B.Styles
NAXJA Forum User
- Location
- South Jersey
Rotary, I'm sure you can make on fit in there. Low cg, can make great hp. That or a 2jz, that's
a 3liter. Just think 1000hp mj.
a 3liter. Just think 1000hp mj.
Stage rally truck prep - need opinions
- Thread starter sureshot007
- Start date
alex22
NAXJA Forum User
- Location
- CT: waterbury area
For the engine:
Have the block sonic checked and see how big you can go. Some 4.0 blocks have enough meat to go up to a 4 inch bore. If the 2.5's are close to the 4.0's that may be possible, custom pistons will be necessary. Zero deck the block to decrease the squish distance. Port the head and intake, the 2.5 has a small TB, maybe a 4.0 will bolt right on? Roller rocker arms for durability. Machine the cylinder head to accept LS1 valves, they are larger and performance aftermarket ones are available. A set of beehive or dual/dampened valve spring will help to combat harmonics. Depending on budget you can go for Ti valves, retainers and keepers. Balance the rotating assembly to race spec. Use Joe Gibbs racing engine oil, its the only oil that we have ever seen make a positive effect on HP on the dyno.
As for the rest of the MJ, other than your drum brakes in the back where is the next worst thing on the truck?
Do you have a link to the sanctioning body's website for rules so we know what limits you have to work within?
Have the block sonic checked and see how big you can go. Some 4.0 blocks have enough meat to go up to a 4 inch bore. If the 2.5's are close to the 4.0's that may be possible, custom pistons will be necessary. Zero deck the block to decrease the squish distance. Port the head and intake, the 2.5 has a small TB, maybe a 4.0 will bolt right on? Roller rocker arms for durability. Machine the cylinder head to accept LS1 valves, they are larger and performance aftermarket ones are available. A set of beehive or dual/dampened valve spring will help to combat harmonics. Depending on budget you can go for Ti valves, retainers and keepers. Balance the rotating assembly to race spec. Use Joe Gibbs racing engine oil, its the only oil that we have ever seen make a positive effect on HP on the dyno.
As for the rest of the MJ, other than your drum brakes in the back where is the next worst thing on the truck?
Do you have a link to the sanctioning body's website for rules so we know what limits you have to work within?
tbburg
NAXJA Forum User
- Location
- Scottsdale AZ
You don't need a locker in back. Get a spool. It's lighter, simpler, and won't break. Figure out you maximum speed, and re-gear appropriately so your max rpm in high gear is just below redline.
The 4.0 TB will fit on the 2.5, and will help on the top end if you also get a header and open exhaust system to go with it.
There used to be a flywheel weight you could get from 4WD hardware or Quadratec to bolt onto the 2.5 flywheel to improve low end torque.
Looks like you're at stock height and staying there. A lot of the Jeepspeed stuff won't apply to you, although it looks like you do see some air. The hydraulic bumps help a lot on landings, how often do you get like that? The off-road classes usually shoot for 10-12 inches of travel. At stock height, you might have 6 or 7. The short hydro bumps are 3", so you'd about be sitting on them at ride height. 'Might cause problems.
Unless you get lots of air, or notice that you keep bottoming out, I'd forgo the bumps and spend the cash on shocks.
Look around for heavier anti-sway bars. don't use the Currie "anti-rock" bars. They're an off road bar and are actually not as stiff as the factory bar.
For the front springs, you can get lift springs and cut them down to stock ride height. The cut spring will have a higher effective spring rate then the same spring uncut, and it allows you to get the more common lift springs instead of buying a custom high rate no-lift spring.
The 4.0 TB will fit on the 2.5, and will help on the top end if you also get a header and open exhaust system to go with it.
There used to be a flywheel weight you could get from 4WD hardware or Quadratec to bolt onto the 2.5 flywheel to improve low end torque.
Looks like you're at stock height and staying there. A lot of the Jeepspeed stuff won't apply to you, although it looks like you do see some air. The hydraulic bumps help a lot on landings, how often do you get like that? The off-road classes usually shoot for 10-12 inches of travel. At stock height, you might have 6 or 7. The short hydro bumps are 3", so you'd about be sitting on them at ride height. 'Might cause problems.
Unless you get lots of air, or notice that you keep bottoming out, I'd forgo the bumps and spend the cash on shocks.
Look around for heavier anti-sway bars. don't use the Currie "anti-rock" bars. They're an off road bar and are actually not as stiff as the factory bar.
For the front springs, you can get lift springs and cut them down to stock ride height. The cut spring will have a higher effective spring rate then the same spring uncut, and it allows you to get the more common lift springs instead of buying a custom high rate no-lift spring.
Darky
NAXJA Forum User
- Location
- 29 Palms, CA
I think I recall reading that a 4.0 TB will bolt in and then you can open it all the way to 62mm if you want.
alex22
NAXJA Forum User
- Location
- CT: waterbury area
A 62mm TB on a 2.5 would be more of an ON/OFF switch than a throttle, not sure if that will be a good thing for you or not.
- Location
- Wasatch Range
Most Jeepspeed mods will have a place in Rally racing, so dig deeper. As for the power issue, does the 3 liter max displacement rule also tie you to a Jeep motor, or can you look at other mfgs?
http://doaracingengines.com/page2/page2.html
Better yet, a GM Midget 4 banger......how fast you wanna go? How much $$$ do you have?
http://www.racecar-engineering.com/allarticles/271309/more-than-half-a-v8.html
http://doaracingengines.com/page2/page2.html
Better yet, a GM Midget 4 banger......how fast you wanna go? How much $$$ do you have?
http://www.racecar-engineering.com/allarticles/271309/more-than-half-a-v8.html
Last edited:
stumpXJ
NAXJA Forum User
- Location
- Atlanta, Georgia
I dont have anything to say other than that looks like a CRAP load of fun. Awesome video clip, the dixie horns fit right in for sure.
I want to go Rally racin!
~James
I want to go Rally racin!
~James
sureshot007
NAXJA Forum User
- Location
- Kenmore, NY
Sanctioning body: http://www.rally-america.com
Engine block must be from the same manufacturer as the chassis. Now there is that gray area when dealing with manufacturer collaborations and parent companies - like can I put a hemi in there, or a 4g63 from an Eagle Talon TSI? (Not that I'd want either right now, but you get the idea).
Jumps like that are not daily occurrence on stage, but smaller yumps that get the wheels off the ground a tiny bit are. I don't think massive travel is necessary.
We are trying to keep this as a "budget build", mostly because I am poor and this is an expensive sport. It cost me $1000 just in entry fees for the last event. So boring out the motor, custom pistons, yadda yadda yadda - not going to happen on our budget. If you tell me that pistons from another motor will work in this block, and give me better compression, then that is the kind of info I am looking for. The more I can find at a junkyard, the better.
I had already pretty much settled on a spool for the rear end.
Aside from the rear drums, what's wrong with it? Well, not too much - right now it's just under powered and the suspension sucks. A tighter steering ration would be really awesome too. Oh yeah, we have the 4sp manual right now too.
As for finding the max speed on course - it's not like a road coarse where you know those sorts of things. It all depends on the conditions and the roads that they decided to use for the event that year. You are not allowed to drive them ahead of time, so you really don't have much of an idea of what you are getting into before hand. I figure that 100mph is probably way faster than I should be going on those roads
(I topped out at 70ish at the last event, but that's because the motor didn't have any more umph to it).
Thanks for the helps guys - keep the suggestions coming!
Engine block must be from the same manufacturer as the chassis. Now there is that gray area when dealing with manufacturer collaborations and parent companies - like can I put a hemi in there, or a 4g63 from an Eagle Talon TSI? (Not that I'd want either right now, but you get the idea).
Jumps like that are not daily occurrence on stage, but smaller yumps that get the wheels off the ground a tiny bit are. I don't think massive travel is necessary.
We are trying to keep this as a "budget build", mostly because I am poor and this is an expensive sport. It cost me $1000 just in entry fees for the last event. So boring out the motor, custom pistons, yadda yadda yadda - not going to happen on our budget. If you tell me that pistons from another motor will work in this block, and give me better compression, then that is the kind of info I am looking for. The more I can find at a junkyard, the better.
I had already pretty much settled on a spool for the rear end.
Aside from the rear drums, what's wrong with it? Well, not too much - right now it's just under powered and the suspension sucks. A tighter steering ration would be really awesome too. Oh yeah, we have the 4sp manual right now too.
As for finding the max speed on course - it's not like a road coarse where you know those sorts of things. It all depends on the conditions and the roads that they decided to use for the event that year. You are not allowed to drive them ahead of time, so you really don't have much of an idea of what you are getting into before hand. I figure that 100mph is probably way faster than I should be going on those roads
(I topped out at 70ish at the last event, but that's because the motor didn't have any more umph to it).Thanks for the helps guys - keep the suggestions coming!
blue95xj
<---- Brrrrrrrr!
- Location
- arnold, mo
Not gonna work, It's an 86 so chances are its either carbureted or TBI. Although he could see gains if he were to go multi-port fuel injection with the 91+ gear.
dudeinanxj
NAXJA Forum User
- Location
- Georgetown, KY
What about a DOHC 2.4L 4banger with NV1500/NSG370 tranny out of a 03-06 Wrangler?
2.4L I-4 148 cu in - 2003-2006
* 147 hp @ 5,200 RPM
* 165 ft/lbs @ 4,000 RPM
* DOHC
* 4 valves per cylinder
* Compression ratio = 9.50:1
NV1500 - 2003-2004
* 5 speed manual
* Used with 4 cyl models
* Ratios:
1st - 3.96
2nd - 2.37
3rd - 1.49
4th - 1.00
5th - 0.83
Rev - 3.54
NSG370 - 2005-2006
* 6 speed manual
* Used with both 4 cyl and 6 cyl models
* 10 spline input
* 23 spline output
* Ratios:
1st - 4.46
2nd - 2.61
3rd - 1.72
4th - 1.25
5th - 1.00
6th - 0.84
Rev - 4.06
2.4L I-4 148 cu in - 2003-2006
* 147 hp @ 5,200 RPM
* 165 ft/lbs @ 4,000 RPM
* DOHC
* 4 valves per cylinder
* Compression ratio = 9.50:1
NV1500 - 2003-2004
* 5 speed manual
* Used with 4 cyl models
* Ratios:
1st - 3.96
2nd - 2.37
3rd - 1.49
4th - 1.00
5th - 0.83
Rev - 3.54
NSG370 - 2005-2006
* 6 speed manual
* Used with both 4 cyl and 6 cyl models
* 10 spline input
* 23 spline output
* Ratios:
1st - 4.46
2nd - 2.61
3rd - 1.72
4th - 1.25
5th - 1.00
6th - 0.84
Rev - 4.06
Mike H.
NAXJA Forum User
- Location
- phoenix az
I would keep a limited slip outfit in the rear. Lockers/Spools will negitively effect steering.
I really like the Detroit TrueTrac.
Soft springs, heavy shocks, agree'd. I've run my rig pretty darn hard, and have no complaints with OME shocks as far as off the shelf shocks go.
I also agree doing something about a trans would be a giant benifit... I beileve a T5 tranny will bolt to the 2.5L, and the T5z has pretty nice set of ratios for keeping rpm up where it needs be... I wonder if Richmonds super close ratio 5spd would bolt up?
An alum. flywheel would be good... you're going to be spinning the hides on gravel easy enough as is, so the the inertia of a steel wheel is not going to be as important as if you were running slicks on a prep'd track.
Is there an electric water pump avail. for that motor?
Quality gravel tires and alum. wheels are a must.
Ditch the front sway bar durring testing... I think it'll really help stick the front end, course you may end up ditching the rear as well to get the truck balanced better.
If you were 4-wheel spin I'd say try and keep it leveled somewhat in the turns, but I think transfering the weight will help more with 2-wheel.
Good luck.
I really like the Detroit TrueTrac.
Soft springs, heavy shocks, agree'd. I've run my rig pretty darn hard, and have no complaints with OME shocks as far as off the shelf shocks go.
I also agree doing something about a trans would be a giant benifit... I beileve a T5 tranny will bolt to the 2.5L, and the T5z has pretty nice set of ratios for keeping rpm up where it needs be... I wonder if Richmonds super close ratio 5spd would bolt up?
An alum. flywheel would be good... you're going to be spinning the hides on gravel easy enough as is, so the the inertia of a steel wheel is not going to be as important as if you were running slicks on a prep'd track.
Is there an electric water pump avail. for that motor?
Quality gravel tires and alum. wheels are a must.
Ditch the front sway bar durring testing... I think it'll really help stick the front end, course you may end up ditching the rear as well to get the truck balanced better.
If you were 4-wheel spin I'd say try and keep it leveled somewhat in the turns, but I think transfering the weight will help more with 2-wheel.
Good luck.
tbburg
NAXJA Forum User
- Location
- Scottsdale AZ
'Have to disagree here. On asphalt, big difference. In dirt/gravel, it's hardly noticable. I do agree with the tru-trac. If you're going with a L.S. dif. they're probably the best out there. They come up used on EBay all the time and usually sell for $250-$300.(Nothing to wear out, so used is pretty safe with this one)
Summit has a universal elec water pump drive kit you can retrofit to any water pump. Also, ditch the engine driven fan. People report a huge difference on the 4.0s, the 2.5 would wake up even more. The fan's also a cheap mod. (all JY components)
You can try this, but all the go fast guys I've met/talked to use them.
sureshot007
NAXJA Forum User
- Location
- Kenmore, NY
So this is what I think I'm going to do before the next event:
MUST DO:
Refresh the motor we have (2.5 TBI)
Ditch the fan and get an electric fan
New (stock?) leafs in the rear
new shocks (bilstien 5150?)
brake fluid (ate super blue)
new pads/shoes (porterfield?)
new drive shaft ujoints (they rattle badly)
put some weight over the axle for bite
Dump the rear bumper and roll pan it
Would like to do:
Find a 5sp tranny
Find a rear end with 4.10s or higher
4.0 radiator
sway bars
lighter flywheel
Did I miss anything?
MUST DO:
Refresh the motor we have (2.5 TBI)
Ditch the fan and get an electric fan
New (stock?) leafs in the rear
new shocks (bilstien 5150?)
brake fluid (ate super blue)
new pads/shoes (porterfield?)
new drive shaft ujoints (they rattle badly)
put some weight over the axle for bite
Dump the rear bumper and roll pan it
Would like to do:
Find a 5sp tranny
Find a rear end with 4.10s or higher
4.0 radiator
sway bars
lighter flywheel
Did I miss anything?
Curtis gave you great advice on the rebuild. Hesco has one of the only available alum flywheels for the 4.0(dunno about the 2.5). I thought most 4 cyl standard MJs/Xjs came with the 4.10s(know I can get an axle at the local JY for ~$120). Addco makes great swaybars (certain models had beefier ones stock--country ed. maybe). Get the 10-blade e-fan from a 97+XJ.
tbburg
NAXJA Forum User
- Location
- Scottsdale AZ
Consider the Bilstien 7100s They're not a lot more expensive the the 5100s, and are rebuildable and revalvable.
Keep the rear bumper. It'll weigh more then a roll pan. Try shifting the battery to the bed
4cy TJs and YJs had 4.10s form the factory, but would have to have perches welded on to swap under the MJ. The popular swap here seems to be a Ford Explorer rear axle. It gives you an 8.8" ring gear, (a tab bigger then the Dana-44) 4.10 gears, disc brakes, and usually a limited slip dif.
sureshot007
NAXJA Forum User
- Location
- Kenmore, NY
We need to ditch the bumper because it gets caught on stuff. It hangs out too far and too low.
tbburg
NAXJA Forum User
- Location
- Scottsdale AZ
Oh,... well,...
bumper's gone.
bumper's gone.
sureshot007
NAXJA Forum User
- Location
- Kenmore, NY
Not a lot more expensive = twice as much? Is it really worth double?
blue95xj
<---- Brrrrrrrr!
- Location
- arnold, mo
The YJ should be close to a direct swap since they are spring under axle like the MJ.
stumpXJ
NAXJA Forum User
- Location
- Atlanta, Georgia
Here is a KILLER set of shocks in the SEC section for sale. This is an awesome price, and would be tits on the race truck. You would have to get a little creative on making them fit, but it could work.
http://www.naxja.org/forum/showthread.php?t=999162
~James
http://www.naxja.org/forum/showthread.php?t=999162
~James
