Programbo

From a site about the history of the WJ (I know that`s a Grand Cherokee but it`s still the same 4.0)

The redesigned WJ 1999 Grand Cherokee shared just 127 parts with its predecessor. . The spare tire was relocated from the side of the cargo compartment to under the floor to great relief of owners. The two heavy pushrod V8 engines were replaced by chrysler's first clean sheet V8 since the 1960s (SOHC aluminium heads, plastic intake), Chrysler's then-new Power Tech. Although this engine produced less torque than both previous V8s, it was lighter and got much better fuel economy and provided similar on road performance figures (the 23 gallon fuel tank was replaced with one of a 20.5 gallon capacity). The Inline 6 engine was also updated in 1999. 10 horsepower (7.5 kW) was added by redesigning the intake manifold.

Now the thing to remember is that this 10 HP is on a newer engine with all the power robbing California emissions control crap on it. Adding this intake to an older engine produces even more HP.

In case anyone missed it here is a link provided by 4Doors above where someone actually DID dyno test this intake manifold swap and proves the power gains. http://www.go.jeep-xj.info/HowtoIntakeManifold1.htm

JeepCoMJ

yup. to use a Borla header you'll have to (carefully) grind a little bit off the bottom of @ cylinder #5 right where the exhaust tube for cylinder 5 curves and comes down from the manifold to the collector. you'll also have to dimple that down tube on cylinder 5.


the best mod you can do in combination with this intake is to add a 60 or 62mm bored TB for better air flow.

I know nothing about decreased mpg in the city...it should stay roughly the same. it *may* decrease due to the increase in hp/torque and your personal enjoyment of "lead foot syndrome"

JeepCoMJ

remember not to take go-jeep's newer intake write-up as 100% fact. that's because he's in australia and being a RHD cherokee he's got alot of different bracketry etc. on his 4.0.

but the basics are 100% spot-on.

Programbo

I know..I was looking at the step-by-step photos he had and I was thinking, What the hell is all that odd looking junk?..LOL

VAXJCOUNTRY

Ok...so I have looked at that go-jeep write up like 15 times in the past two days and some how never noticed the dyno chart at the top. That pretty much says adding the intake and a spacer (meh) made him more power. Looks pretty plain to me right? Well I e-mailed a local dyno shop and explained to him that I needed to set the record on something for the Jeep community at large and asked for their help in the form of a reduced dyno rate so I could do some testing. If I get a good enough deal look for me to post my own results on the fuel economy and power changes made from this mod and this mod alone. My jeep is almost 100% stock. It has 150k on the clock and a recent all Mopar tune up and a good cleaning with seafoam. Its a great piece for a 97 stock baseline. I get 11/14/19 for fuel economy all the time.

VAXJCOUNTRY

Just got a response from him. Unlimited runs for 2 hours for $100...Not sure it is worth that to me. Might just do 1/8 mile runs or something...

The Black

I have a 97 and had the swap done to mine. It bolted right up according to my engine builder. I have a borla header. More power, I think so. Need to regear though.

VAXJCOUNTRY

That dyno sheet at the top of the go-jeep article is a dyno sheet for his vehicle right? The power numbers look about right.

Chumperdink

Hello gents, I am waiting on my 99+ intake manifold to come in so I can swap it onto my 98 cherokee sport. Can anyone who has done this already give me some information on any modifacations they did to fit the sucker in there right. From what I gather I will need a new gasket, and also have to extend the vacuum lines (that should be pretty much it I assume). I do not know what to extend the lines with. If you guys could just tell me what to use and where I can get it from I would appreciate it. Unless it is just called a vaccuum hose lol. Also the diameter I should get will help. I greatly appreciate any help. Thanks

JeepCoMJ

what did you do to make the borla fit with the intake?

if nothing, then your intake manifold isn't seated down 100%, and is leaking.

The Black

I did nothing to make it fit. I am not a mechanic that is why I took my jeep here

http://www.scrogginsmachine.com/

On a drunk friday night I can outsmart dumb blonds but they might win a engine building contest with me. If it is not seated down 100% what would be the problems that would show up? What would I have to do to fix said problem? Before I took my jeep to get the work done I reserached alot and I don't remember reading anything about it not bolting up with the borla header and as stated before ScrogginsMaching told me they did not have any problems with it.

gully369

When I did this swap with the Doug Thorley header from Kolak I did not have to dimple the header so the ceramic coating is still in great shape. I also ground down some of the ***** in the header and flow matched the gasket. Everything seated down great but it was still a PITA torquing down the bolt underneath.

JeepCoMJ

well, considering that the borla does not match the number 5 intake port, the manifold will crack, or simply not seat down, causing an intake/exhaust leak (leaking fuel etc.). of course, I'm using a 1998 and prior xj borla header....and I'm not aware of a late '99 and newer borla header being available.

Bustedback

I just want to do the swap to the 99+ intake because it's something to do on my ZJ.

airplanekid333

My question is will this intake manifold swap work on a '87 renix wagoneer? I have the old throttle body with a different mount then the newer ones. Many sources say its just an easy bolt on project for '96+. From what I have seen so far I don't think it would work on the 87.