Stroker in 2002 WJ...

[cmcb15]

Hello all,

I have searched for as much info on this question as I could and haven't really found anything that answers it. What will I have to do to put a stroker in my WJ with an OBDII computer to like it? I have a 2002 Jeep Grand Cherokee 4.0L that I would really like more power in for towing/hauling/wheeling. I love my Jeep and wouldn't think of getting something else so I am shopping around for options and ideas on what to do. I am an avid gear head so building a motor, etc. would not be a problem. I really don't want to go the forced induction route yet so I am looking into doing a stroker. I would build a stroker to match mostly stock compression ratio's for tunability issues. Any experience or advice would be greatly appreciated! Thanks for the help. I am very happy to be a part of this forum which has helped with almost all of my previous questions.

Dom

[RAPTORFAN85]

As long as you get bigger injectors to match the engine displacment, the computer won't know that it's a 4.6 not a 4.0 so the stock computer will work.
you may need some other things like an adjustable MAP sensor for tuning purposes, but the less you change the specs on the engine the better the stock computer will work. The closer to the stock perameters the better.

I am sure some one else will chime in with more info (and brains) than me!

[SilverXJ]

You will also want to get rid of the 0331 head and replace with a 0630, 7120 or the Alabama Cylinder head 0331, as the 0331 are prone to cracking.

[Shark]

You will also want to get rid of the 0331 head and replace with a 0630, 7120 or the Alabama Cylinder head 0331, as the 0331 are prone to cracking.

what do you mean by the "alabama cylinder head 0331"?

[RAPTORFAN85]

You will also want to get rid of the 0331 head and replace with a 0630, 7120 or the Alabama Cylinder head 0331, as the 0331 are prone to cracking.

what do you mean by the "alabama cylinder head 0331"?

http://www.alabamacylinderhead.com/

I picked one up. Going to port and polish it for some perf. gains before i throw it on the stroker...

It's the same as the 0331 except that its reinforced in the places the 0331 cracks. suposed to be stronger then the 0630 casting according to the guy I talked to on the phone. very helpfull by the way.

[Limeyjeeper]

I did a 1999 WJ in 2003 and I am doing a 1991 Comanche as we speak. I stroked the original engine and didn't try to use a different block etc. I did install a big valve head, use forged pistons, Mike leach header and bored the engine to +.060.
There are several things you need to watch out for if you are going to build a stroker from scratch.
1. The 331 Head has a different casting to enable the coil pack to be bolted to the head. A pre 99 head will give you install problems. You will need to fabricate brackets to hold the coil pack in place.
2. The exhaust manifold changed with the 0331 head as the exhaust ports are smaller. So a 630 head will require a matching exhaust manifold
3. If you want to stay with a 331 head then to overcome the cracking issue use a >2002 head
4. If you use an aftermarket camshaft you will find the camshaft end is different. The 1999 onwards camshaft end attachment is different so a pre 1999 - 2000 camshaft doesn't work unless you change the timing cover (you need a pre 99 timing cover with the hardened pin in the cover that the retaining pin touches), and use the pre 99 sprocket, retaining bolt, pin and spring.
5. You have a 43psi fuel rail with no adjustable regulator as there is no return fuel rail. Use 24lb injectors, but with the OBD11 computer tuning the stroker is a big challenge, due to the later mapping you will always struggle to balance between open and closed loop performance. Even using a map adjuster getting the setting just right takes time.
6. The intake is different so are the injector plugs. If you use many of the recommended injectors you will need to change all the injector plugs. These guys have some good info on what is what http://www.fiveomotorsport.com/Injector_SetsJEEP.asp
That is all I can remember for now.

[cmcb15]

Thanks for all the info! My biggest concern like I said earlier was tuning. I may hold off for a little while since my engine has 60,000 miles on it. I don't mind doing the stroker on a motor with such low miles as long as it's worth the time. I had heard a lot about tuning issues with the newer ECU's so thought I would ask around first. I spoke with Split Second a while back and even they said it would be hard to get good timing control with the computer. I also spoke with Avenger Superchargers and Kenne Bell yesterday. Avenger will make one work but you have to change the hood to a "Pro Stock" type hood, all said and done about $5500. Kenne Bell doesn't even offer anything for Jeep anymore and hasen't for a few years now. Limeyjeeper, how did you get your 99' WJ in tune with other than the injectors and map adjuster or was that it? Thanks again for your replies.

Dom

[RAPTORFAN85]

Thanks for all the info! My biggest concern like I said earlier was tuning. I may hold off for a little while since my engine has 60,000 miles on it. I don't mind doing the stroker on a motor with such low miles as long as it's worth the time. I had heard a lot about tuning issues with the newer ECU's so thought I would ask around first. I spoke with Split Second a while back and even they said it would be hard to get good timing control with the computer. I also spoke with Avenger Superchargers and Kenne Bell yesterday. Avenger will make one work but you have to change the hood to a "Pro Stock" type hood, all said and done about $5500. Kenne Bell doesn't even offer anything for Jeep anymore and hasen't for a few years now. Limeyjeeper, how did you get your 99' WJ in tune with other than the injectors and map adjuster or was that it? Thanks again for your replies.

Dom

If you are that worried about timing then you can just get a roller timing set with the adjustable timing.
I havnt realy heard of many that have needed to adjust timing that much unless you run realy high comp. ratio or alot of boost.

http://hescosc.com/shop.asp?action=deta ... catId=7758

pretty sure you can adjust this in 2* increments.

[Limeyjeeper]

Hi,
I must have used about 4 different sets of injectors. I found that using 24lb at 43psi injectors was the best compromise. I also mis-typed earlier the >99 fuel rail is at 49psi not 43psi. so even 24's are a little rich if you are leaving the head and cam stock. The 43psi is the pressure rating that the poundage is figured out from. You may find on a non big valve head that 22lb injectors do the trick. (I tried 22, 26, 28 and 24). Which is similar to what you need on a pre 99. There seems to be some Ford injectors available now which were not available then which flow correctly 24 or 24lb at 43psi. I had to use Accel injectors. My engine only had 30,000 miles on it when I stroked it. I ended up getting around 270hp and 350lb of torque out of it. I did get the collapsed lifter problem as others have. Today I am going to use a stock cam and 1.7 roller lifters. The cam issue is a major PITA. Never seems to happen with the factory cam. On the timing front the biggest problem is the lack of distributor. After 99 the timing/advance is completely computer controlled. An adjustable timing chain may help but the computer will either compensate of just throw a code, and pulling the front end of your engine each time you want to make an adjustment doesn't appeal to me. However using a MAP adjuster will get you to the best compromise position. Also I think using a big valve head got me to a point where the ECU simply couldn't get enough fuel in when in open loop mode which caused detonation on WOT. I saw this happen on a dyno several times. This is because in open loop the ECU is not using feedback from the sensors to adjust fuel but using pre-programmed maps which cannot be adjusted. In closed loop the ECU uses all the sensors to adjust fuel and then measure the results and make further adjustments, hence the closed loop term. I saw a supercharger a few months ago for the XJ from a company called think performance, but they seem to have dissappeared.
If you look in speed freaks on Jeeps unlimited you can lookup my old posts (same username) from that time and read a bunch of stuff.
Sorry to be so long winded but I hope this helps.

[SilverXJ]

1. The 331 Head has a different casting to enable the coil pack to be bolted to the head. A pre 99 head will give you install problems. You will need to fabricate brackets to hold the coil pack in place.

Not that much of a problem. Just use the studed bolts from the valve cover and use a bent up piece of aluminum to mount the coil.

2. The exhaust manifold changed with the 0331 head as the exhaust ports are smaller. So a 630 head will require a matching exhaust manifold

Also, if you have the cali emissions package you have to have O2 bungs welded in to the header as well as O2 sims to eliminate the after pre cat O2 sensors. Now, I have heard that after market headers for the 0331 head will work on the earlier head. I haven't verified this though.

3. If you want to stay with a 331 head then to overcome the cracking issue use a >2002 head

I heard it was 2003+

4. If you use an aftermarket camshaft you will find the camshaft end is different. The 1999 onwards camshaft end attachment is different so a pre 1999 - 2000 camshaft doesn't work unless you change the timing cover (you need a pre 99 timing cover with the hardened pin in the cover that the retaining pin touches), and use the pre 99 sprocket, retaining bolt, pin and spring.

On my 2000 it wasn't necessary to change the cover, just the cam sprocket, bolt, spring and pin.

[SilverXJ]

Hi,
After 99 the timing/advance is completely computer controlled.

AFAIK the timing on the 4.0 HO was always computer controlled. Moving the distributor didn't adjust the timing.

An adjustable timing chain may help but the computer will either compensate of just throw a code, and pulling the front end of your engine each time you want to make an adjustment doesn't appeal to me. However using a MAP adjuster will get you to the best compromise position. Also I think using a big valve head got me to a point where the ECU simply couldn't get enough fuel in when in open loop mode which caused detonation on WOT. I saw this happen on a dyno several times. This is because in open loop the ECU is not using feedback from the sensors to adjust fuel but using pre-programmed maps which cannot be adjusted. In closed loop the ECU uses all the sensors to adjust fuel and then measure the results and make further adjustments, hence the closed loop term. I saw a supercharger a few months ago for the XJ from a company called think performance, but they seem to have dissappeared.

The MAP adjuster (home made, Apexi, PSC1, etc) is what adjusts the open loop by adjusting the MAP sensor value the PCM sees. The PCM uses pre programmed maps, but it also adjusts them based on various sensors (throttle position and MAP mostly). In Closed Loop the engine can dial back the fuel using the O2 sensors mostly. For my application a simple home made map adjusted wouldn't work as it adjusts the MAP voltage over the whole RPM using one voltage. Mine was running rich at the top end and lean in the mid range. I used an Apexi to correct that as it has multiple RPM ranges to adjust. However, a PSC1 would work better.

And, yes Think Performance is no longer. Its a shame as they had a very nice package.

[cmcb15]

So in light of using different cams, valve sizes, etc., if I build a 4.5 with close to stock compression, stock valve size in an Alabama head, and the stock cam I should be okay with 22lb. injectors and an Apexi or PSC1? You mentioned O2 sims, will these still need to be required to fool the computer? I have done a lot of Chevy stroker EFI stuff and had my share of tuning issues which is why I am trying to keep things as simple as possible and still get good performance. I used to think big is better and found out the hard way that it's not! I am ready to buy everything but I just want to narrow down everything I will need first. I still know I will have the numerous trips to Autozone, etc., but at least if I can order the main parts I can figure out the little stuff (connectors, etc.) later. Thanks again!

Dom

[SilverXJ]

You may get away with 22 lb injector, may not. You will have to see.. not hard to change out. As for the O2 sims, it depends on the emissions package. The cali emissions package has 4 O2 sims and 3 cats. Two of the cats are directly after the manifold with an O2 sensor before and after them. If you go with a earlier style header and have the cali emissions package you will need to get sims for the down stream O2 sensors, as well as having two bungs welded in the header for the upstream O2 sensors. If a header for a 0331 head will work with the earlier head you don't have to worry about the O2 sensors.

[cmcb15]

I have the Cali emmissions package with a Rugged Ridge stainless header already installed so that won't change. I want to use the Alabama head if it has the mounting holes for the coil packs for ease of installation and a factory look. I wasen't sure if that's why you recommended the 02 sims or not? Will I need anything else as far as computer modification or will the adjustable map (Apexi, PSC1) be suffient? Thanks!

Dom

[RAPTORFAN85]

I have the Cali emmissions package with a Rugged Ridge stainless header already installed so that won't change. I want to use the Alabama head if it has the mounting holes for the coil packs for ease of installation and a factory look. I wasen't sure if that's why you recommended the 02 sims or not? Will I need anything else as far as computer modification or will the adjustable map (Apexi, PSC1) be suffient? Thanks!

Dom

I have the Rugged Ridge header too, and it will work with the alabama cyl. head just fine. the ports match almost exactly.
Also the Alabama cyl. head does have the mount bosses for the coil packs, another reason that I got it. You would only need the sims if you were to go with the older 0630 casting heads because you would also have to go with the older style header wich doesn't have the two down stream o2 sensors. so the sims would take the place of the actual sensors.