so how much power does your stroker have?

[philip_g]

my block is still in the machine shop.... But I've been wondering how much difference it really makes.
My 89 has 195k on it and barely has enough power to get out of it's own way. Going up a hill on the freeway? 4th gear for sure :scared:

Convince me it'll be worth my time and money :)

[stever6kid]

It depends on the stroker. I'll tell you go to thess web addresses they have loads of good info. http://www.angelfire.com/my/fan/stroker.html
http://www.jeep4.0performance.4mg.com/stroker.html
What engine do you have any ways the 4.0L, 242 or the 4.2L 258?

[Beej]

Depending on how you build it, you're gonna be looking at somewhere between 250 and 275ish...

[SBrad001]

I don't have a super fancy stroker, but I could smoke my tires for 50+ft at 2800 rpm. That was on 28" tires with stock gearing, and now I'm running 31's with 4.56s and it's even better!

Trust me, you couldn't be happier with a good stroker!

[philip_g]

It depends on the stroker. I'll tell you go to thess web addresses they have loads of good info. http://www.angelfire.com/my/fan/stroker.html
http://www.jeep4.0performance.4mg.com/stroker.html
What engine do you have any ways the 4.0L, 242 or the 4.2L 258?

I'm doing a budget job, I'm basically copying dinos.
4.0 renix I'll put a HO head and manifolds on.
258 4 weight crank I got for 50 bucks and having reground, bore the block .030 and deck it, new cam bearing and freeze plugs, nothing crazy. I'll have delta cams custom grind me a knockoff of the compcam since it's like 1/3rd the price and use their lifters.

Actually having a hard time finding a deal on pistons and rods.


I'm just having a hard time believing an extra half liter will make that much difference unless my engine is really, really tired.

[SBrad001]

. . .I'm just having a hard time believing an extra half liter will make that much difference unless my engine is really, really tired.

That .5 Liters equals 25% more displacement than a stock engine. . .conservatively that means that you should pump out ~210(more like 230+)Hp and the same goes for your torque. It's very noticable, well worth it.

[Dr. Dyno]

That .5 Liters equals 25% more displacement than a stock engine..

Not quite. If you go from 4.0 to 4.6 liters, that's a 15% gain in displacement. To gain anywhere near 15% more HP and 15% more torque, that extra displacement has to breathe in and out though a bigger straw i.e. free-flowing intake, bored TB, ported head, performance cam, header & 2.5" exhaust.

[SBrad001]

Not quite. If you go from 4.0 to 4.6 liters, that's a 15% gain in displacement. To gain anywhere near 15% more HP and 15% more torque, that extra displacement has to breathe in and out though a bigger straw i.e. free-flowing intake, bored TB, ported head, performance cam, header & 2.5" exhaust.

You're right, I'm off by a factor of two. . .I'm embarrassed.

[Quacked]

I am gathering parts to put together a 4.7 myself.

I do not know if this question has been answered before, but I know that the HO harness and computer are more aftermarket supported, tuneable and make more power. Does anyone make an engine harness to swap the engine management system from Renix to the HO set up?

If I do this will I have to swap Transmission as well?

Brad

[87manche]

I am gathering parts to put together a 4.7 myself.

I do not know if this question has been answered before, but I know that the HO harness and computer are more aftermarket supported, tuneable and make more power. Does anyone make an engine harness to swap the engine management system from Renix to the HO set up?

If I do this will I have to swap Transmission as well?

Brad
the renix system is quite adept at adapting itself.
My stroker plan involves simply upgrading the injectors and a better flowing manifold. I did not plan on touching the Renix system, with the exception of a MAP adjuster if I need to fine tune the mixture.
Because the renix system has a knock sensor it's very well suited to engine modifications, as it can retard the timing if the motor starts to ping.

[j99xj]

I've been thinking about a stroker and wondering the same things about the performance of them.

But no matter how built my stroker would be I would still be 15% lower horsepower and torque than the rest of you guys. (My elevation.)

Do you guys think I would be better off with a supercharged 4.0 as opposed to a n/a stroker?

[Dr. Dyno]

Do you guys think I would be better off with a supercharged 4.0 as opposed to a n/a stroker?

How about a supercharged stroker?
To answer your question, it all depends on the stroker build spec and all the external bolt-on performance parts that you add. I managed to eke out about 273hp/328lbft from my 4.6 stroker and although I didn't put anything exotic inside the engine, I'd maxed out on all the external bolt-ons.
A 6psi supercharged XJ 4.0 puts out about 255hp/305lbft.

[jeepinwi]

While I don't have any hard numbers, here's a real world experience comparing the 4.0 to a 4.6 stroker: My daily commute has a hill about 2 miles long which the 4.0 could keep my XJ steady at 65 mph in 5th gear and VERY slightly accelerate up the hill if I floored it. The 4.6 stroker keeps my XJ at 65 mph at roughly half throttle, and accelerating up the hill is now effortless in 5th gear.

Another example: passing on the highway required me to downshift to 4th gear for a swift pass. The stroker seems to accelerate at the same rate when in 5th gear. 4th gear acceleration is now quite fun! It pulls up to 80 mph very nicely. I have not had a chance to go more than 80 mph, but 5th gear pulls much easier at high speeds than the 4.0

Also, I only have about 500 miles on the stroker, but my 2nd tank of gas got me 19.75 mpg. I am VERY pleased with that. The 4.0 usually got me about 21 mpg, so I can live with the small increase in fuel consumption.

[philip_g]

While I don't have any hard numbers, here's a real world experience comparing the 4.0 to a 4.6 stroker: My daily commute has a hill about 2 miles long which the 4.0 could keep my XJ steady at 65 mph in 5th gear and VERY slightly accelerate up the hill if I floored it. The 4.6 stroker keeps my XJ at 65 mph at roughly half throttle, and accelerating up the hill is now effortless in 5th gear.

Another example: passing on the highway required me to downshift to 4th gear for a swift pass. The stroker seems to accelerate at the same rate when in 5th gear. 4th gear acceleration is now quite fun! It pulls up to 80 mph very nicely. I have not had a chance to go more than 80 mph, but 5th gear pulls much easier at high speeds than the 4.0

Also, I only have about 500 miles on the stroker, but my 2nd tank of gas got me 19.75 mpg. I am VERY pleased with that. The 4.0 usually got me about 21 mpg, so I can live with the small increase in fuel consumption.

thanks, that's exactly what I wanted to hear :)

[philip_g]

How about a supercharged stroker?
To answer your question, it all depends on the stroker build spec and all the external bolt-on performance parts that you add. I managed to eke out about 273hp/328lbft from my 4.6 stroker and although I didn't put anything exotic inside the engine, I'd maxed out on all the external bolt-ons.
A 6psi supercharged XJ 4.0 puts out about 255hp/305lbft.

my machinist mentioned something about setting up the block to accept some forged chevy piston and rods or other, I wasn't really paying attention since I'm focused on the budget stroker build and don't have intentions of going FI

[Pharaoh XJ]

I am thinking of a stroker too but i was told that it improves milage cause i m getting 15mpg mixed HO AW4 stock tyres so i need someone to tell if my mpg is going to get any better than 15 mpg

[Quacked]

I am surprised you are only getting 15 MPG on stock tires. I am getting that on my non-regeared 33 inch tired truck.

I wounder if you might have an O2 sensor out?

Brad

[old_man]

I might get better mileage if I could drive it like a normal adult. I get in it and I'm 16 again.

[RockMobster]

Hey guys,
New to the board. After a long string of bad luck with my 00 xj resulting in a new front end and about 5k in body and frame and paint repair, I got my baby back from the body shop put about 30 miles on it then it threw a rod. I was about ready to crush the thing i love so much, when i began to read these forums about the stroker motor. This has seemed to re kindle my love for my jeep so i have decided to put a 4.7 in. Terry at Western Engine in Denver Colorado is doing my build since I currently dont have a garage. He tells me with intake down pipe header and exhaust I can expect anywhere from 275-305 hp and more tork than necessary for any rock crawler. I'm super excited and plan to drop it in on the first of the new year. I'll post to let you know the specs.

[2drezq]

Consider doing what I did with mine:

The 17.5cc dish in the piston is 3.362" diameter (radiused at the bottom) and 0.116-0.117" deep. Since the dish is "D" shaped, if you mill it circular and increase the depth to 0.160, then the volume will be 22.6cc (23.28 minus 0.725cc for the radius). This lowers the compression back down to 9.0:1 Since the piston is 0.328" thick at the thinnest point, and we're removing 0.044", the thinnest point (dead center) will still be 0.284"

This is with the Sealed Power 677P piston. we actually went to 0.170, for a cr of 8.87:1 10K miles so far, burns 87 octane with no issues whatsoever.

I'm guessing hp is 235-245.

[Cjmartz2k]

The chevy pistons would actaully be cheaper if your block would work, but it would require a .125 overbore and that's on the harry edge. You would need to get the block sonic tested first, and then still I would worry about how thin the cylinder walls would be. Not the best option in my opinion.

As for my experience, I've only driven mine (TJ w/5 speed, 3.07's, and 31's) for one weekend after it already had about 500 miles on it, and it it was effortless cruising about 80 on the freeway with a headwind. No way I could have done that before, and I had about every bolt on/cam/tuning possible done to my old 4.0. I didn't get to race it or anything, but I was VERY happy with the highway habbits. I can't wait to get back and take it to the track and grenade a few rear axles :cheers:

[stever6kid]

Look if you guys used forged pistons it will not be a budget stroker. Go to www.summitracing.com (http://www.summitracing.com) and type in speed pro. They are hyperutectic pistons an go for about 25-30 dollars apeice. Much cheaper than forged pistons and they have sizes to fit stock, 0.030, and 0.060 bores on the XJ.

[philip_g]

The chevy pistons would actaully be cheaper if your block would work, but it would require a .125 overbore and that's on the harry edge. You would need to get the block sonic tested first, and then still I would worry about how thin the cylinder walls would be. Not the best option in my opinion.

I don't remember the specifics but I trust this machinst, he does work for about every dealer in town.

He had a dodge V10 crank in there that spun some bearings, interesting crank. Spendy too.

[philip_g]

Look if you guys used forged pistons it will not be a budget stroker. Go to www.summitracing.com (http://www.summitracing.com) and type in speed pro. They are hyperutectic pistons an go for about 25-30 dollars apeice. Much cheaper than forged pistons and they have sizes to fit stock, 0.030, and 0.060 bores on the XJ.

thanks, cheap pistons have eluded me. I see no need to go forged either.

BTW 21.39... is the price today.

[JJacobs]

Terry at Western Engine in Denver Colorado is doing my build since I currently dont have a garage. He tells me with intake down pipe header and exhaust I can expect anywhere from 275-305 hp and more tork than necessary for any rock crawler.


He's blowing smoke up your a$$, I bet it makes no more than 180 rwhp on an actual dyno (remember those things, they don't work on theory but fact?)
I've still never seen a printout from a real live dyno where a stroker makes more than 200 at the wheels. That'd be 230 wheel to get your 300 flywheel, so we keep it apples to apples.

[Quacked]

Those speed pro pistons wont work on a stroker.

THe reason for forged pistons is the relocated pins.

The wrist pin has to be moved more towards the skirt to keep compression under control.

I would say there are not enough of us wanting to make these big motors to justify the tooling expense for a manufacturer to offer a line of cast pistons.

[tealcherokee]

Those speed pro pistons wont work on a stroker.

THe reason for forged pistons is the relocated pins.

The wrist pin has to be moved more towards the skirt to keep compression under control.

I would say there are not enough of us wanting to make these big motors to justify the tooling expense for a manufacturer to offer a line of cast pistons.

or you're wrong, and you should go away.

the speed pro pistonswork fine, and a stroker can be built from 8:1 to 11:1 compression

[Blue XJ]

Those speed pro pistons wont work on a stroker.

THe reason for forged pistons is the relocated pins.

The wrist pin has to be moved more towards the skirt to keep compression under control.

I would say there are not enough of us wanting to make these big motors to justify the tooling expense for a manufacturer to offer a line of cast pistons.

They worked fine in my motor so far, its got about 4500 miles on it.

[philip_g]

They worked fine in my motor so far, its got about 4500 miles on it.
they're also all over the stroker yahoo group so I see no reason why they shouldn't work.

[philip_g]

He's blowing smoke up your a$$, I bet it makes no more than 180 rwhp on an actual dyno (remember those things, they don't work on theory but fact?)
I've still never seen a printout from a real live dyno where a stroker makes more than 200 at the wheels. That'd be 230 wheel to get your 300 flywheel, so we keep it apples to apples.

I'll be pleased with 200.
I'll have real dyno results after mine is in but I'm too cheap to do a before dyno

[Quacked]

Oops, I meant the pin needs to move towards the head of the piston.

While I am a pro mechanic I have not assembled a 4.7 stroker yet.

My experience with strokers has been relegated to a 1/4 inch and a 1/2 inch stroker flatheads in a pair of retro rods (not that black primer junk either), and a half dozen 2.3 welded cheater motors for a neighborhood dirt modified.

(I have also built several destroked 360 mopars to fit a 350 inch rule class.)

In both cases the incresed stroke caused the piston to protrude past the engine deck. The fix for this is either custom connecting rods that are shorter.

I was looking at one companies stroker kits on their website, and it showed pics of rods and pistons. I geuss I figured that either the piston or the rods were custom length.

I am really excited to be able to build a 4.7 this summer. My 4.0 is showing its 190,000 mile age and use fluids. It needs so much work that I am just building a motor.

[philip_g]

you understand that people run the 4.2 con rods with the strokers right? Hence I'm assuming no more height problem.

[tealcherokee]

Oops, I meant the pin needs to move towards the head of the piston.

While I am a pro mechanic I have not assembled a 4.7 stroker yet.

My experience with strokers has been relegated to a 1/4 inch and a 1/2 inch stroker flatheads in a pair of retro rods (not that black primer junk either), and a half dozen 2.3 welded cheater motors for a neighborhood dirt modified.

(I have also built several destroked 360 mopars to fit a 350 inch rule class.)

In both cases the incresed stroke caused the piston to protrude past the engine deck. The fix for this is either custom connecting rods that are shorter.

I was looking at one companies stroker kits on their website, and it showed pics of rods and pistons. I geuss I figured that either the piston or the rods were custom length.

I am really excited to be able to build a 4.7 this summer. My 4.0 is showing its 190,000 mile age and use fluids. It needs so much work that I am just building a motor.

no shit..... longer stroke, and the piston goes up higher.....

theres more than 1 way to change that...... as just said, shorter rods

[PapaPump]

He's blowing smoke up your a$$, I bet it makes no more than 180 rwhp on an actual dyno (remember those things, they don't work on theory but fact?)
I've still never seen a printout from a real live dyno where a stroker makes more than 200 at the wheels. That'd be 230 wheel to get your 300 flywheel, so we keep it apples to apples.


funny thing is...dynos do work on theory! have you ever looked into the development of the dyno industry? the methods used and the numbers that are spit out are all based on some arbitrary crap. they started up using drums of a size and weight that was simply enough to make the engine work hard. then they use computer programs to spit out a number that sounds about right! it's nothing like the way the OEMs test the crankshaft horsepower, but it is a good method to test for real life power gains from modifications. the big problem is that no 2 dynos spit out the same numbers all of the time for the same car. there are other factors such as temperature, fuel, etc. that change these numbers, but the fact is that dynos are just tuned to spit out relative numbers...not necessarily accurate numbers

[BlueCuda]

I would love to have built mine with the longer 4.0 rod and a custom piston but I was in a hurry. I blew my shit up and had to get it back together quick so I built a budget motor. I am not a big fan of the power band it has, its very peaky and doesn't really take off until 3000 or a little above. As mentioed before I think the longer rod would help broden the power band and make a better smoother and more powerful combo. But at a much higher cost.

[jeepinwi]

I am thinking of a stroker too but i was told that it improves milage cause i m getting 15mpg mixed HO AW4 stock tyres so i need someone to tell if my mpg is going to get any better than 15 mpg

I'm currently on my 3rd tank of gas in my stroker. I've been doing 90% highway cruising. My first tank got me 17.2 mpg, and my 2nd tank got me 19.75 mpg. I'll expect over 20 mpg from this current tank. It getting me about 1 mpg less than the 4.0 got me.

[JJacobs]

funny thing is...dynos do work on theory! have you ever looked into the development of the dyno industry?

Uh, no. The rollers accelerate quicker, it's making more power. Not hard to grasp. I leave the figures and formulas to engineers and those extracting power numbers from thin air....

[PapaPump]

it was hard to grasp though for the engineers that had to turn the feedback from those rollers into believeable and repeatable numbers...it isn't just straightforward. 1/4 mile times are probably a better gauge with a consisent driver

[JJacobs]

1/4 mile ET mostly reflects torque, launch quality, shifting and so on. The HP is reflected in the MPH.

[BLSXJ]

my stroker made more then enough power, wheich lead me to the conclusion

"there is no such thing as to much power, just not enough traction"

[Dr. Dyno]

Those speed pro pistons wont work on a stroker.

Mmmm. That's interesting. I wonder how I've managed to make my Speed Pro 677P pistons work just fine for the last 35k miles in my stroker? It must have been a fluke. :rolleyes:

He's blowing smoke up your a$$, I bet it makes no more than 180 rwhp on an actual dyno (remember those things, they don't work on theory but fact?)
I've still never seen a printout from a real live dyno where a stroker makes more than 200 at the wheels.

Then I'll dyno my strokered Jeep and be the first to break 200rwhp. Yes, I've seen others make a lot less but they all had bigger tires than stock. It also depends on the type of dyno that's used. A Mustang Dyno or a Dyno Dynamics dyno will absorb more power and show ~8% lower numbers than a Dynojet.

[Frank Z]

Interesting thread and very timely (for me at least). The one thing I was hoping to see here is a printout or attachment showing actual dyno numbers.

Anyone?

FWIW,
My stuff is at the machine shop waiting on a new set of pistons. The shop cc'd the H825CP dish volume and found that it was off by 7cc's. The spec's for the piston are 22cc's but the actual volume was 15. The 677CP had a volume of 18cc's and the pin height is .010" lower on the piston. This will bring the compression down to 9.4:1 with the other work that's been done to the block and head.

[muddshutter]

My stroker has MORE power than i could ever need.

[stever6kid]

funny thing is...dynos do work on theory! have you ever looked into the development of the dyno industry? the methods used and the numbers that are spit out are all based on some arbitrary crap. they started up using drums of a size and weight that was simply enough to make the engine work hard. then they use computer programs to spit out a number that sounds about right! it's nothing like the way the OEMs test the crankshaft horsepower, but it is a good method to test for real life power gains from modifications. the big problem is that no 2 dynos spit out the same numbers all of the time for the same car. there are other factors such as temperature, fuel, etc. that change these numbers, but the fact is that dynos are just tuned to spit out relative numbers...not necessarily accurate numbers

That's right infact most of the time you can gain afew horsepower number just by tweaking the dyno. Does it actually build up more power in your engine, NO, but the dyno will show different numbers from one run to another.

[MudDawg]

On the dyno thing....depends on what dyno, how accurate the calibration of the dyno and how accurate the peripherals are....no two pulls are the same, even back to back pulls...the conditions change...barometric pressure goes up or down, oxygen content, moisture content....hell on a chassis dyno, how tight the axle is strapped down makes a difference. When you read a dyno chart...it should show the correction factors...and even that leads to an assumed (albeit close) power output level.

In all reality, any dyno measures torque....how long it takes to accellerate a known mass relates to how much power is being produced...or in the case of a water dyno, it's the engines ability to maintain rpm against a known constant resistance.

Short rod vs long rod motors....long rod motors have less frictional losses and longer piston skirt life...short rod motors are cheaper....

However you set up the motor...quench design plays a huge part in combustion efficiency....stock rods are made of iron, not steel....careful preparation is in order to assure reliability...they are ok if properly prepped since the max revs are not all that high...personally, I would spend the extra bux and build a long rod motor.

[JJacobs]

Then I'll dyno my strokered Jeep and be the first to break 200rwhp. Yes, I've seen others make a lot less but they all had bigger tires than stock. It also depends on the type of dyno that's used. A Mustang Dyno or a Dyno Dynamics dyno will absorb more power and show ~8% lower numbers than a Dynojet.

Do it! This crowd seems almost (should I say it, oh why not) ricer-ish about dynos. "Oh, those things aren't accurate. It's not going to show my true 300Hp, so I'm not going to waste my time."

Prove me wrong, please.

[philip_g]

Do it! This crowd seems almost (should I say it, oh why not) ricer-ish about dynos. "Oh, those things aren't accurate. It's not going to show my true 300Hp, so I'm not going to waste my time."

Prove me wrong, please.

with a name like dr dyno, who can argue :)

[Dr. Dyno]

Well guys, I ran my 4.6L "poor man's" stroker on a Dastek Dyno today at MOCA Performance in Dubai. It was late in the afternoon so there was only enough time for one pull, and for some strange reason my rev-limiter was cutting in at only 4500rpm so I couldn't get a full run. The pull was done in 3rd gear of my 5-speed AX15 and the dyno applied load to the rear wheels to hold the rpm steady at 500rpm intervals to get HP/TQ readings. Here are the rear wheel numbers that I did get (STP correction):

1500rpm: 63.2hp, 221.4lbft
2000rpm: 88.1hp, 231.3lbft
2500rpm: 114.6hp, 240.8lbft
3000rpm: 141.3hp, 247.4lbft
3500rpm: 166.6hp, 250.0lbft
4000rpm: 190.4hp, 250.0lbft
4500rpm: 206???
5000rpm: ???

Peak rear wheel torque plateaued at 250lbft from 3500-4000rpm. Unfortunately I couldn't get the true HP peak but the HP curve was still climbing up to 4500rpm.
I've disconnected the battery and I'm going to leave it overnight so the ECU can reset itself. Maybe the rev-limiter will also reset so I can go above 5000rpm again.

[Frank Z]

Nice!

Hopefully I'll get my block and parts from the machine shop this week and can get my stroker assembled and installed ASAP. Dyno will have to wait till the motor is broken in though.

[philip_g]

Nice!

Hopefully I'll get my block and parts from the machine shop this week and can get my stroker assembled and installed ASAP. Dyno will have to wait till the motor is broken in though.
I'm in the same boat but don't have a cam, rods, pistons etc sourced yet either.

[JJacobs]

Not bad.. any reason they didn't do it in the industry standard, 1:1 gear ratio, which would be fourth with that trans?

[Frank Z]

I'm in the same boat but don't have a cam, rods, pistons etc sourced yet either.Have you asked your machine shop to quote the parts? You might get a better rate on the machining if you the parts from them.

FWIW, here's a link to my Stroker thread at CO4x4...

http://www.colorado4x4.org/vbb/showthread.php?t=80410

[Dr. Dyno]

Not bad.. any reason they didn't do it in the industry standard, 1:1 gear ratio, which would be fourth with that trans?

Yeah, the top speed limiter cuts in at 122mph on the speedo which is only 4350rpm in 4th gear, so that wouldn't have given me a full run to 5000rpm. As it was, I didn't get it anyway even in 3rd.
I disconnected the battery overnight to reset the ECU as per the dyno operator's suggestion. I drove the Jeep again today and the rev limiter still insists on cutting in at about 4500-4600rpm. I'm stumped and so is the dyno operator, and this is a guy who custom programs Unichips on the dyno so he knows his stuff. The engine still pulls hard and sounds happy up to 4500, there's no "check engine" light, and no fault codes.

[philip_g]

Have you asked your machine shop to quote the parts? You might get a better rate on the machining if you the parts from them.

FWIW, here's a link to my Stroker thread at CO4x4...

http://www.colorado4x4.org/vbb/showthread.php?t=80410

I told him I'd give him a crack at it.

the cam I'll get from delta, they'll custom grind a comp cams knockoff for 75 bucks with core and the lifters are something like 45 bucks so that's nice and cheap.
The rods I'll get refurbed and the pistons I'll see about getting from the machine shop, plan is to use the cheap speed pro pistons since I'm not going FI.

He also mentioned something about paying a local shop 100 bucks to pull engines for him so he doesn't have to muck with it, I might see if they'll pull my old one and swap in the new for 200 or 300 for me, as I just plain don't want to :o
Oh he's even going to cut down the crank nose for me.

The real question I have is to dish the pistons or not, and to weight match the rods and pistons or not. It's my daily so I want reliability and to keep the cost down. Just want to be able to drive up the hill out of castle rock on I25 in 5th :)

[Frank Z]

The real question I have is to dish the pistons or not, and to weight match the rods and pistons or not. It's my daily so I want reliability and to keep the cost down. Just want to be able to drive up the hill out of castle rock on I25 in 5th :)I suggest using the spread sheet at www.maxj.com (http://www.maxj.com) to get a handle on the compression ratio. Keep in mind that every block and head will require varying amounts of milling/decking inorder to get them flat. My block was sagging in the middle and needed .018" removed to get it flat. The head required .008" decking to get it flat. Six cylinder heads will sag/warp a lot easier that a v-8 head simply due to the length. (Speaking of which, I learned that storing a 6 cylinder crankshaft horizontally for a long time is not a wise move either. Keep that mutha standing tall.)

Be carefull when you have your pistons milled out. Too thin on top and the piston won't last very long.

I'm probably going a bit overboard on my motor, but then again this isn't a project I care to repeat because I took the wrong shortcuts. Yes it's possible to build a very low-buck motor and have it perform adequately, but that's not my approach this time. I'm willing to go a bit over budget and get better quality parts and hopefully a better motor in the long run.

[philip_g]

I just don't care that much, it'll be close enough. I'll slap together as is and leave the pistons stock.

[northernxj]

Do you guys gain a lot of engine noise doing the stroker build, or just gain noise from increasing exhaust flow? Thanks guys

[jeepinwi]

My stroker is nearly as quiet as the 4.0, but I'm running it through the stock exhaust still...which is a restriction for even a 4.0L. I do hear a faint valvetrain ticking most of the time due to the higher lift camshaft.

[Dr. Dyno]

Do you guys gain a lot of engine noise doing the stroker build, or just gain noise from increasing exhaust flow? Thanks guys

The engine itself shouldn't be any noisier than a 4.0 but if you use a high lift cam and stiffer valve springs, you can expect a bit of valvetrain noise at idle up to about 2000rpm.
The stock exhaust is very restrictive for a stroker but if you make it free-flowing, it shouldn't become substantially louder as long as you have a cat and a muffler that's at least as big as the stocker.

[BlueCuda]

Dynos should only be used as a tuning tool. The numbers will vary by dyno manufacturer and vary from dyno to dyno. Comparing dyno numbers accross the world is pointless IMO. The only reason I care to dyno my jeep is for AF ratios, I would like to see what it looks like. With heavy tires, 8.8 axle etc I am sure the numbers won't look great. I know my stroker makes decent HP because it runs at least as quick as a bone stock Xj but it wieghs a good 700-1klbs more.

[Bouncy]

My stroker is very quiet...sitting on the engine stand till I get time to install ;)


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Forsale: 4.2 Crank and Rods for stroker build...Also 99 Intake ported...see link for details http://www.naxja.org/forum/showthread.php?t=900424

[Dr. Dyno]

Dynos should only be used as a tuning tool. The numbers will vary by dyno manufacturer and vary from dyno to dyno. Comparing dyno numbers accross the world is pointless IMO. The only reason I care to dyno my jeep is for AF ratios, I would like to see what it looks like.

Agree that dynos are more useful as a tuning tool than anything else. They're also useful at comparing HP/TQ figures (on the same dyno) before and after doing mods. As far as using the absolute HP/TQ numbers go, you'll get variations from dyno to dyno so you can't read too much into those. What a dyno run will tell you regardless of numbers is the shape of the torque curve and at what rpm you're getting peak TQ and HP.
The Dastek Dyno that I used can work in two modes.
Firstly, It can be used as an inertia dyno where you just accelerate at WOT across the rpm range while the dyno measures the rate of acceleration, computing the TQ and then, from the engine rpm, the HP.
It can also be used as a load dyno where you hold the throttle wide open and the dyno loads the wheels to maintain a steady roller speed (and engine rpm), measuring TQ and deriving HP at various rpm in 500rpm increments. In that mode, it can be used to map the fuel and timing curves on a programmeable chip.
Dastek also manufacture the Unichip and their dyno is very useful for programming it to each individual vehicle's needs.
When I dynoed my Jeep, I found out that my air/fuel ratios were very close to the desired 13:1 at WOT so I was happy I had my MAP adjuster correctly set at 5.1v.

[JJacobs]

Dynos should only be used as a tuning tool. The numbers will vary by dyno manufacturer and vary from dyno to dyno.

That's a bunch of hooey. Barring any trickery by the dyno operator, I would think any two chassis dynos in the world should show the same vehicle to be within about 25hp. Dead even-no. Accurate enough to tell you if your combo is rocking or sucking-yes.

[BlueCuda]

Well, then there must be alot of trickery going on lol. Mustang vs Dyno Jet Vs Other all read somewhat different. May not vary by 25hp on lower HP like ours jeeps but for sure on the high numbers. Things like Torque converter stall and other things help make the numbers even less accurate. But repeatability is all your after when using a dyno to tune. Same goes for Engine Dynos as well, they all vary somewhat because of make and model and operater preferences.

Best Dyno? 1320 of smooth pavement and a wideband monitor. They can try all they want but a pair of 5000lb rollers will never match the real world.

[Dr. Dyno]

You've forgotten another reason for variation in HP/TQ numbers between dynos, and that's the HP correction factor used.
The most common are the SAE standards. The older J607 standard considers that the engine was run on a 60°F day with 0% humidity and a barometric pressure of 29.92 in-Hg, and the newer SAE J1349 standard of 77°F (25°C) day with 0% humidity and a barometric pressure of 29.234 in-Hg (99 KPa). The DIN standard commonly used in Europe corrects to a 68°F (20° C) day with 0% humidity and a barometric pressure of 29.92 in-Hg (101.3 KPa).
The resulting differences are as follows:
SAE J1349 is the most pessimistic and is currently used by US car manufacturers for their ratings.
DIN gives 3.2% higher numbers than SAE J1349.
SAE J607 (or STP) as commonly used on Westech and other engine dynos gives 4.0% higher numbers than SAE J1349.
So as you can see, the correction factors can be manipulated by unscrupulous dyno operators to produce over optimistic numbers. Likewise, a performance part manufacturer could inflate their claimed HP gains simply by applying a more generous correction factor on the dyno.
My numbers turned out to be 204rwhp@4500rpm and 250rwtq@3500-4000rpm using the STP correction. The 204rwhp isn't the true peak though because there was a glitch with my ECU that was causing the rev limiter to cut in at only 4550rpm and at that point, the HP curve was still rising.
I agree that ultimately the best place to test performance mods is on the dragstrip.