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2.5 Power?

D

dodgeb1b

NAXJA Forum User
Location
Ft Irwin CA
is there any one out there that is running a built fourbanger? all i want to do is to keep up to my s10 (man thats sad, it has like 98hp) i have seen cams for the 2.5s, but i dont know how well they perform. i already took off the cat and put on a 24in glass pack (its so loud, i love it:D ) if any one has a cold air intake, id like to see some pics. what about head work? i was thinking about turboing it, but my dad wont let me. any other ideas? i dont want to run spray, its got 140K and it has to last.
 
hmm...kinda falls into the "polishing a turd" category, doesn't it? :}

can't speak for the xj, but the 2.5l in the tj was worthless...and mods were pretty worthless. i'd save up for an engine swap or a new jeep :}
 
go to a junkyard and look for a inline 6 4.0L HO engine. Those rock and you can do almost anything to them since jeep made them from late 80's to today. I'm thinking about getting a second one to have to work on and swap. I found it for $400 in great running condition. Or get an old busted up jeep xj (i found one of these for $700). Both are better than the crappy 4 banger (sorry about your luck) :)
 
The 2.5 can be made to run pretty good for it's displacement size...but the mods needed will cost a fortune if you have to pay someone to do it for you...there is no magic part that will give you a lot more power (except power adders like nitrous or a turbo), it takes an integrated approach using a combination of components and mods that compliment one another.

There is a lot of airflow volume to be found in the head, especially in the valve guide boss area. A short duration/high lift cam will help (Clifford or Hesco). Headers will help if used with a big bore exhaust system..You didn't state the year model so I can't comment on induction mods or ignition mods...mine is carburated with a conventional motorcraft distributor ignition...

I built mine as a hobby project just to see how well it would work..I most likely could have swapped out for a 4.0 cheaper..but I like a challenge..
 
Skitzo said:
hmm...kinda falls into the "polishing a turd" category, doesn't it? :}

can't speak for the xj, but the 2.5l in the tj was worthless...and mods were pretty worthless.
Click to expand...

I don't think you've been paying attention. When the Comanche was still in production and Jeep was winning all those truck races with them, those were 4-cylinder MJs they were running. That engine has a lot of potential. A performance cam would likely wake it up pretty nicely.
 
I built a pretty good running 2.5L. I ran the Renix throttle body setup, Mopar Stage III cam, Clifford headers, and inertia ring. It did OK on the highway and pulled like a mountain goat on the trails. Ghost on this board is now the proud owner of that engine. I built a 4.7L stroker and did the big swap on an 85XJ. I wouldn't recommend it unless you are a glutton for punishment. The results are staggering but so was the effort.

Tom Houston
 
well, what i would do is....take that oil leakin,loud,nutless little motor out of your jeep and drop in a 4.0 so it will run with your buddies 4.0:D(when it dont death wabble) cuase im going to smoke your @$$ on the way to moab. thats what i would do

PS what kind of work needs to be done to swap to a 4.0?
 
MudDawg said:
The 2.5 can be made to run pretty good for it's displacement size...but the mods needed will cost a fortune if you have to pay someone to do it for you...there is no magic part that will give you a lot more power (except power adders like nitrous or a turbo), it takes an integrated approach using a combination of components and mods that compliment one another.

There is a lot of airflow volume to be found in the head, especially in the valve guide boss area. A short duration/high lift cam will help (Clifford or Hesco). Headers will help if used with a big bore exhaust system..You didn't state the year model so I can't comment on induction mods or ignition mods...mine is carburated with a conventional motorcraft distributor ignition...

I built mine as a hobby project just to see how well it would work..I most likely could have swapped out for a 4.0 cheaper..but I like a challenge..
Click to expand...

MudDawg,

I have an 87 Commanche 2.5 to be built for trail only duties. Do you have any tips for a "money is no object" build up? A super charger,or NOS, will not be used! I have a cam on the way, plan to run the exhaust through the cab, pulling everything off of the engine that is not needed, relocating a Ford Ranger rad. to the bed, and other misc mods. Other than the basic BS I need to know what really works to get every ounce of power out of this engine. I have the MOPAR Perfomance engine book, but it really doesn't state anything other than, "this is what is available and these are the part numbers."

Flowers
 
I actually have the wire harness, distributer, and bored throttle bodie from old man the engine went to Hoss If I remember right. I am on a quest to do the same thing but have not started it yet. I have the Dored throttle body and a stage 3 cam. I will bore it .60 over and have the heads redone. I am still looking for the posiable stroke for this motor but it does look to be expensive to do. Which engine do you have 84-85, 86-94, or 97-up?
 
Sorry Ghost. My mind is fading fast. So, when you going to have that rig up and running? I got the stroker running and the first thing I did is pretzel the rear springs with all the torque.

Tom Houston
 
Not sure yet been bussy with other person quest. Like a sick wife that has to have a Heart Cath Friday and we did an Art Camp for kids last Saturday, and my wife's side of the family had a reunion Sunday. I hope to get started soon. I talked to a Friend that runs in the truck circuit about it this weekend, he owns a race shop localy.
 
Ghost,

I have an 87. Current plans are as stated in my previous post, plus timing gears, bored 30-60 over, cam, lifters, blah, blah, blah, blah. When you say, "have the head re-done"; what exactly do you mean? Ported and polished?

Flowers
 
can't speak for the xj, but the 2.5l in the tj was worthless...and mods were pretty worthless. i'd save up for an engine swap or a new jeep :}
Click to expand...

I run an 88 MJ 2.5 with larger throttle body and custom made exhaust.....4.10 rear gears and I stomp V6 yotas and nissans all the time.....it can be built into a killer little motor...the archer brothers won all but three SCCA sport truck races with it.
 
Skitzo,
I can speak for both the TJ and XJ 2.5L I have had both. And I know that the litle 2.5L in the TJ is a decent engine. I had a 97 that I really enjoyed and wish I still had. The only Turd was the 2.8L. The 2.5L is about as strong as it. And the current TJ engine: Wrangler SE features a 2.4-liter Power Tech I-4 engine that produces 147 horsepower and 165 pound-feet of torque
That isn't bad for a 4 banger.

Flowers,
As for the head well I was looking at the specs of the head valves in the FSM today and dreaming. The intakes are 1.9 or so and the exhaust are 1.6 or so. I was actually thinking of seeing if I could run a 2.0 intake and a 1.7 or 1.8 exhaust. And having the head cleand up. Is that what port and polished is? Cleaning out the flow chambers of the rough and harsh areas? The other idea that I have and have bounced around here is the 4 banger block that Mopar sells in their performance catalog that can be bored from 2.5-3.5L adn runs a Hemi head! But no one has been able to help me with any info on it nore what it is for. Not even the local dealer!
 
Last edited:
Here is my Turbo City/K&N set-up. It free'd up some power.

http://www.cardomain.com/member_pages/view_page.pl?page_id=336161&page=2

Hope it works.

I also have a flex fan. Used to have electric fan but found it wouldn't cool well so I took it off. The E-fan would let the engine spin up faster.:thumbup: But no joy on cooling.

I'm looking for more power too. Cat's gone, but still running muff'. It seems to be gone (no restrictions on the inside). Sound is not bad.
 
A big overbore will not add enough displacement to be of much benefit...only overbore as needed...thicker cylinder walls are stronger...the head shares valves and rockers with the 4.0...Mopar, Clifford and Hesco sell oversized valves in racing and street grade..the biggest valves that can be fitted without too much trouble are 1.94 intakes and 1.50 exhaust, with more effort 2.02 intakes and 1.60 exhaust can be fitted.. Smallblock chevy valves are around the same lenght and might be fitted as well... but if you use the large valves you need a .030 overbore to clear...porting is pretty much a case of massaging the guide bosses and blending the bowls...did a 3 angle valve job and relieved the shrouding around the valves in the combustion chamber...the block has been decked to bring the pistons to +.020 for a quench clearance of .045 when using a Felpro head gasket...cam lift is .478 with 272* duration...rods are shotpeened and have good bolts...crank turned and nitrided..rotating assembly balanced...main bearing and cylinder head studs...Clifford headers, intake and 38mm weber... the motor is streetable and has good fuel economy..
 
What auto tranny backs up the 2.5 anyway? Still the AW-4? I can imagine that a 4.0 swap would work if the tranny is the same but putting the 4.0 on the ax-5 sounds like more effort than it's worth. Might as well just drop an 8 in it if you're going to all that trouble to swap.

In a realated issue, what kind of gears are you 2.5 guys running with 33" tires? My little YJ has a hell of a time moving those bigger tires in the sand. I need some new gears, just wondering what ya'll run. 4.88's?
 
The 2.5 bellhousing pattern is unique to the 2.5, 2.8 and Iron duke..there is a 3.4 V-6 crate motor that will also fit..if you swap to a 4.0 you will need a different tranny if you use auto...the 4.0 shares the pattern with AMC V-8's.

Gears: With 4.88's and 33 Coops i run 3,000 rpm at 60mph..the motor is very happy at that speed. The difference in low range pulling power is night and day. just right for mud crawlin'.
 
Muddawg where you live n FL?

the block has been decked to bring the pistons to +.020 for a quench clearance of .045 when using a Felpro head gasket.
Click to expand...

rods are shotpeened and have good bolts...crank turned and nitrided..rotating assembly balanced...main bearing and cylinder head studs.
Click to expand...

Ok I am not an engine builder so don't laugh too hard. Is there somewhere I can read about this stuff and learn what you are talking about?
 
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