4.0 straight 6 to the bigger V8

EvoThree · 03-03-2009, 02:21 AM

Ok Guys first off my names jeff. Im new to this forum lol but not new to working on cars. Ok well i have a 1998 jeep grand cherokee laredo and at first the engine was sufficient for my needs but now I need to use my jeep to tow my rally car to and from races. And that little ^ has so much trouble. I was wondering if the motor mounts are the same on the Straigt 6 as the V8. and if they arnt the same is there a conversion kit I would need to get. Because the engine bay looks plenty big enough I just wanna make sure the Mounts line up. And then for you jeep gurus wud you think its worth my time and effort to switch motors or are there cheaper ways to crank out more power in these cars cheaply. I know I could get a K N cold air intake, but thats no where near enough extra power for towing. So please guys any advice is very appreciated. I know ALOT about my lil import rally car but when it comes to this jeep I dont know really how to get some more POWER! lol.
Thanks everyone
Jeff
Mitsubishi for life

440_Magnum · 03-03-2009, 09:27 AM

Quote:

Originally Posted by EvoThree

Ok Guys first off my names jeff. Im new to this forum lol but not new to working on cars. Ok well i have a 1998 jeep grand cherokee laredo and at first the engine was sufficient for my needs but now I need to use my jeep to tow my rally car to and from races. And that little ^ has so much trouble. I was wondering if the motor mounts are the same on the Straigt 6 as the V8. and if they arnt the same is there a conversion kit I would need to get. Because the engine bay looks plenty big enough I just wanna make sure the Mounts line up. And then for you jeep gurus wud you think its worth my time and effort to switch motors or are there cheaper ways to crank out more power in these cars cheaply. I know I could get a K N cold air intake, but thats no where near enough extra power for towing. So please guys any advice is very appreciated. I know ALOT about my lil import rally car but when it comes to this jeep I dont know really how to get some more POWER! lol.
Thanks everyone
Jeff
Mitsubishi for life

AFAIK, any v8 you might consider putting in will require some fabrication for mounts and an adaptor to the transmission. The AMC v8 was never made in fuel-injected form, so if you go AMC you're back to a carburetor and forget emissions testing if thats an issue in your area. The easiest thing might be a complete 5.2 engine/trans/Tcase swap from a first-gen Grand Cherokee, but it would still be a lot of work.

But IMO the bigger issues are wheelbase and weight. You don't need a ton of power to tow safely (your power/weight ratio even with a stock 4.0 is going to be a lot higher than a loaded 18-wheeler). What you DO need is enough weight and wheelbase to safely control a loaded trailer, and an XJ comes up short on both of those. I don't know how much your rally car weighs, but I'll bet the total trailer/car combo weighs about as much as the XJ, and even with trailer brakes and a good brake controller plus anti-sway hardware on the hitch, you're pushing the amount of control you can get out of a tow vehicle with such a short wheelbase.

I'm not saying it can't be done safely, but you need to look at a whole lot more than just power.

ajmorell · 03-03-2009, 09:42 AM

Quote:

Originally Posted by 440_Magnum

AFAIK, any v8 you might consider putting in will require some fabrication for mounts and an adaptor to the transmission. The AMC v8 was never made in fuel-injected form, so if you go AMC you're back to a carburetor and forget emissions testing if thats an issue in your area. The easiest thing might be a complete 5.2 engine/trans/Tcase swap from a first-gen Grand Cherokee, but it would still be a lot of work.

But IMO the bigger issues are wheelbase and weight. You don't need a ton of power to tow safely (your power/weight ratio even with a stock 4.0 is going to be a lot higher than a loaded 18-wheeler). What you DO need is enough weight and wheelbase to safely control a loaded trailer, and an XJ comes up short on both of those. I don't know how much your rally car weighs, but I'll bet the total trailer/car combo weighs about as much as the XJ, and even with trailer brakes and a good brake controller plus anti-sway hardware on the hitch, you're pushing the amount of control you can get out of a tow vehicle with such a short wheelbase.

I'm not saying it can't be done safely, but you need to look at a whole lot more than just power.

He does not have an XJ, he has a ZJ which weighs more and has a longer wheelbase than the XJ.

If you get a 98 Grand Cherokee with the v8 as a donor you can swap everything right over. Basically here is what you will need:

-Engine (the 318 and 360 were both available in 1998)
-Matching transmission
-ECU/PCM
-Wiring from v8

Your current t-case will bolt up to the v8 tranny fine although you might need to do some playing with the linkage to get it to function properly.

EvoThree · 03-03-2009, 09:54 AM

WOW thank you guys for the really good detailed help.

An regarding towing ive towed it plenty of times. no problem with controll. a little with stopping but im getting a big break set.

But as far as power it seems every little tiny hill i need to take overdrive off an ease it up the hill.

And if it does turn out to be alot of work my friend owes me alot from all the stuff Ive rebuilt on his car for him so i can have an extra set of hands. lol

And so I was kinda right, right? I basically get the V8. appropriate mounts and etc what you said. And is there different size V8s? and if so which would you reccomend? and then 1 more question how much more torque and HP will i have with the V8?

Then regarding the 4.0 6 cylinder is it at all possible or even worth upgrading it to the equivalent of the V8? And if it is upgradable what else besides a nice cold air intake should I put on to get that engine to really have more torque and HP?

Once again thank you so much guys I REALLLLLLY appreciate the help.

ajmorell · 03-03-2009, 10:04 AM

One thing I noticed, you said you have to take OD off for any hill - when towing anything (with a ZJ anyways) especially a car you should never tow with OD turned on.

If I were going to spend the time and money to do a v8 swap I would swap in the 5.9/360. There is a lot of argument on whether or not it is worth it or not. I say it depends. If you can't afford to sell your Jeep and buy another with a v8 but have the resources and time to do the swap then yes. If you have to pay someone to do it then it most certainly isn't. The v8 should have everything you are looking for in stock form but while it is out I would put some headers on it and a CAI like you mentioned.

EvoThree · 03-03-2009, 10:15 AM

well i usually have OD on on the freeway. thats all. But Yeah I can do all the work myself. ive rebuilt my engine on my rally car twice so i do have engine and transmission experience. just my friend is extra hands because I help him alot.

ajmorell · 03-03-2009, 10:21 AM

Even on the freeway I wouldn't run with OD on, it's just going to burn up the transmission

EvoThree · 03-04-2009, 01:37 AM

o ok thanks for the advice. By the way do you think there is anyway to upgrade the straight 6 for cheaper then the V8 but still have the 4.0 be powerful enough???

5-90 · 03-04-2009, 02:16 AM

Upgrade the I6? Sure - stroke it!

Score yourself a 258ci crankshaft and a set of 258ci rods. Drop the reciprocating assembly from the 242 you've got now, have the pistons and pins put on the 258ci rods, and drop the whole new reciprocating assembly in - have it done in an afternoon, if you don't need any boring done.

This should net you about a half-litre of displacement (from the increased stroke,) slightly increased compression (from the increased stroke,) and a higher torque curve that is still nice and flat to about 4000rpm. May even work better for you than the V8 swap (although, if you've got your heart set on the V8 swap, stick with an LA-block ChryCo - 318 or 360ci - since that's what the thing was designed around for a V8 anyhow. You'll require an electronics/drivetrain swap to go with all of that...)

OBD-II has a history of getting along well with strokers, but you may need to upsize your fuel injectors just a bit, so you can supply the additional fuel you'll need more efficiently. It's still easier than swapping out the whole engine and drivetrain tho - and a Hell of a lot cheaper!

jeepdaddy2000 · 03-04-2009, 05:25 AM

IF you want a V8 powered GC, you would be time and money ahead to sell what you have and buy one in stock trim. The market is soft and V8 powered rigs don't pull the numbers they once did. Most of these will have the larger 44 rear which is a plus. Find one with a factory tow package, as these will have upgraded cooling sustems.
I tend to agree with 440 magnum. The GC is marginal as a tow rig for a car/trailer combo. A heavy wind or blown trailer tire can whip a lighter tow rig right off the road. The stock brakes won't handle the heat of heavy braking well and even if you upgrade, your not going to see a lot improvement.

440_Magnum · 03-04-2009, 12:52 PM

Quote:

Originally Posted by ajmorell

He does not have an XJ, he has a ZJ which weighs more and has a longer wheelbase than the XJ.

duh. I saw the Z and my brain turned it to an X- my wife always says I make things more complicated than they should be

Yeah, that's definitely a simple swap. And the tow control issues will be significantly less, but even still the ZJ isn't really a beast of a tow vehicle. But it should handle a rally car fine.

EvoThree · 03-05-2009, 02:48 AM

how do i turn my engine into a stroker, and also what does a stroker mean?

also where would i be able to buy used or new v8 motors with the trannys would i have to buy one online or anyone know a store in southern cali that i could pick one up?

heres my number 909 213 7291 if anyone can call or text me with info, im not gonna be at the comp for a while, so please call or text me, also will have my brother check it every once in a while to keep me posted

**Cutlass327** · 03-05-2009, 07:53 AM

Stroker engines are ones that the cranks shaft has been replaced/modified to give the engine more stroke....

Quote:

Score yourself a 258ci crankshaft and a set of 258ci rods. Drop the reciprocating assembly from the 242 you've got now, have the pistons and pins put on the 258ci rods, and drop the whole new reciprocating assembly in - have it done in an afternoon, if you don't need any boring done.

chainerx · 03-05-2009, 08:21 AM

It gives the engine more torque and horsepower. There are many unofficial levels of "stroker" from relatively quick junkyards swaps all the way up to turning your 4L into a supercharged 5L.

I would consider getting a different tow rig unless you are really set on the ZJ. If that is the case buying a V8 one would be best. If you like yours for sentimental reasons, maybe you should stoke it, just for fun then it's got it's original engine too. However a stroker can be expensive and time consuming depending on what your expectations are from it. http://www.jeepstrokers.com has a lot of reading for you if you go that route.

EvoThree · 03-11-2009, 01:17 PM

thank u guys for all the info. I really appreciate it