To Stroke Or De-Stroke?

[fastbaltss]

first I Would like to introduce myself i'm new to the forum my name is Leo. I own a 1998 Jeep Cherokee XJ Sport 5speed Manual BONE STOCK It has roughly 165,000KM on it, I am the second Owner of the vehicle. I have become quite bored with the power that it delivers, also this engine has no speed and gobs of low end torque (whichis fine) however for high speed driving the engine sounds like its really struggling. I want to build an engine that can handle high speeds, and have an equal amount of torque with it, so basically the best of both worlds but for me higher RPMS and speed is a must. So I was looking at either;

a) stroker motor + supporting upgrades which results in the best of both worlds

OR

b) de-stroke + supporting mods higher RPMS + higher speed

so I don't know what combo would work for my needs, also the parts needed to complete such work and where to get them. I can complete the work myself.

thanks

-Leo

[mendelmax]

It's an OHV engine, so whatever you'll do, you won't go much above 6000rpm, especially with agressive timing. You'd also loose the bottom end torque. To my taste, you should look for performance with stroker, to raise the torque curve through all the powerband. With additional 14% stroke, from mathematical standpoint you get at least 14% more torque and therefore 14% more power through all the powerband.
Now add extra power from additional 0.7L displacement, additional power from higher compression, from better timing etc. If you want you can get in the range of 260-280HP with no loss on daily driving properties.

[fastbaltss]

It's an OHV engine, so whatever you'll do, you won't go much above 6000rpm, especially with agressive timing. You'd also loose the bottom end torque. To my taste, you should look for performance with stroker, to raise the torque curve through all the powerband. With additional 14% stroke, from mathematical standpoint you get at least 14% more torque and therefore 14% more power through all the powerband.
Now add extra power from additional 0.7L displacement, additional power from higher compression, from better timing etc. If you want you can get in the range of 260-280HP with no loss on daily driving properties.

Hmmm... Sounds good however, say I Don't stroke and stay stock displacement and throw on a new cam, agressive timing, pistons, and supporting mods would I be in that range of speed and torque rather than just all out torque stock.

Now say, i decide to stroke 0.7L displacement will I still achieve this + supporting mods where would that take me with Horsepower vs Torque?

I am not a whole lot familiar with the 4.0L Engines soall the help is appreciated.

[mendelmax]

The only way to catch up with the stroker performance on stock displacement would be a supercharger. Because whatever you'll bolt to the engine, bolting it to the stroker will give even more gain.

[fastbaltss]

The only way to catch up with the stroker performance on stock displacement would be a supercharger. Because whatever you'll bolt to the engine, bolting it to the stroker will give even more gain.

absolutely, I don't want to supercharge im just afraid of reliability issues. I want to go N/A with this build, now I'm just wondering whether to go long-rod or short-rod, i know the long-rod offers a broad RPM range and the short-rod is subject to more tear.

Hopefully, with this stroker build i can gain a few ponies and hopefully good high RPM performance without feeling like i'm not going anywhere.

Also I'm wondering if they sell a hi-po increased air flow head for the 4.0L or maybe I just gotta get it machined.

What is the best stroker product on the market right now for the 4.0L, also what would be a good cam setup to go with it?

[John]

The only way to catch up with the stroker performance on stock displacement would be a supercharger. Because whatever you'll bolt to the engine, bolting it to the stroker will give even more gain.

Including the supercharger. But turbos and superchargers on a 4.0 will impress you with the performance gains.
John

[mendelmax]

For your application (biggest possible high end power) I'd rather choose short rods. Speaking about purely theoretical things (if I'm wrong please someone correct me)- they stay longer on the bottom of the stroke, therefore give more time for fresh mixture to enter the cylinder at the same timing. They are however less efficient at low rpm's, which still is well offset by increased stroke. But they don't give as much time on the top of the stroke for fuel to mix and evaporate well, so their efficiency in terms of fuel consumption and emissions is worse.
Long rods can give more benefit from well tuned exhaust, since they give it more time to suck the burnt gasses from the chamber. On the other hand, excessive overlap with long rods may result in sucking the fresh load to the exhaust, wasting fuel.

Many, MANY variables to consider

[fastbaltss]

For your application (biggest possible high end power) I'd rather choose short rods. Speaking about purely theoretical things (if I'm wrong please someone correct me)- they stay longer on the bottom of the stroke, therefore give more time for fresh mixture to enter the cylinder at the same timing. They are however less efficient at low rpm's, which still is well offset by increased stroke. But they don't give as much time on the top of the stroke for fuel to mix and evaporate well, so their efficiency in terms of fuel consumption and emissions is worse.
Long rods can give more benefit from well tuned exhaust, since they give it more time to suck the burnt gasses from the chamber. On the other hand, excessive overlap with long rods may result in sucking the fresh load to the exhaust, wasting fuel.

Many, MANY variables to consider

Exactly many many variables to consider! The short rod is not a bad idea at all, I will try it out, I mean i can only gain from the performance gains, I just gotta take my jeep out of commission for a while as the work is being done to it. where can i purchase these stroker kits? whose the best on the market for a 4.7 upgrade?

[mendelmax]

fastbaltss, where do you live? Do you want it to be your project for fun, or do you want an engine purely for performance? Because if you want a good engine and don't want to hassle with all the build problems, then maybe it would be a good idea to simply buy a ready stroker engine? The biggest benefit is that you don't have to disable your rig for long time, and also you know the performance it will have, since they are usually dyno tested. With proper tools, a lot of will and few beers whole engine swap is doable in one day (from early morning to night).

[fastbaltss]

fastbaltss, where do you live? Do you want it to be your project for fun, or do you want an engine purely for performance? Because if you want a good engine and don't want to hassle with all the build problems, then maybe it would be a good idea to simply buy a ready stroker engine? The biggest benefit is that you don't have to disable your rig for long time, and also you know the performance it will have, since they are usually dyno tested. With proper tools, a lot of will and few beers whole engine swap is doable in one day (from early morning to night).

I live in Canada Mendelmax, well I want to do it because im a little tired of its stock sluggish performance, that's all hopefully there are ready available strokers out there, and yes I like the idea of getting it done in one weekend or one day. hehehe if there are crate strokers available why not then? plus i will add a few performance goodies to the engine.

[mendelmax]

If 315HP and 345 ft/lbs sounds good for you, you might want to take a look: http://cgi.ebay.com/ebaymotors/TITAN-MO ... ccessories

Im not saying it's the best way to do it, especially since the opinions on Titan engines are very divided, but it has warranty, so if you're looking for performance and not for a hobby for long afternoons, then it might be worth considering. Especially since you live in Canada so simple ground shipping is possible.

[SilverXJ]

Do a search on here and Naxja for Titan engines.

A warranty is no good if the company doesn't stand behind it.

[fastbaltss]

If 315HP and 345 ft/lbs sounds good for you, you might want to take a look: http://cgi.ebay.com/ebaymotors/TITAN-MO ... ccessories

Im not saying it's the best way to do it, especially since the opinions on Titan engines are very divided, but it has warranty, so if you're looking for performance and not for a hobby for long afternoons, then it might be worth considering. Especially since you live in Canada so simple ground shipping is possible.

Wow! That's a monster of an engine hopefully this engine would prove to be as reliable as stock and for daily driving. I have no doubt that it will perform amazingly well in the snow and mud. thanks for the link.

[SilverXJ]

prove to be as reliable as stock and for daily driving.

[WarHog93]

Hey guys, I've been reading over this thread and I'm in a somewhat similar situation and have a few questions. I have a 93 YJ 4.0 with a 183k miles on it. All im running on it is a simple AIRAID throttle body spacer and Cold air intake. My primary focus for my rig is performance, mostly street with decent, albeit occasional, off road capabilities. I recently came across a Golen 4.6 stroker in a Quadratec Magazine. Aside from the future ignition, intake, and exhaust upgrades, I'm considering adding an Avenger supercharger as well. Now before i go dumping loads of cash into an old engine would it better to get the Golen swap and then add everything else? I mean i know adding a charger to a stroker would obviously yield more gains but one issue is that Avenger kits only go up to a 4.0. Would i be able to use that setup on the 4.6 or no? if not then who would i turn too for a good supercharger? Any and all feedback is appreciated