99+ manifold in a 98?

[ehall]

go-jeep has dyno charts and numbers on his write-up, and he shows gains

All this stuff is cooperative and cumulative, you might not notice everything right away but you will notice little bits and improvements at different times, with a net effect of increased performance. In this case, the better an engine can breathe in and out, then the less energy is consumed on maintenance waste and the more energy that is available to the wheels sooner. Deleting pulleys is another example of this--eliminate drag on the crank allows more energy to be sent to the wheels sooner, who knew.

99 intake will be a drop-in on the 96, no changes to power steering or anything

 

[julio_a]

found it, gimme a sec to see if i can get a scan, bear with me. its my first time. may 2006 issue, page 26. the main article is titled "24 cheap junkyard bargains". i was off a bit though. ack, couldnt figure out the scan deal. basically says

"earlier 4.0l engines used a more squared off, log style intake manifold that hampered flow to the outer ports, especially the #1 and #6 cylinders. beginning in '99 chrysler employed this horseshoe shaped, high flow manifold with individual runners. its said to be worth anywhere from 10hp to 25hp over the log type manifold. you may need to convert to the later power steering brackets and move a few vacuum lines, but the manifold bolts to all 4.0l engines. you can also use this manifold as a way of converting from the earlier renix style injection."

i was off a bit, they never really say for sure its worth x amount of hp.

 

[soopergoober]

I've been debating this swap for a long time now. I would love to see a dyno run on a stock engine. All the dyno charts I've been able to dig up seem to be on jeeps with mods that compliment the higher flow manifold, i.e. cams, bored throttle bodies, strokers, etc. Has anyone come across a dyno chart for this mod on an essentially stock h.o. 4.0?

 

[hubs97xj]

http://www.go.jeep-xj.info/HowtoIntakeManifold1.htm

Related thread on MallCrawlers linked in there as well (although that one had some additional porting done).

edit-oops, not stock- probably why I'd forgotten about it...

 

[99_XJ_]

I planned to have my XJ dyno'd in the spring at our career center. I don't have many after market parts. I have a Cherry Bomb straight through Glass Pack (sounds awesome), a K&N air filter, High grade ignition coil and wires and I run all synthetic lubes and oils. And I have the factory 99' (cracked) manifold. When I jump on the gas it throws you back in the seat and takes off like a rocket and sounds like some monster engine is under the hood. It gets to 0-60 very quick for being a brick with wheels. I'm very impressed with the performance with only so little aftermarket parts. Very curious to see what the numbers show on the dyno.

 

[crimsondragon]

Were the exhaust and manifold installed at the same time?

 

[VestaviaPirate]

99 intake will be a drop-in on the 96, no changes to power steering or anything

do you mean a 98? or will it be a direct bolt in for a 98 too (no moving anything, ie: steering)

so is the general consensus, that if you can pick up one for cheap, it would be worth it on a bone stock 98 4.0L?

Or are we still arguing the gains? Cause if it's 1-2 HP, it's not worth it unless there is some underlying benefit. If it's in the neighborhood of 10+ HP, I might do it. Like I said, I'm bored...

 

[gradon]

Just do it. Clean the intake and exhaust ports while you're in there.

 

[ehall]

Even if you don't see immediate gains right away it will assist future mods later. If you have one put it on.

 

[sjx40250]

I believe the practice is that long small cross section runners are used for high torque/low rpm applications. Hence the length of the runners of the Renix IMF. Equal length and total volume is important too. That latter is why TB spacers don’t improve performance because the added volume is such a small percentage of the total volume of the IMF. With this configuration you get a column of air that has a lot of momentum to drive into the combustion chamber when the valve opens.
So for hp @ high RPM you want short fat runners

 

[$700later]

you guys are so much smarter than me. i love it.

 

[VestaviaPirate]

Ok, I'm gonna do it! What is the best year? Or does it not matter as long as its 99-01 and after 0331 head? Didn't they change this mid 99?

Basically if I just look for one I should be able to tell, right?

 

[soopergoober]

If I remember correctly they only changed the exhaust ports. The intake manifold ports and mounting points should still match. Anyone want to second this thought for good measure? I'm not 100%.

 

[Tcarsten]

I have one on both my jeeps
They idle alot better
My YJ sounds like it dies at stop lights
And the XJ is the same
Not sure if the HP is any different, But i wouldn't go back.
Plus i got them for 19 dollars.

 

[VestaviaPirate]

My YJ sounds like it dies at stop lights
And the XJ is the same

I'm assuming this is a good thing. Is it because it's idling slightly lower?

 

[BenDiesel]

i put one on my renix. havent really driven it though. still working on it. wish i would have taken the time to gasket match the head and the intake. oh well ill do it when i build the 4.6 lol