More power?

[Jackrabbit41]

Kinda on a rabbit hole but I’ve read through a lot of old forms on getting more power out of a renix. What all bolt on stuff can do that’s actually worth it? A lot of guys talked about the 60mm throttle body from strokedjeeps but when I go to his website looks like it’s down. Anyone out there sell these still? I’d like to wake this thing up a bit. I have 36 iroks and 4.10 gears which don’t help but I’d like 20-40 more horse if possible. Just a lot of the threads online are so old, the parts don’t exist on the linked websites. Thanks yall 

[derf]

Honestly, not much of the cheap bolt ons will give you what you are looking for.

 

If your engine is typical, it's likely in need of a rebuild.  A slightly upgraded camshaft may give you some more pep.  But as far as bolt ons, most really are snake oil.  Especially for a low revving, mild motor.

 

A good tuneup wouldn't be a bad idea.  Sometimes just fresh spark plugs can make a big difference.

 

Most effective upgrade you can do is to swap out axle gears.  Matching the axle ratio to the bigger tires will make a big difference.  Some 4.88s would be a good upgrade for 36" tires.

[Jeeper1093]

Agreed on the regear!

[ThatJeepGuy]

Agree on the regear. I had 36 iroks and 4.56 many moons ago as my DD and it was manageable but wanted the 4.88s.

[75sv1]

40 HP would be stroker territory.  20 HP, maybe. The Jeep 4.0L was done fairly good from the factory. Some will say 15-20 HP from the head. Hornbrod did get 12 HP at the rear wheel from a 99+ Intake. So, 16 HP at the Flywheel. His motor was a stroker though. On a stock motor you might see 5-8 HP.  That is a might. A bore TB did help with some drivability issues on my lifted '98 XJ. Mainly on incline grades in WV. Regearing to 4.10s with 31's help too. 

[Jackrabbit41]

Id like to try the intake and TB either way. Question about the TB though, where can you buy a bored one these days? 

[Gojira94]

https://strokedjeep.com/

 

[Eagle_SX4]

1 hour ago, Jackrabbit41 said:

Id like to try the intake and TB either way. Question about the TB though, where can you buy a bored one these days? 

The 91+ and 98+ intakes don't fit the Renix head very well. The intake ports got moved in 91 for the H.O. motors. If you are going to do a 98+ intake it would be worth swapping the head as well. A 7120 or 0630 casting head would be a good candidate. If you run the newer manifold you can straight bore a H.O. throttle body to 60mm very easily. The only issue is adapting the Renix TPS to the H.O. throttle body.

[89 MJ]

I've done a lot of the easier performance mods you can do to a Renix 4.0. I have 4.10 gears with 31" tires as well as a 4.0 and a 5 speed, which I think

HO header

HO head (actually a whole HO long block, but bottom end differences are negligible)

Bored throttle body

4 hole injectors

High altitude CPS

 

The big one I have not done is the horseshoe intake swap. 

 

Having spent hundreds trying to hop up the 4.0, I can confidently say that they did not add 20 hp to my truck. I would like to do the horseshoe intake at some point so that it will match the intake runners in the HO cylinder head better, but I highly doubt it will add a noticeable difference. If I could do it all again, rather than swap my truck's original rod-knocking Renix 4.0 for a good, low mileage HO 4.0, I should've swapped to an LS and had the power level I was happy with and (likely) better fuel economy.

 

[neohic]

1 hour ago, 89 MJ said:

… I should've swapped to an LS and had the power level I was happy with and (likely) better fuel economy.

^This. Even after building a mild stroker, I’d never do more than a quick rebuild on a 4.0 again. The power is nice, but after moving from MN to the higher altitude on CO it just feels more like a brand new 4.0. 

[derf]

I'm going to be giving a 4.6 stroker a try in my next project.  More power and torque without the headaches that come with swapping in a different type of engine.  All I have to do is pull one 4.0 block and bolt in a different one.

[ghetdjc320]

Well, I guess just to add to the conversation, after having built many a 4.0 and stroker variations thereof, an LS swap is my go to and I don’t look back. That being said, the best bang for buck was a stock 4.0 bored .060, with an edelbrock head, decked down for an .038 quench and about 10.75:1 compression ratio. That engine build was a few grand but less than my other strokers. With 4.56, my aw4 and 33’s, It performed admirably. But still no where close to a true LS swap. I’d like to try forced induction as well on a 4.0 as it would be a good candidate. But ultimately, it’s a tractor engine with a terribly outdated design. I don’t mean to disparage it to much but realistically, you don’t really notice an extra 40hp on a 4.0 given the power band. And you can sink a ton of money into them with very little to show for it. Even at 300hp, still feels like an anemic boat anchor. Forced induction, gears, or an engine swap would be my go to. And gears would by far be the most cost effective of the three. 
 

 

[Torq_Shep]

I struggle so much with this. My 4.7 stroker is a dog but it's tuning and exhaust I think. It's starting to make noises that I would hope are top end but I am nearly certain are bottom end. 

 

The unbeatable low end torque of the 4.7 is awesome. It's so good. But it's not a revver. Basically useless after 3.5-4k. An LS would be great but I worry that it would ruin the nostalgia of driving the i6. 

 

 

[neohic]

8 hours ago, Torq_Shep said:

… An LS would be great but I worry that it would ruin the nostalgia of driving the i6. 

 

 

^This also. I love my stroker as a 6 cylinder. I’d never build one ever again though. 

[ghetdjc320]

Once you go LS, you won’t go back 

[Porquer]

My advice is to drive a 2.5. Then your 4.0 will feel great!

[neohic]

22 minutes ago, Porquer said:

My advice is to drive a 2.5. Then your 4.0 will feel great!