I would go with the 6.4 because I believe it is the only aluminum block out of all the Mopar V8’s. Saves you close to 100lbs over the front axel.

I’m also a HP person so I tend to not buy a GT Mustang when they offer a Shelby or pass on a Base Corvette when I could get a Z06.

 

If compare the dyno graphs of both motors, you can see the 6.4 offers 50-60lb for more torque under the curve and a solid 50hp above. The issues are this, the 6.4 is offered in 3 configurations: car (iron block - 470-485hp/485tq versions), truck (iron block 410-429hp/429tq) and the crate motor (aluminum block 525hp). The truck version is a low powered version designed for low octane, automatic tranny only and 100k reliability. The auto is higher powered and differs in many respects but can be thrown in front of a manual or auto. The crate motor is a whole different beast. I’ve had Chargers and Challengers with both the 5.7 and 6.4, the powered difference is huge on the street, the increase in torque under 4K makes the 6.4 the better motor in all respects. However, given what it costs and the actual powered offered, if it was me I’d go LS and have an aluminum motor which makes the same power and weighs hundreds less, all the while having a platform that the aftermarket has perfected. Good luck!!

 

Has the Jeep been regeared? If not, this would be the reason for it being a slug.

 

Pretty sure its running 4.10s (I turn around 2100 rpm at 70 mph). Thinking of going 4.88 ( I do a lot of highway driving). Perhaps I should see how that feels first.

 

I have ‘17 JK 5:38 and running 40” and it’s still slow as grandmas ride. ~2400 at 70mph

VS.

‘08 H3T Alpha 5.3 and 37s 5:38 gears
Turning ~2000 at 70

Alpha is much more responsive and quicker
Engine specs ~same 300bhp but 8vs6 always wins.

I Have a set of 38s laying around, I’ll try them on JK and see if there any difference.


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I have ‘17 JK 5:38 and running 40” and it’s still slow as grandmas ride. ~2400 at 70mph

VS.

‘08 H3T Alpha 5.3 and 37s 5:38 gears
Turning ~2000 at 70

Alpha is much more responsive and quicker
Engine specs ~same 300bhp but 8vs6 always wins.

I Have a set of 38s laying around, I’ll try them on JK and see if there any difference.


Sent from my iPhone using Tapatalk

A JK will always be a slug on 40s no matter what you gear. The system just doesn't seem to like them. I have had 40s and 38s on a few JKs. Runs normal with 38s, put 40s on and it just never seems right.

 

If it isn't a rubicon, or maybe even if it is, new axles(at least a front) will be in your future if you plan on running a v8. Just something to think about

We have a friend that runs an LS (it is about 750hp...lol) that tends to tear up axles and shafts...

 

Just wondering, what is the ball park $$ to get a used base LS in the jk, harness, labor, engine and everything?

 

IF someone said, "Hey. I can give you about an extra 100hp for $6,000" - Would you do it?

I would. In a heartbeat.

 

If I had the cash...lol.

but you are right, If I was doing a power adder, I'd go supercharger or turbo setup.

IDK on the LS engine swap. I would say 10 to 15 ballpark.

All that being said, I'd do gears first and see if that works, much cheaper alternative.