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  #1  
Old July 9th, 2004, 17:50
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willy3 willy3 is offline
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intake manifold upgrade?

Hello, I am new here. I have a 91 XJ with 4.0 HO that I am working on now. I have read about replacing the intake manifold with a 99 up as it was redesigned. I understand I use my fuel rail and injectors and a power steering pump from the 99 up as well. Has anyone done this that could comment please?
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Old July 10th, 2004, 07:53
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Colorado_XJ Colorado_XJ is offline
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Re: intake manifold upgrade?

First off, welcome to the fold!

Second, I must refer you back to a similar situation recently dealt with here:

http://www.naxja.org/forum/showthread.php?t=29749

It's questioning a non-HO motor receiving a HO exhaust, but it is a similar query in that it will offer marginal gains, at best. As Eagle said, go Borla instead of busting your knuckles just to get a couple HP. It's a bucket of work to do! Time might be better spent researching the right lift/tires/accessories.

But that's just my pair of pennies.

-Rich
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Old July 10th, 2004, 13:33
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Bryan C. Bryan C. is offline
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Re: intake manifold upgrade?

I think he was referring to intake manifolds rather than exhaust manifolds. This subject has come up a number of times and there are numerous threads debating the overall efeectiveness of this upgrade.

Try this thread and the associated links for more info so you can make an informed decision about the upgrade.
http://www.naxja.org/forum/showthread.php?t=26383

Bryan
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Old July 10th, 2004, 14:03
Grizzley Grizzley is offline
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Re: intake manifold upgrade?

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

Marcus is usually around the board here unless he's running around the outback somewhere. Real good with info and returning pm's and e-mails.

Ooops, didn't check out the forum thread and this is already listed in there.
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Old July 10th, 2004, 19:42
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Colorado_XJ Colorado_XJ is offline
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Re: intake manifold upgrade?

BryanC,

Yeah, I got that. That's why I said "similar" a couple times. The situation IS similar...using a later model item to steal a couple ponies. It's a lot of headaches for something with marginal gains. If you are really jonesing for that couple more horsepower, you may as well consider removing the AC and the mechanical fan, while you are at it.

I am going to stick to my guns on this. Unless the one you have is faulty and needs replaced, strongly consider other upgrades first.

More pennies from me.

-Rich
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Old July 11th, 2004, 01:23
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Gojeep Gojeep is offline
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Re: intake manifold upgrade?

You dont swap the fuel rail at all as it is setup for a different system. You just use your old one as that has the return line you need. As for the injectors, you can use the old ones too and are better off unless you do further mods. The later injectors run at 49 psi instead of yours at 39 psi. I run the later injectors but have just ordered an adjustable fuel regulator as suggested by Dino who has the best site for this sort of information.
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Old July 11th, 2004, 12:20
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willy3 willy3 is offline
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Re: intake manifold upgrade?

Thanks for all the the input. I am still learning how to search for previously covered topics. I will try not to duplicate questions anymore. I have already installed a bored out throttle body and larger Hesco spacer, added a home made air tube with K & N cone, a complete 2 1/2 inch exhaust with free flow cat and flowmaster, an adjustable fuel pressure regulator, free flow water inlet housing and 180 degree thermostst and a GDI 3 core radiator. I am going to go ahead I think and do the intake swap and add a header at the same time.
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