RPM for longer, but switching gears from 3.08 to 3.73 it dropped highway fuel milage and made highway drive much louder so it wears on you for long road trips. You can only go so big on a muffler under a TJ. I have at most 36in to stuff a muffler and a catalytic converter between where the Y-pipe megers and the tail pipe. Im going to try a larger muffler and smaller cat one of these days to see what happens, but I am not stuck to emission regulations so I do not need a 50 state legal cat like the OP is.

 

[BlueC]

You can only go so big on a muffler under a TJ. I have at most 36in to stuff a muffler and a catalytic converter between where the Y-pipe megers and the tail pipe.

I had not considered room for a muffler, which is very important.

 

[Wildman]

My Ram 1500 runs around 2200 RPM's @ 70 MPH and feels like it falls on it's face at those RPM's. I'd rather it be @ 2500-2800 instead.
I can't say what a LS is like so can only comment on the Dodge.

 

[XCRN]

My Ram 1500 runs around 2200 RPM's @ 70 MPH and feels like it falls on it's face at those RPM's. I'd rather it be @ 2500-2800 instead.
I can't say what a LS is like so can only comment on the Dodge.

I have drive a few different Silverados/Sierras from 2000s to 2010s with 4.8s and 5.3s in various states of disrepair and they cruise along fine at highway speeds with RPMs around 1800. It can pass staying in top gear, but to move quickly it needs to go down one gear. I just know for my situation, I personally would benefit more for gearing towards highway travel vs crawling gears. But even with a stockish 5.3 and numerically lower gears it should handle an off road trailer fine and have plenty of torque to make up for the lower gears.

 

[lBasket]

My Ram 1500 runs around 2200 RPM's @ 70 MPH and feels like it falls on it's face at those RPM's. I'd rather it be @ 2500-2800 instead.
I can't say what a LS is like so can only comment on the Dodge.

The LS makes it's power at pretty high rpm, I think my lq4 6.0 makes peak power at like 3500 and can sit at that rpm pretty happily

 

[BlueC]

The LS makes it's power at pretty high rpm, I think my lq4 6.0 makes peak power at like 3500 and can sit at that rpm pretty happily

IDK what LS your working with, or out of what, but my 5.7 truck HEMI is rated hp peak at 5,400 and tq peak at 4,200. It's funny what one person finds to be high RPM vs another. I know it's just semantics, but I find it funny. I consider the stock HEMI to be a nice mid-range engine.

 

[lBasket]

IDK what LS your working with, or out of what, but my 5.7 truck HEMI is rated hp peak at 5,400 and tq peak at 4,200. It's funny what one person finds to be high RPM vs another. I know it's just semantics, but I find it funny. I consider the stock HEMI to be a nice mid-range engine.

I don't have any concrete references. Just what I was remembering from figuring out what RPMs were ok before Moab. Was reading mostly forums

 

[Wildman]

IDK what LS your working with, but my 5.7 truck HEMI is rated hp peak at 5,400 and tq peak at 4,200. It's funny what one person finds to be high RPM vs another. I know it's just semantics, but I find it funny. I consider the stock HEMI to be a nice mid-range engine.

This is something to consider when looking at engine choices. The Magnum V-8 engines make their peak HP and TQ at a lower RPM than either the Hemi or LS.

The other thing to look at is your transmission choices. The Hemi or LS can get transmissions that have more options than the Magnum. While the 4 speed automatic behind the Magnum is OK the transmissions behind the Hemi or LS are better.

The new 8 speed behind the Hemi is supposed to be excellent from what I've read. It's on my future mod list.