Rebuild Options For 50-75 More Horsepower?

[Buck Steele]

I need more power! 3.7L with 210K miles, but we live and drive at high altitude. Pulling my little boat over the Utah mountains isn't working. How can I get another 50 or 75 ponies?

If this were a V-8 I'd rebuild it and get some better heads, a little bit of cam and make it flow. But, who makes a better set of heads and cams for the Jeep 3.7?

Is there another way to get some power - short of buying another vehicle?

 

[lfhoward]

Regear your differentials to a lower gear ratio like 4.10. (It’s 3.73 stock if you have the automatic ******). Then you can do burnouts and have more grunt for towing, without changing the engine. There’s not much available power in the 3.7L V6 unfortunately.

 

[LibertyTC]

What length & what is the weight of your little boat loaded ? I was shocked when I put mine across the scale at 3700lbs.
The KJ is only 210 HP & mountain pulling leaves you wanting a Grand Cherokee V8 real quick.

 

[Buck Steele]

What length & what is the weight of your little boat loaded ? I was shocked when I put mine across the scale at 3700lbs.
The KJ is only 210 HP & mountain pulling leaves you wanting a Grand Cherokee V8 real quick.

My 16.5' 40 HP boat weights 1,640 lb total on the trailer. (Yes, I weighed it)

I depart Cedar City, Utah at 5,500' altitude, drive over a summit at 10,600' and down to the lake at 8,300'. That's 7,400' vertical feet of climbing for each round trip, winding up and down canyon roads.

The 210 HP engine probably makes 180 at sea level now that it has 210K miles, but maybe 130 or 140 HP at 10,000' altitude. See the problem? Weak engine + wear + altitude.

I need more like 280 HP at sea level to get 210 at these altitudes. (Yes, pilot and airplane owner. 180 HP Lycoming O-360 in a Vans RV-4).

Gearing is not the problem. But, If I could command the trans to stay in a higher gear at full throttle that would help a little. Screaming around at 5,000 RPM just to make some power is not a good solution. I need to do 40 to 60+ MPH going up long, steep canyons, not pull up one little hill at 20 MPH.

So, is there a replacement engine or rebuild ( or other option???) that will make 270-300HP, and still have a nice reliable Liberty?

 

[LibertyTC]

The simple answer is no, don't bother.
We have had V-8 discussions, and it would be easier to purchase a more powerful rig with more gears, for your application.
https://www.jeepkj.com/threads/ok-so-lets-be-serious-4-7l-swap.53310/

 

[tommudd]

To be quite honest, if you want that much HP, trade it off to someone who enjoys owning a KJ
or dig very deep in your pockets and install a V8, different transmission, different transfer case , rear diff may handle it but front won't if you hammer on it at all, so new front diff which would require doing a SFA
PLUS regearing will help you now even though you don't think it will, but it does

 

[Buck Steele]

Thanks guys. Sounds like good advice from each of you.

 

[Robochop]

I need more power! 3.7L with 210K miles, but we live and drive at high altitude. Pulling my little boat over the Utah mountains isn't working. How can I get another 50 or 75 ponies?

If this were a V-8 I'd rebuild it and get some better heads, a little bit of cam and make it flow. But, who makes a better set of heads and cams for the Jeep 3.7?

Is there another way to get some power - short of buying another vehicle?

I have done several 3.7 valve/head jobs here in Virginia. My machine shop guy told me that he could increase the size of the head intake ports so you can get a little more power. I haven't tried this but I'm sure this won't help your fuel consumption tho! The aluminum heads have enuf heat issues as it is with dropping valve seats when it overheats. Just my opinion...Good luck!

 

[Buck Steele]

Thanks. I see an consensus emerging. I appreciate your collective expertise.

 

[profdlp]

Everyone I know who did the re-gear was glad they did. I'd like to get my own done.

 

[Buck Steele]

When I'm crawling around the rough country those gears would be excellent! Low range is nice, but on many of these rocky trails more would be better.

Prof, are you a University Professor by any chance? I volunteer to Co-Teach an Engineering class here at Southern Utah U (ENGR3030 Project Management), and advise Senior Engineering Projects. It would be super-cool to do it full-time! Maybe in the next lifetime.

 

[profdlp]

My username goes back almost 25 years and is a reference to a literary character. (Bonus points if you can guess where profdlp came from. Hint: A sci-fi book which won a Hugo back when that meant something.) The closest I come to being a real prof is my tendency to be didactic. ;-)

 

[tommudd]

When I'm crawling around the rough country those gears would be excellent! Low range is nice, but on many of these rocky trails more would be better.

Prof, are you a University Professor by any chance? I volunteer to Co-Teach an Engineering class here at Southern Utah U (ENGR3030 Project Management), and advise Senior Engineering Projects. It would be super-cool to do it full-time! Maybe in the next lifetime.

No matter in town on a rocky course 4.10s do way better
I have them in two of my KJs and made a world of difference in both
Pulling hills , towing trailers, or just cruising , way better

 

[tommudd]

When I'm crawling around the rough country those gears would be excellent! Low range is nice, but on many of these rocky trails more would be better.

Prof, are you a University Professor by any chance? I volunteer to Co-Teach an Engineering class here at Southern Utah U (ENGR3030 Project Management), and advise Senior Engineering Projects. It would be super-cool to do it full-time! Maybe in the next lifetime.

Go for it, become a Professor , my wife is a Professor at a University in North Carolina
she started teaching, helping other Professors , doing the grunt work as she calls it
Now has taught at Harvard, Boston College, WSSU, Ohio University , you never know where it will take you
Sounds like you have the knowledge, now to get paid " well " for it

 

[XWrench3]

As I see it. there are 2 main problems. 1) is remapping the engine control module to accommodate whatever mods you could make (turbo, cams, headers, etc.. and 2) making more heat in the cylinder head/valve area, could be enough to loosen the valve seats. if it drops a seat, say goodbye to the engine.

 

[tommudd]

and since cams would need to be custom ground, for a turbo, new pistons to start with
and remapping the computer you're looking at 1000s of bucks

 

[XWrench3]

yes, i know. i think turbo would be the most economical. but the ecm would still need to be done. and i have no clue what or where to have that done. anything can be done with enough $$$$. but i think in this case, he would be way better off with a vehicle with a good 300ish hp v-8.

 

[tommudd]

yes, i know. i think turbo would be the most economical. but the ecm would still need to be done. and i have no clue what or where to have that done. anything can be done with enough $$$$. but i think in this case, he would be way better off with a vehicle with a good 300ish hp v-8.

Can't run a turbo with the stock pistons though, custom pistons- big bucks

 

[Buck Steele]

No matter in town on a rocky course 4.10s do way better
I have them in two of my KJs and made a world of difference in both
Pulling hills , towing trailers, or just cruising , way better

Yes, especially since the tires are oversized by about 2.6" in diameter. Good call.

 

[Buck Steele]

Go for it, become a Professor , my wife is a Professor at a University in North Carolina
she started teaching, helping other Professors , doing the grunt work as she calls it
Now has taught at Harvard, Boston College, WSSU, Ohio University , you never know where it will take you
Sounds like you have the knowledge, now to get paid " well " for it

Thanks, Prof. Hawvawd? BC? Awesome! Take? No, Took. Past Tense. I'm a semi-retired Aerospace Engr/Mgr and Business owner. Got a line of high-end titanium solvent traps. Spent most of my career in Advanced Concepts at the Lockheed Skunk Works. F-117A, F-22 Flight Test, JASSM, Black Programs, hypersonics, that sort of stuff. Couldn't get by on a professor's salary, even tenured. Just do it for fun and to give something back, and work with the brightest kids around here.

I guess I'll need to get a new SUV with more ponies, but I love my Liberty - especially with a bit of lift, tire, and rub plates.