2.5 Power?

[dodgeb1b]

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.

[Skitzo]

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 :}

[Jeremyvnc]

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) :)

[MudDawg]

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..

[Eagle]

Originally posted by Skitzo
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 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.

[old_man]

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

[XJEEPER04]

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?

[Flowers]

Originally posted by MudDawg
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..

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

[Ghost]

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?

[old_man]

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

[Ghost]

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.

[Flowers]

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

[rockwerks]

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 :}

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.

[Ghost]

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!

[Big Al 331]

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.

[MudDawg]

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..

[Hawaiian Style]

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?

[MudDawg]

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'.

[Hawaiian Style]

3000RPM's at 60? In 5th gear? Wow, that's a huge change from what I've got now.

[Ghost]

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.

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

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?

[CheapXJ]

my MJ had this:

http://cheapxj.com/mj/mswap00.jpg

it will have this VERY soon
http://cheapxj.com/mj/mswap07.jpg

it's really not too bad of a swap, assuming you have an 87 or newer recipient for the motor.

[Big Al 331]

Is the 4.0 easier than a V8? I know it will be cheaper, depends on where I get the parts.

[Ghost]

If you have a 87 or newer. And those of us that have the 84-86 and enjoy their engine don't really have that option. It's just my opinion that with all the speed parts for the small handa and nissan and toyota crowd. it would be nice if there were companies that would cater to the jeep crowd of 4 bangers.

[Centrevillemx]

What u do is get a part for it called a "4.0 Liter" this strange part has shown to increase horsepower to around 190

[REDXJ4FUN]

Ok enough of this just swap a 4l in it. Ghost wants to know how to get a little more punch out of his 2.5. there are some nice things a about the 2.5. for one 4cly break less stuff. and its kinda good therapy when you can just stand on the gas to make a ha part of a trail yet ya dont have to wory to much.its hard to kill that 2.5 its just as tough as the 4.0.
a good cam a header and some DIY porting can realy help the little guy make some power. that along with a good intake and some 4.88 gears and you'll be quite happy. Once i get my shop built I'm going to start on a turbo 2.5 just for fun to see what i can get out of one. I've already put and avenger SC on a 2.5 and it came out nice and matcha 4.0.

[dodgeb1b]

thanks all you 4 bangers! i DONT want a 4.0, there like ass holes everyone has em'. i do like my 4 banger and it isnt bad when its up at highway speeds (80mph) i was looking at the MP cams, what do you guys think about them? also when i have the head off why not clean things up a bit? i dont need to win any races, i just want to shut mike up when i cant make it up his back yard :)
besides i have an 86, dont you have to change out the front ends to fit in the 4.0? my 2.5 is tight in there!
...I do have a fresh 400+ hp 360 in the barn... but think of the fuel bill!

[Big Al 331]

I've got a tired 318. I'm thinking of building it and putting it in inplace of my 2.5. Still thinking though.

[REDXJ4FUN]

the MP cams work pretty good and they can befound cheap on ebay.

[Big Al 331]

Anybody got numbers on the MP Cam? I can find it.

[MudDawg]

To answer Ghost... I live very near Disney...as for the info on engines...a great source are books written by the late Smokey Unich...ask questions...think about what goes on inside the engine...a little physics knowledge wouldn't hurt either.

On the quench thing...basically put, the closer you get the piston to the cylinder head around the perimeter of the combustion chamber, you increase the turbulence of the air/fuel mixture..this causes the fuel and air to be more completely mixed...the result is more power and a lower tendency to detonate (knock)..a side effect is a slight increase in compression ratio IF the engine was not originally designed with good quench in mind...most often seen in older engine designs.

Most production connecting rods are made of a iron based material..it is great for making rods used in a low RPM production engines..in cases where aftermarket forged steel rods are not available or the production cost is beyond budget..you can have your rods shotpeened...this compacts the metal making it stronger and helps eliminate stress in the metal...combined with a proper resizing of the rod and new high strenght bolts, the rod is now capable of higher RPM than when it was stock. Hesco has available rods for the 4.2 and the 4.0/2.5

[Big Al 331]

MudDAWG

What have you done to your 2.5? Need some good ideas.

[palmrose2]

Originally posted by xjnation
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.

What exactly do you use for a throttle body? I know that 88 used Renix TBI and I've looked at mine and don't think I can open it up much.

[Ghost]

Those that have chose to rib! BITE ME!

Mud Dawg,
I use to live in Vero Beach and have two uncles that live in Orlando. Thanks for the definitions. I do have a basic physics knowledge but it was in High School in the late 80's. What you say actually makes sence to me.

Palmrose2,
Old Man might chime in here. He bored a 2.5L TBI that was Renix. I have it now and hope to get it on a block soon.

I was looking at the 88 Sales brochier and it states the 2.5 has 121 HP @ 5250 RPM and 141 Lb-Ft Torque @ 3250 RPM. I know the 91 MPI engine has more HP and Torque but this is what I was going to use as a base build up motor. The TBI set up. My thinking was to get a header, the only ones I know of are pacesetter and clifford. Use the bored TBI I got from old man. Put my stage III Mopar cam in. And bigger exhaust. Maybe a 4.0L exhaust? Would that be a bad idea? And run bigger intake and exhaust valves. And bore her out some. I would like to see a 30-40% increase in power. Is this plan doable?

[palmrose2]

Originally posted by MudDawg
...cam lift is .478 with 272* duration... [/B]

Are you talking gross lift or net after putting 1.5 to 1 rockers into the equation?

Do you remember what valve springs you used?

[palmrose2]

This is it?

[Beezil]

didn't get a chance to read the whole thread, so i don't know if this has been covered or not......

try mopar's engine performance manual....I read through it a bit, and theres a ton of info in there

I gave my copy to tim flowers who will be running a 4cyl.

I'm sure you've gotten ribbing on this thread, we haven't had a good 6cyl vs 4cyl debate in a while, but you won't catch me crapping on 4cyls.....no way, not after watching sewerboss(nate) give it hell with his old one over the years.....

[MudDawg]

Sorry, been out of town...the valve lift is .478 at the stem..the springs/retainers were purchased with the cam...I chose this cam for several reasons...the duration is pretty short...the lift is not so high as to wear the springs out too quickly...what it does is allow better cylinder fill at low to medium RPM...2000 to 5000.

The object of any performance increase is to get more fuel/air into the motor and/or increase the thermal efficiency of the engine. The parts are selected depending on the use of the engine...several factors affect WHERE in the RPM band these increases occur...bearing in mind that a normally aspirated engine setup that produces power at high RPM makes less power than stock at LOW rpm...a properly mapped fuel injection system will help with the low end softness.

A ported head with stage 1 valves (properly done!!!), header...combined with a free flowing big bore exhaust (the header will do nothing if corked up with a puny exhaust...modified throttle body (if this applies) or a intake/carb combo...(injection preferred)...cam in the 270 degree range...280 range if stickshift. blueprint the lower end. Balance the rotating assembly..Have the rods shotpeened, beams polished and HP bolts installed (Hesco has rods on the shelf, sold outright) This is the short of it....but a general direction...if used strictly for high RPM racing, the components and cost go up along with the required maintenance frequency.

[Eagle]

Originally posted by palmrose2
Are you talking gross lift or net after putting 1.5 to 1 rockers into the equation?

I believe the 4.0L and 2.5L, being AMC engines, use a 1.6:1 rocker arm ratio, not 1.5:1.

[HossHoffer]

I finally got back on after a screw-up by comcast on my connection. I wanted to let you know about my 2.5l. I have the engine that Tom Houston built up. With the stage II cam and headers mated up to the heavy flywheel it makes a great engine for the trail. It also has enough spunk for the ride there. I towed a utility trailer with my camping gear up into Leadville, down the front range and over the divide (Wolf Creek Pass) and had no troubles. I think there were only a couple of times I went into 3rd gear. I'm still running my stock gearing 3:11 with 29 inch tires so even with the tall gears it was a good quick trip. In fact the headwinds were more of a problem than the inclines. I originally had the carburator on but switched to the renix tbi system even before I put Tom's engine in and that made a HUGE difference. I know that there are webber carbs for it but I was able to piece together the tbi for about $50 from the junkyard. The hardest part was splicing the wiring harness together. anyway, good luck.

[palmrose2]

OK 1.6 to 1.

My engine is pretty fresh but stock. Which means .374" at the stem. I don't really want to dive into the bottom again but I might consider redoing the top and selling an almost new head, cam and lifters. Will a different cam and head work alone make enough difference to justifie the expense?
My previous experience was with a carbed 84 and I knew that the TBI version I am now running would make more power so I didn't change anything from stock. I found that the TBI makes considerably more power than the old 84 Chief I had but still wanted more. I opened up the air intake for a gain and installed a flexalite fan with controller for a definate gain. Gains were from about 2800 rpm up.
On the exhaust side i have the OEM manifold, 2" pipe to a gutted (not by me) high flow cat and 2.25" through a muffler out the back. I figured that was enough for 2.5Ls. Am I wrong? The only headers I see advertised are made to fit a Wrangler. Will these fit the XJ?
Still would like to know of experience opening up the Renix TB.

How fast do you spin your engine MudDawg?

Great info gents.

[HossHoffer]

Clifford makes a great header and is already plumbed for O2 sensor. It does a big difference also. I opened up my renix throttle body and had better low flow and didn't lean out so bad at the top end. I didn't get more hp out of it, just better thottle response and a little better low end torque. It's free and certainly can't hurt. There is a 4bangers site that fit a 4.0 throttle body on their mpi.