Stroking a 2.5 four cylinder?

1990XJ4x4

1990XJ4x4

NAXJA Member #1158
Location
Louisville, KY
I got a buddy with a 97 TJ that is in desperate need to get some more power from his 2.5. He took it for a swim a while back and it hasn't been the same since. so we have decided to pull the motor and really dig into it. Has anyone ever stroked one of these four cyliders and if so what kind of parts am I going to need. Any info about it or other four cylinder performance would be greatly appreciated.
 
There is no easy way to stroke the 2.5L. We can stroke the 4.0L because AMC had an entire family of I6 engines using the same basic block, and the crankshaft out of a 258 (4.2L) engine bolts right into the 4.0L, providing a longer stroke. With the 4-cyl, the 2.5L is the only engine in the "family," so there are no other cranks you can swap in. To stroke it you would have to either get a custom crank made up, or have an original crank welded up and reground with the rod journals farther offset from the crank centerline.

Last I knew there were still some Mopar Performance Stage II and Stage III cam kits available from dealers. I'd suggest one of those as a starting point for a power infusion on the 2.5L. HossHoffer is running one and can probably advise you whether or not it would require larger injectors.
 
Eagle said:
Last I knew there were still some Mopar Performance Stage II and Stage III cam kits available from dealers. I'd suggest one of those as a starting point for a power infusion on the 2.5L.
Click to expand...

Is mopar the only source for a performance cam? I looked on Crane Cams and Comp Cams websites with no luck.
 
1990XJ4x4 said:
Is mopar the only source for a performance cam? I looked on Crane Cams and Comp Cams websites with no luck.
Click to expand...
I don't know.

If you don't have a good dealer local to you, drop an e-mail to [email protected] -- put ATTN: Fran or Todd in the subject line. Ask about availability and price for these numbers:

Stage II = P4529657

Stage III = P4529658

There's also a Stage I, which is a bit more than stock but may not be worthwhile using. P4529656

These are kits, including the cam, lifters, and assembly lube.

If there are none available, I know someone who has one of the Stage III kits who might be willing to sell it. Let me know if you want me to ask him.
 
1990XJ4x4 said:
I got a buddy with a 97 TJ that is in desperate need to get some more power from his 2.5. He took it for a swim a while back and it hasn't been the same since. so we have decided to pull the motor and really dig into it. Has anyone ever stroked one of these four cyliders and if so what kind of parts am I going to need. Any info about it or other four cylinder performance would be greatly appreciated.
Click to expand...

Unfortunately a stroker cam for the 2.5 doesn't exist. There are only two ways that you can get more displacement from the 2.5. The first is to overbore the cylinders but that won't add much; the second is to tack an extra two cylinders onto the block to make it a straight six (i.e 4.0) ;).
Since you don't fancy a 4.0 swap I have an even better idea. Buy a 4.0 with tranny, TC, wiring harness, sensors, computer from a junkyard. Build the 4.0 into a 4.6L stroker and then do the swap.
Otherwise you're restricted to rebuilding the 2.5 with a Mopar (or Clifford) Performance cam and a few other external performance bolt-ons (Clifford header, exhaust, intake, 4.0 TB)
 
I am just finishing up my 2.5 engine swap on my 85 wagoneer. I just finished up on my exhaust and am very happy with my results. My old 2.5 was just to tired and going through alot of oil so decided to buy a different motor. I bought another 2.5 out of an 84 wagoneer with 80,000 on it. When I picked up the motor we tested the compression before I took it home and the first three cylinders tested at 141-143 and the fourth cylinder tested at 145. So far so good. Took it apart and put a new complete gasket set in. Cleaned the entire engine inside and out. Here is a list of new parts on the engine and all are premium parts or high flow parts for better performance:

New oil pump.
oil, temp, sending units with new guages which we ran through the firewall and mounted a set of trio guages below heater switches where vent used to be (will get some picks of guages and where in firewall I ran wires).
all new vac. lines, valves and connectors for all vac.
New sensors all the way around Costly!!
Valve cover.
Distributor, rotor, cap, plugs, wires, and coil.
Had carb cleaned and new seals
new freeze plugs.
Engine block heater off of old engine.
New mounts for engine and tranny, new shock for engine.

I use mobile1 for oil and a Baldwin oil filter. I replaced the threads on the engine to a bigger diameter to fit a larger oil filter. Now for the exhaust upgrades:

New manifold.
front pipe.
glass pack.
straight pipe.
Tailpipe.
All two inch with proper adaptors and hangers and welded also for more durability.

Cooling upgrades:

New radiator.
hoses, clamps.
electric fan instead of clutch fan.
Water pump.
160 degree thermostat and new housing.


I have done all of these mods myself except for the carb and exhaust welding and hangers. I have put on about 300 miles so far and everything runs great! My engine stays cool with the 160 thermostat and idles nice. I have a friend up here that has alot of cool equipment and he took my truck for an afternoon and gave me a spec. sheet that said that I have 114 horsepower. Which is nine better than coming from the factory new. I also should ad in that I have a three inch lift and 31.10.5 BFG all terrains and 3.73 gears. I am happy with the performance of the engine on and especially off road. I have alot more torque in 4-lo than ever!! There are other options out there for a cam upgrade and other items but decided to try it this way and see the outcome. The price on all of this came to be between 1100.00 and 1200.00. It would of been alot more if I had someone else do it. Again I am so far happy with the way things are running and the upgrades I did. I will get some pictures of some of the things that we did and post them as soon as I can. If I need more torque than I will swap out gears for a set of 4.56 or maybe higher but that won't happen until I get rid of the d35 in the rear for a crysler 8.25 or d44. Sorry this is so long but I have done alot to my woody in the past couple of weeks. If anybody has any questions let me know.


Kim. 85xjwoody.
 
Supercharger? I think I saw a kit one for the 2.5 liter motors, but I could be totally off base. You could always dig up a supercharger off of a older GM motor and fab up the brackets.

As Dyno mentioned, about all you can do is bore it. You may be lucky to see a 8-10% increase in output.

Honestly I'd start hunting for a wrecked TJ and pull the WHOLE harness from it and just use that instead of rewiring what you already have. 10x easier.
 
I have also seen on here searching that a 2.9 v6 from ford would be an easy swap for someone with the 2.5. I would stay with the 2.5 for reliability in my opinion. If you already know the engine than stay with what you know and learn more about it.
 
sintax said:
Supercharger? I think I saw a kit one for the 2.5 liter motors, but I could be totally off base.
Click to expand...

No it's not a figment of your imagination. Avenger Superchargers do have a unit for the 2.5 and that's probably the only way to extract a substantial HP/TQ gain out of the four banger.

http://www.avengersuperchargers.com/Product Info.htm
 
Ok, seeing that we can't stroke this thing out and the only big possible gain could come from a $4000 supercharger, a 4.0 swap sounds like it is becoming a logical option. Since this is a 97 am I going to have to find a 4.0 from a 97 or newer jeep (I have seen a new gen XJ in the local yard). If I do pull a 4.0 from a cherokee could it possibly bolt up to the 5-speed already in the TJ, and what kind of wiring issues am I going to have to deal with. I wish i could pull a 4.0 and transmission from a TJ, but there just arent any in the junkyards around here. Thanks for all of ya'll input on this.
 
I was talking to a local guy a few weeks ago and he was asking me if I knew anyone who was interested in a stroked 2.5. His buddy, currently deceased, had one in a circle track car that they pulled out and put a stroked Buick 4 banger in. He had a custom crank made, etc, etc, and said the thing put out over 300 hp. From what I gathered, it's in pieces needing to be assmbled and he was looking to get $1500 for it all. It has injectors, header, intake, all that good stuff. I think it even has a custom computer for it. I can try to find out more if you are interested. PM me your phone # and I'll call you.
 
My 2.5 makes somewhere in the range of 165hp....with the 33" TSL's it is almost impossible to drive it "normally" on the street...fortunately I seldom do. The motor is so peaky you either crawl leisurely up to speed or you put your foot on the floor and shift when the tach hits 6 grand. It would be a whole different story if I had shorter tires though...on the other hand... locked up in low range it does quite well...

A 300hp 2.5????.....ummmmm.....not on gasoline.....200hp maybe....but at a zillion rpm...

I asked Bennie at Hesco why they don't sell a supercharger...he said the NET gains are too low to justify the expense...

Also Hesco has all manner of internal parts including cams. You can use a double roller timing set from a 4.0...toss the original tensioner and chain guide.
 
I have been trying to stroke a 2.5 myself. No one has engineered a stroker crank for it although using the 4.2 crank as a model would seem logical. I had a shop that was going to make a billet crank for me but quoted me more than $1500 and wasn't sure if he could meet that price in the end. I've done everything you can do with my 2.5l and estimate that I am still below 150hp. Funny thing is I still take it out more than the 4.6l stroker because I get over 25mpg on the highway even with the lift and lockers. I run 4.56 gears and 33" tires. I've never got left behind on a trail except the time the front axle disconnect wouldn't lock in. If I could stroke it and get decent bang for the buck it would be done already but until someone steps up to the plate and spends the money on engineering a crank you'll have to pay a lot of money for a custom. The money is probably better spent on swapping a different drive train in.
 
HossHoffer said:
I've done everything you can do with my 2.5l and estimate that I am still below 150hp. Funny thing is I still take it out more than the 4.6l stroker because I get over 25mpg on the highway even with the lift and lockers. I run 4.56 gears and 33" tires.
Click to expand...

25 mpg? Please elaborate on what you have done to it, the guy im tryin to help out drives a lot on the highway and was considering getting rid of his jeep because of the poor mialage. This is more an effort to make him keep the Jeep than anything. That sounds like the perfect solution to me, 25 mpg, and have it driveable on the road.
 
It averages around 20 around town but I have gotten up to 30 mph on sections of a road trip. 25 mpg on the highway is pretty much what people have reported to me on this forum and about what I average. I dropped to 21-22 with 4.56 and 31s but got my mileage back with the bigger tires. It doesn't like to get good mileage if you have to cruise over 3000 rpm. As far as mods, I run a stage 3 cam, headers, tbi (from an '87), bored throttle body, and .030 over bore. Everything else is pretty much stock. I only run 2" of lift though. I think that any more lift than that will kill the mileage some.
 
I'm not familiar with the journal specs of the 2.5, but I suspect there is adequate meat to offset grind the rod journals down to get some extra stroke. Of course, then you'd need some custom sized rods and/or pistons depending on how you want to do it. Would be a good opportunity to bore the block as well anyway.

But the moral of the story I think is all this work will be for minimal gains over just swapping to a 4.0 or other larger engine.
 
You must log in or register to reply here.

Similar threads

J
NP242 assembly help
Replies
2
Views
249
Unclewolverine
U
C
Seeking Tuning Advice for Gen 1 SVT Raptor Shocks on a Jeep XJ
Replies
1
Views
179
Evan03
E
J
Down to a few electrical issues.
Replies
3
Views
308
Jay Ratliff
J
N
  • Locked
Solving lift vibrations.
Replies
0
Views
325
NAXJA_Archives
N
1
Swap from HELL!!!
Replies
2
Views
2K
1tgs2019
1
Back
Top