+1
A stroker is bolt-in with all the stock accessories, mounts and wiring. Any V8 will not be and will require fabrication.
Stroker Upgrade
- Thread starter rexcsmith
- Start date
+1
A stroker is bolt-in with all the stock accessories, mounts and wiring. Any V8 will not be and will require fabrication.
I went with a stroker kit from Clegg Engine and have been impressed with their service and the performance in my TJ. It came with all of the premium and balanced parts for a clean rebuild. The out the door pricing, not including the machine work, was about $2,500 for the kit, including crank, rods, pistons, cam, lifters, injectors, gaskets, etc. Machine work and ancillary parts added another thousand or so.
After break-in miles were done, I have achieved what I wanted and then some, which is almost identical to your goals. I'm running 3.73 gears on 31's with an AX-15 transmission. In the Kansas City area, there's not much in the way of rock climbing but I use it a lot at the farm, which is exclusively off road. Going to the farm is 90 miles each way and the stroker makes it enjoyable road tripping on the interstate to get there. I can also roll through the "two tracks" in the crop fields as well as gravel roads without an issue.
Good luck.
After break-in miles were done, I have achieved what I wanted and then some, which is almost identical to your goals. I'm running 3.73 gears on 31's with an AX-15 transmission. In the Kansas City area, there's not much in the way of rock climbing but I use it a lot at the farm, which is exclusively off road. Going to the farm is 90 miles each way and the stroker makes it enjoyable road tripping on the interstate to get there. I can also roll through the "two tracks" in the crop fields as well as gravel roads without an issue.
Good luck.
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I went with russ's parts. Though I went 10.2:1 cr,bigger cam and edelbrock head. Sometimes I wish I'd gone with lower compression since 91 octane isn't always available in rural areas. Octane booster and crossed fingers aren't my favorite situation.
Btw,the windstar intake i run didn't magically stop giving my motor extra hp.
I'm pretty familiar with that other forum and am myself committed to the stroker route though I'm not going to low-buck mine. I really did consider alot of options, weighed the pros and cons of each and settled on this as the best solution for me. I've re-geared to optimal gearing for my tire size and needs, done a series of bolt on mods and while it's all much better than the previous 21 years of ownership, found I still want more power specifically from 2000-4000 rpm so that I can safely pass on increasingly busy 2-lane mountain highways.
I would say there are some things that should be changed from Cheromaniac's recipe for a TJ. They are for an XJ (and an earlier one at that) and some things I don't think are mentioned.
#1 For a TJ, that cam is not optimal. Comp Cams has a cam for the thrust plate found in the TJ 4.0L motors and you'll want to go with one of those if you're going to stick with flat tappets. But the standard lift HO ones are out of stock atm. You might want the larger one anyways. If you care, I'll pull the cam numbers.
#2 You'll almost certainly need to have the donor block decked .030 -.050 to get proper quench to get good low rpm torque from higher compression and prevent pre-detonation. You need to have a good machine shop locally to do this and there are fewer and fewer around. You might also have issues with taper in your cyclinder bores from mileage and other issues that require it to be bored out a bit. You can just make the assumption that you need to go 0.030 over and have the machinist bore it out.
#3 Forged pistons are not be the best option for a NA motor. They have a different growth rate than hypereutectic pistons and tend to be noisier on cold start in a cast iron block (piston is rocking in the bore). Also Russ Potenger is in a semi-retired state these days and has been a bit hit or miss on speed of response and delivery, though people still like working with him. Clegg has good parts avialbility though and frankly good kits ready to go.
#4 Porting the head is still a good option, but you'll want the correct head for YOUR TJ, not the HO head in that list. The 0331 TUPY is prefered for later ones, but if you have a 0331 and it is not cracked by now, it's probably fine. And you probably want one of these as they support the coil rail. Also the Edelbrock Performer 4.0L head provides a bunch of advantages, but also has some disadvantages and has had some issues. You might consider it. It supports both coil rail and distributor systems.
#5 For alot of the early XJs, ODBI meant the computer could not be tuned. You do need the larger injectors to prevent going lean at WOT higher rpms, but with a TJ you can tune the engine with HPTuners. I believe all years of the TJ need an EV6 injector. There is some confusing terminology about impedance used in injectors, but EV6 is the correct type for a TJ and avoids the issue. To really get it dialed in on open loop, you'll want a wideband O2 sensor installed above the final catalytic converter in your system. Ideally you'd want it above pre-cats but it's not practical. You will likely need to adjust the basemap using WOT and the wideband in order to get startup idle, STFT and LTFT closer to target as well.
And finally, it's alot of work to do all of this, not have it dialed in properly and end up with some disappointing dyno results. Some people have seen as little as 40hp gain (but also realize the TJ has around 30% driveline losses). Yes you'll have more power with the Low buck option, but not as much as you probably expect for the amount of effort you put in. With a little more planning and work in the build these motors are able to reliably deliver 300hp, see a significant bump in low end torque and power and greatly improve drivability.
And I'd second @Rickyd that intake and exhaust improvements still matter with the stroker.
I would say there are some things that should be changed from Cheromaniac's recipe for a TJ. They are for an XJ (and an earlier one at that) and some things I don't think are mentioned.
#1 For a TJ, that cam is not optimal. Comp Cams has a cam for the thrust plate found in the TJ 4.0L motors and you'll want to go with one of those if you're going to stick with flat tappets. But the standard lift HO ones are out of stock atm. You might want the larger one anyways. If you care, I'll pull the cam numbers.
#2 You'll almost certainly need to have the donor block decked .030 -.050 to get proper quench to get good low rpm torque from higher compression and prevent pre-detonation. You need to have a good machine shop locally to do this and there are fewer and fewer around. You might also have issues with taper in your cyclinder bores from mileage and other issues that require it to be bored out a bit. You can just make the assumption that you need to go 0.030 over and have the machinist bore it out.
#3 Forged pistons are not be the best option for a NA motor. They have a different growth rate than hypereutectic pistons and tend to be noisier on cold start in a cast iron block (piston is rocking in the bore). Also Russ Potenger is in a semi-retired state these days and has been a bit hit or miss on speed of response and delivery, though people still like working with him. Clegg has good parts avialbility though and frankly good kits ready to go.
#4 Porting the head is still a good option, but you'll want the correct head for YOUR TJ, not the HO head in that list. The 0331 TUPY is prefered for later ones, but if you have a 0331 and it is not cracked by now, it's probably fine. And you probably want one of these as they support the coil rail. Also the Edelbrock Performer 4.0L head provides a bunch of advantages, but also has some disadvantages and has had some issues. You might consider it. It supports both coil rail and distributor systems.
#5 For alot of the early XJs, ODBI meant the computer could not be tuned. You do need the larger injectors to prevent going lean at WOT higher rpms, but with a TJ you can tune the engine with HPTuners. I believe all years of the TJ need an EV6 injector. There is some confusing terminology about impedance used in injectors, but EV6 is the correct type for a TJ and avoids the issue. To really get it dialed in on open loop, you'll want a wideband O2 sensor installed above the final catalytic converter in your system. Ideally you'd want it above pre-cats but it's not practical. You will likely need to adjust the basemap using WOT and the wideband in order to get startup idle, STFT and LTFT closer to target as well.
And finally, it's alot of work to do all of this, not have it dialed in properly and end up with some disappointing dyno results. Some people have seen as little as 40hp gain (but also realize the TJ has around 30% driveline losses). Yes you'll have more power with the Low buck option, but not as much as you probably expect for the amount of effort you put in. With a little more planning and work in the build these motors are able to reliably deliver 300hp, see a significant bump in low end torque and power and greatly improve drivability.
And I'd second @Rickyd that intake and exhaust improvements still matter with the stroker.
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I went with russ's parts. Though I went 10.2:1 cr,bigger cam and edelbrock head. Sometimes I wish I'd gone with lower compression since 91 octane isn't always available in rural areas. Octane booster and crossed fingers aren't my favorite situation.
Btw,the windstar intake i run didn't magically stop giving my motor extra hp.
If you've got the quench dialed at time of build, I believe with the Edelbrock head you should be able to run 87 safely with that compression ratio and a bit of adjustment to the fuel to run slightly richer in low rpm WOT scenarios where it is most dangerous. Happy to share what I've been learning in HPT with you if interested.
The nice thing about the pistons i got from russ is they are zero deck.so the head gasket sets the .043 quench. They are also an alloy with a tighter cold bore clearance than the forged pistons favored in boosted applications. No piston slap.
The main reason I can't run 87 is my high dynamic compression. I'd need a larger cam to bleed cylinder pressure.i wish I'd chose the largest of the cams russ suggested,rather than the smallest.The bright side is it has awesome low end power and fuel mileage.
Hp tuners is definitely something I need. This motor is on the edge of what a factory tune can do and leaves a lot on the table.
A larger cam and good tune are future mods that will give this motor it's full potential
And for anyone thinking they need to go find a 7120 "HO" head, the 0630 tj head has identical ports and chambers.
@GoldenGorilla what disadvantages are you reading about the eddy head?
@GoldenGorilla what disadvantages are you reading about the eddy head?
Curiosity, have you tried running plugs a few ranges colder, or moved the cam timing?
I do have a rollmaster adjustable timing set but if the timing cover comes off I'd rather it had a cam that fit the build better than to fiddle with the one in there. For context it is the same cam jezza used in his stock 4.0l dyno sessions and even he said he should have went larger and still kept street manners
The stock tune with a stock engine with stock injectors will allegedly learn and adapt to the extra air density being supplied. Changing things as drastically as you did means you aren't a good test case.
Not so much reading as from direct discussions with people building with them. I'm still leaning towards the Eddy head though for the combustion chamber, higher compression support, weight and cooling advantages.
Some springs have failed and are not deemed strong enough for the higher ramp rate with roller cams even with a mild lift that should be well within range. There have also been some failures with flat tappet cams in the higher end of their advertised supported lift. They can't just be swapped out as they aren't the stock 4.0L or LS size and some machining is needed at the seat to swap. Because they are a higher spring rate than stock they're also inversely causing some issues over time with cam lobes in some flat tappet installs. Though the last one is just a big old issue in general right now and who knows if the cam/lifter would have failed anyways. Beyond that just some machining flaws and delivery issues that you see in the aftermarket.
That wasn't what he was saying. Check out the dyno testing bolt-ons thread for the context.
I think that's a big misnomer about the tuning that it will "learn and then cancel out" any performance mods. This is not true. I don't really understand why people think the PCM works that way. The TJ does seem to be an outlier where a cold air intake can produce pretty sizeable gains, though it's not clear where the factory setup is so restrictive. There are some slight differences in the way different years work in terms of IAT sensors, but at the end of the day the engine spends most of it's time in closed loop and fueling (injector pulse width) is being adjusted by reading the upstream O2 sensor(s), intake air temp (IAT), throttle position sensor and manifold absolute pressure. It's only when pushing to wide open throttle that the engine will switch to open loop and ignore the upstream O2 and allow non-stoichiometric ratios. Technically there are partial throttle power enrichment scenarios, but normal operation is in closed loop.
But this is where a wideband O2 sensor becomes important for tuning. Without it you're flying blind as the factory narrowbands will not always be able to to give a useful reading. I had a bung welded into the pipe between the pre-cats and final cat right after it comes out under the oil pan and have it wired into my HPTuners prolink+
ie the factory O2 sensors are all pegged at 0.882V but the wideband is still giving a reading - I'd eventually go to 10.8:1. Wideband and narrowband voltages move in opposite directions.
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Early TJs use different style injector connectors. EV1 vs EV6 I think?
Unless you actually know or have even heard specifically what would cause a JTEC PCM to "learn around" a power mod, or even dyno results demonstrating it, please quit repeating that bad information. Somebody saying they think they felt something with their butt dyno one time does not constitute proof, not that most can likely even provide that. People are just repeating something they heard on the interwebz. That something is garbage.
Unless you actually know or have even heard specifically what would cause a JTEC PCM to "learn around" a power mod, or even dyno results demonstrating it, please quit repeating that bad information. Somebody saying they think they felt something with their butt dyno one time does not constitute proof, not that most can likely even provide that. People are just repeating something they heard on the interwebz. That something is garbage.
I believe you're right that all 96-98 4.0L motors have the EV1 (aka Jetronic) connector and with that you need the correct impedance style. They are not interchangeable and all TJs definitely are the high impedance type. This thread had a useful table and a ton of other useful information.
I do suspect there are errors though as my 2004 definitely has a JTEC+ PCM, not a NGC3. And really if you want to go down the stroker path with a Jeep inline 6, you should do some homework on that site. Just realize alot of time has passed since that forum started, not everything posted should be treated as gospel and there are people working with everything from early 90s XJs to 2006 TJs which all have different things going on.
I think another issue complicating the whole thing is that Jeep changed the fuel pressure and injector spec throughout production and the fuel pressure impacts the fuel volume delivery at a given pulse width. Early TJs have slightly higher than normal fuel pressure, but by the end of production it is very high specified at 58 or 59 psi as far as I've seen.
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The bare heads are recommended to start with. This is the first I'm hearing about stock valve train not working?
I was hoping that while he was doing dyno testing if bolt on mods he would have tested it after a week of driving to see.
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