Starting a 6.4 Hemi swap

[Flyin6]

I was thinking about the differences between a 5.7 and a 6.4 hemi swap.

I have heard it said that the 6.4 is just a larger 5.7, and the added cost of the 6.4 is not justified. Well, a lot of that is subjective, but based on the facts alone, there are some substantial differences.

Obviously, the 6.4 makes a bunch more power, 485 vs 425. The torque is obviously higher with the 6.4 at 470 vs 410 for the 5.7.

For the average person, 425 HP in a Gladiator is all one would ever need, so that's almost not important.

When I started digging for numbers and facts, a big difference started to take shape. The 6.4 is a much stronger engine all around than the 5.7 Hemi. It is also better built, utilizing higher-quality components.

Starting with the exhaust manifold and hardware. The 6.4 gets better manifolds with upgraded aircraft-grade hardware. The crankshaft in the 6.4 is forged; the 5.7 gets a cast unit.

The 6.4 engine has oil jets in the block that spray cooling oil onto the underside of the pistons. The 5.7, not so much.

The 6.4 has a liquid-to-liquid oil cooler; the 5.7 does not. I believe the 6.4 has sodium-filled exhaust valves, and again, not so for the smaller cousin. The 6.4 has a thicker nickel/iron block than the 5.7. The 6.4 heads are basically a 6.4 version of the 6.2 Hellcat castings, which were built for boost and abuse. The connecting rods on the 6.4 are essentially Hellcat units, vs. iron on the 5.7.

You can even see the nod toward severe duty in the oil spec. 6.4s get 0W-40, where the 5.7 motors get lighter 5W-20. In every crucial area I examined, the engineers did a bunch more prep for severe duty in the 6.4.
Knowing this makes me feel much better about opting for the "truckier" SRT 6.4 engine over the milder 5.7 variety of this engine family.

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[shpion1]

hi, any info you can share on the cost? this is really close to me and a viable option depending on cost. cheers

 

[Flyin6]

hi, any info you can share on the cost? this is really close to me and a viable option depending on cost. cheers

I have not had the opportunity to talk to the owner about this subject, as I wanted to. My Jeep is their test mule, so I am seeing a substantial benefit.

I do remember, way back when, he was talking around $32,xxx + labor, but I believe the final numbers have not been settled.

This swap is not identical to the AMW with numerous different and costly parts, so there's that.

The concept of the operation is to install the system they have sorted out in my JT, then play with it to perfect it. I am local and willing to let them have my Jeep for extended periods of time to allow for some experimentation. Personally, I think their swap is really well thought out and will be nearly perfect with its first release.

 

[drewcnit]

Since you are waiting on your 6.4 swap, I thought I'd share my most recent drama with mine...
And no this is not because of the rain or a car wash...

There's a unique bend in the coolant hose, that apparently solved with a coupler right now and two hose clamps that apparently aren't going to work out....

Best picture I could get of where the leak is occurring. Had to get into an O'Reilly's and grab a gallon of coolant pre-mix to drop in her. Looks like one more thing to add to the punch list to get straightened out.

 

[shpion1]

I have not had the opportunity to talk to the owner about this subject, as I wanted to. My Jeep is their test mule, so I am seeing a substantial benefit.

I do remember, way back when, he was talking around $32,xxx + labor, but I believe the final numbers have not been settled.

This swap is not identical to the AMW with numerous different and costly parts, so there's that.

The concept of the operation is to install the system they have sorted out in my JT, then play with it to perfect it. I am local and willing to let them have my Jeep for extended periods of time to allow for some experimentation. Personally, I think their swap is really well thought out and will be nearly perfect with its first release.

Thanks much for background. Seems all $30k+

 

[Flyin6]

Thanks much for background. Seems all $30k+

For sure north of $30K
I explored Jeep Speed Shop, which has a sort of recipe of parts to get a Hemi in there, but I did not like it. The intake thing alone, then how and where to get all those parts, and...

 

[Flyin6]

Since you are waiting on your 6.4 swap, I thought I'd share my most recent drama with mine...
And no this is not because of the rain or a car wash...

There's a unique bend in the coolant hose, that apparently solved with a coupler right now and two hose clamps that apparently aren't going to work out....

Best picture I could get of where the leak is occurring. Had to get into an O'Reilly's and grab a gallon of coolant pre-mix to drop in her. Looks like one more thing to add to the punch list to get straightened out.

Oh man! That's no fun. Well, at least you get to burn your hands and skin a knuckle or two getting in there. You have that to look forward to! ;-)

 

[Flyin6]

I think I might start another 6.4 Hemi swap thread when we actually get going. This one is, what, 5 pages long with chit-chat and growing by the day. Chatting it up is good, but to better focus on the actual swap information, either I make a note of where the "good stuff" starts, or I start again when the time comes...

And

Happy Memorial day to everyone.
Slow hand salute to those who did not come home...Respect!

 

[RudeJeepin]

I think I might start another 6.4 Hemi swap thread when we actually get going. This one is, what, 5 pages long with chit-chat and growing by the day. Chatting it up is good, but to better focus on the actual swap information, either I make a note of where the "good stuff" starts, or I start again when the time comes...

And

Happy Memorial day to everyone.
Slow hand salute to those who did not come home...Respect!

A new thread sounds good. "The Actual 6.4 Hemi Swap" thread for the nitty gritty and this one can just continue for chit chat, pros and cons, questions, etc. Then the real swap thread maybe won't get clogged with nonsense.

 

[ltdodge]

You said 480 hp for the 6.4? My AMW swap has 505 hp. Why the difference in HP, didn't they use AMW engine?

 

[Flyin6]

A new thread sounds good. "The Actual 6.4 Hemi Swap" thread for the nitty gritty and this one can just continue for chit chat, pros and cons, questions, etc. Then the real swap thread maybe won't get clogged with nonsense.

I like it!

 

[Flyin6]

You said 480 hp for the 6.4? My AMW swap has 505 hp. Why the difference in HP, didn't they use AMW engine?

Same engine. AMW claims 505 HP, but SRT claims 485 HP. I'm going with the factory numbers.
Now, having said that, on a 93 octane or E85 tune, I'll bet most folks who tune could pull 505 out of that engine. In all likelihood, your engine is 485, but who really cares? What's 20 Horsepower when you've doubled the stock numbers?
Most folks in my research tune this SRT engine for 90-91 octane in this application. Out west, it is harder to find 92-93. Around the Midwest and the East, 93 is easily found. I plan to tune mine for 92. That should put it better than 485 and close to the 500 benchmark.

https://www.allmoparparts.com/sku/68303090aa.html

 

[ltdodge]

Same engine. AMW claims 505 HP, but SRT claims 485 HP. I'm going with the factory numbers.
Now, having said that, on a 93 octane or E85 tune, I'll bet most folks who tune could pull 505 out of that engine. In all likelihood, your engine is 485, but who really cares? What's 20 Horsepower when you've doubled the stock numbers?
Most folks in my research tune this SRT engine for 90-91 octane in this application. Out west, it is harder to find 92-93. Around the Midwest and the East, 93 is easily found. I plan to tune mine for 92. That should put it better than 485 and close to the 500 benchmark.

https://www.allmoparparts.com/sku/68303090aa.html

well, i the 392 wrangler comes with 470 hp and 470 tq, the crate engine comes with 485hp and with tuning 505 hp seems easily handled. but i can tell you the AMW pulls a bit more than then 392 wrangler, so i error on the side of closer to 505 with a 35 hp increase from the 392. could it be the gearing, tire size and 2wd vs 4wd?? all things are on the table

 

[Flyin6]

well, i the 392 wrangler comes with 470 hp and 470 tq, the crate engine comes with 485hp and with tuning 505 hp seems easily handled. but i can tell you the AMW pulls a bit more than then 392 wrangler, so i error on the side of closer to 505 with a 35 hp increase from the 392. could it be the gearing, tire size and 2wd vs 4wd?? all things are on the table

Concur-
It is very likely AMW could tune for more. Heck, I could have 550 HP, but with my rooftop tent configuration, your 505 HP would leave me in the dust. It's all relative, and no one ever could tell the difference of 25HP in a 2.5-ton vehicle.
Going from less than 300HP (212 at the wheel) to nearly 500 at the crank is something you notice. Beyond that, who really cares, certainly not me.
As you mention, the gearing and the size/weight of the tires have a much greater effect on performance. I'd bet if I kept my 5.13's (Which I am not doing) and kept my 37" tire, I would blow past your slightly more powerful Gladdy. But again, back in Pritchett Canyon, no one is ever going to notice.

 

[Flyin6]

I am relooking the gear ratio thing.

Look at the following numbers:

5.13 40.0" 70mph 2000rpm
5.13 39.5" 70mph 2050rpm

4.56 37.0" 70mph 1950rpm
4.56 36.5" 70mph 1970rpm

5.13 39.5" 75mph 2200rpm
4.56 36.5" 75mph 2100rpm

I have used the standard rounding error. 69.62mph = 70mph

Now look at the offset. A 40" tire, which is usually 39.5" in diameter, using my current 5.13 gears, is pretty close to the 4.56 with a 36.5" diameter tire! I mean, it is so darned close that if there were no other factors, it would suggest moving up to 40" tires and keeping the current gearsets.

I'll have over 350 ft lbs available at cruise RPM. Does the 3.6 even produce 100???

I really have to think this through. I know the 40" tire is going to weigh more, but how much more?? Will it make a significant enough difference to warrant other changes? Larger brakes come to mind, but I already have the best forged axles made, residing in the housings. I don't hammer on my Jeep, so in my view, the D44s would work just fine. And these late-model D44S are pretty close to the D60s of yesteryear...They're butt strong!

I know the Hemi in low range with my 4.1 Rubicon case will like to "push through" the brakes, but I have heard to place the transmission into manual and use 2nd gear instead of first. So that solves all of that.

I couldn't carry a 40" tire under the bed in the stock location, but moving it to the bed would yield more departure angle and ground clearance.
Losing the bed space is an issue with the rooftop tent, but I am looking at upgrading to a small camper to pull to a base camp, then dropping it and taking off in a lightweight, not-so-top-heavy JT.

This is classic foot bone is connected to the leg bone thinking, but I have to think about the JT as a system. So when I tickle the tire size, the thermostat reacts!

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