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Have the 3.7 looking to swap to 4.7 or Hemi

33K views 24 replies 17 participants last post by  Paul Holmes 
#1 ·
:stickpoke: I dont know if it is possible to do this engine swap. But I know with a Jeep anything is possible. I want more power.
 
#2 ·
#6 ·
Look for a XK being sold with a salvage title or as a parts vehicle. You can pick one up for the cost of a crate motor and part out what you don't need. Other than trading in for a new commander that is the only thing I could say would be worth the time or money.
 
#4 ·
It is possible, but why not get a V8 to begin?
 
#23 ·
i agree 100%. engine swaps are usually not worth it unless you have a rare/classic vehicle (which are also cheaper and easier to work on anyhow). you're better off trading in the v6 for a v8, or get a v8 and keep both like many jeepers do :)
 
#9 ·
My suggestion for what it's worth...take out your 3.07 axle gear and put in the 3:73. That ought to give you the best bang for the buck. Replacing an engine is too freakin' expensive.
 
#12 ·
Well I watched this thread with some amusment back in 08.

Love the more power thing but on late model vehicles I can't suggest much more than jacking up the radiator cap and sliding a new vehicle under it.

Between getting a engine, trans, transfer case, both drive axles, ECM.....BCM,
all the necessary wiring......the list goes on.
Once done, you now have a freak that the EPA doesn't recognize as ever existing, a VIN that doesn't line up with the vehicle it is attached to, a vehicle that really can't be traded in and has zero trade value.

So, short of modifying the basic driveline, like supercharging, there really isn't anywhere to go.

Unless you have a really big checkbook and REALLY like that particular vehicle, and have a strong desire to make your life miserable that is.

Rob
 
#14 ·
Why not stroke out the 3.7? there would be nothing to change as far as powertrain and it would appear stock with matching vin #'s. Ive seen it done with jeep cherokee 4.0's stroked out to a 4.6 i think...but they claim it can produce close hp to a crate 350 but half the price. as seen on Trucks a tv show on SPIKE.
 
#15 ·
The 3.7 and 4.7 share the same bore size.....this, so the blocks can be machined on the same line.
However, had the stroke stayed the same, the 3.7 would only be a 3.5.
So, Chrysler beat you to the punch....they stroked it to get an additional 200cm and bring it up to a 3.7.

As I understand it, the crankcase area is rather tight so they likely took it as far as deemed commercially acceptable without weakening the block.

Rob
 
#16 · (Edited)
Well that def. answers that. hmm sounds like if u have a 3.7 and want a good bit more power the only logical thing to do is trade it in for a 4.7 or 5.7 but with the lesson learned from going too small with the 3.7 i believe u should always go biggest u can afford cause bolt on perfomance helps but that 3.7 just wont never be a V8
 
#17 ·
Unless you have a Junkyard Donor Car that you can pull all the odd and ends parts, I wouldn't even consider it. Its NOT that uncommon that there are parts that aren't even in the parts system to get and add to your vehicle for the engine swap.

Seen a lot of cars trying to do an automatic to manual trans swap, find out the clutch pedal is NOT in the part system at all, the junkyard was the only way to get it. There are bound to be lots of little brackets, pieces and connectors that are going to be hard to find, if NOT even available.

As well, tons of electronics boxes are going to be different, and try looking up the prices for each of those, even at adiscount, its stupifying.

You've got to find a junked V8 Commander, and even then, the same V8 as you plan to swap into your Commander, that you'll have almost exclusive access too to make this work and NOT be cost prohibative.
 
#18 ·
I forgot the place that I have posted previously that does 5.7 6.1 and 7.2 conversions. If you are going to go big, GO BIG!! II just rolled 91,000 and trying to rack up the miles so I can have my 7.2 soon. If we are all around in 3 years you guys should see the results.
 
#20 · (Edited)
I'm assuming the 7.2 Liter Conversion is with a Bored & Stroked 6.1L? I can't imagine trying to fit an old "RB" block into a Commander.

Something to keep in mind, the engine designers stick to certain rules to assure better wear and strength. People who bore & stroke a motor compromise those rules if NOT throw them out the window all together.

Seen more than one informed opinion that b&s a 6.1L out to 7.2L will make compromises that will end up the motor will need rebuilt in 50k miles, no matter how well you care for it.

Mopar Performance offers a 6.4L version of the 6.1L and parts for it, which leads me to believe that is as far as Chrysler is willing to b&s that motor and still put their name on it.

Not judging anyone, just letting people know what they are getting into, you get a motor b&s too far and its far more likely to break internally and wear out much sooner. Thats NOT to say there are NOT b&s motors and kits out there that are perfectly reasonable and are still reasonably reliable and long lasting, its just a matter of NOT taking it too far, and opinions will vary on how far is too far.
 
#19 ·
I'll be here in 3 years!
 
#21 ·
what about just getting new gear ratio to match the 4.7L? Thats what im planning on doing. it will be around 2000 if i have jeep dealer do it. i AM worried about power, but also im worried about take off. cause the 3.7L has a very bad take off with my super swampers on it. and my gas mileage shot down into the single digits. with the 4.7s gear ratio im sure it will bump my mpg back up some.
 
#22 ·
It sure will. That would be my recommedation to regear to 3.73's. If only someone could make some 4.10's or 4.56's we would all b e set!
 
#24 ·
if youre looking to swap for a 4.7 or a hemi you are looking at a price of 10 billion pesos.
but really...prob like 10 grand or so. i would say, if you really want more power that badly. get either a gear ratio upgrade to the 3.73 (4.7 gears) and it will help a lot. its about 2 grand for both axles. and will help in the end with your power. but for the 3.7L there is no programmer for it because the 3.7 is already maxed out in power by the dealership. the best you can do is intake and exhaust, which will only help at higher RPMs.
 
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