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Unread 11-12-2013, 07:10 PM   #1
kdemoney
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Join Date: Nov 2013
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89 YJ engine swap

I have an 89 YJ with the 4.2. I am new to the Jeep World. The motor I have is making some pretty bad tapping noises. I am trying to find out if it would be better to rebuild or change to an fi 4.0.

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Unread 11-12-2013, 07:17 PM   #2
Chrisnvegas
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1992 YJ Wrangler 
 
Join Date: Dec 2012
Location: Las Vegas, Nv
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It is usually customary to diagnose the source of the tapping before replacing the motor. It might not be that bad. I have heard all kind of bad noises come from a bad vibration dampener. A worn timing chain can be quite noisy too. Water pumps can make some bad sounding noises too. A worn valve train does not automatically mean motor replacement. Diagnose it first.
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Unread 11-12-2013, 07:44 PM   #3
kdemoney
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Quote:
Originally Posted by Chrisnvegas View Post
It is usually customary to diagnose the source of the tapping before replacing the motor. It might not be that bad. I have heard all kind of bad noises come from a bad vibration dampener. A worn timing chain can be quite noisy too. Water pumps can make some bad sounding noises too. A worn valve train does not automatically mean motor replacement. Diagnose it first.
My oil pressure is also dropping down next to nothing. Another reason I am considering changing the motor is for more HP. I put a 4" lift kit on with larger tires.
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Unread 11-13-2013, 06:47 AM   #4
owenb95
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1987 YJ Wrangler 
 
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Location: flemington, NJ
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Swap in the 4.0! I did it to my 87. if you are just swapping the motor and mating it to your existing tranny its a very simple swap. It's a bolt in replacement. There are a few modifications that need to be done to the bell housing but that's it. Then you need to make some fuel system improvements (fuel pump and regulator) because the 4.0 runs around 50 psi. Wiring is somewhat simple, depending on the donor motor you put in, I only needed to wire 5 wires to make my 4.0 fire up.
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1987 yj 4.2-4.0 swap AW4 & NP 242, 31inch BFG All Terrains, 2.5 in. rough country lift, Thrush header back exhaust, K&N intake, Subaru World Rally Racing Paint
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Unread 11-13-2013, 07:00 AM   #5
Que89YJ
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1989 YJ Wrangler 
 
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Location: Detroit, Michigan
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x2, find a donor XJ or YJ 91 or later and make it a MPFI.
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Unread 11-13-2013, 08:42 AM   #6
Chrisnvegas
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1992 YJ Wrangler 
 
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Location: Las Vegas, Nv
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Quote:
Originally Posted by kdemoney View Post
My oil pressure is also dropping down next to nothing. Another reason I am considering changing the motor is for more HP. I put a 4" lift kit on with larger tires.
Gotcha. I had the same problem with my (Previous) CJ7. It was the top end. Had to replace the cam, cam bearings, rockers, pivots, lifters pushrods, ect. Yes oil pressure was low from the worn cam bearings. The bottom end was fine. Ended up with a performance cam, intake, headers ect.
The 4.2 kicked butt after that. I have a 4.0 now and I still think the semi built 4.2 would have given me a run for my money.

The symptoms I had was low oil pressure and a nasty lifter tick after the engine warmed up. It was ok when first started.
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Unread 11-13-2013, 05:20 PM   #7
kdemoney
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Quote:
Originally Posted by Chrisnvegas View Post

Gotcha. I had the same problem with my (Previous) CJ7. It was the top end. Had to replace the cam, cam bearings, rockers, pivots, lifters pushrods, ect. Yes oil pressure was low from the worn cam bearings. The bottom end was fine. Ended up with a performance cam, intake, headers ect.
The 4.2 kicked butt after that. I have a 4.0 now and I still think the semi built 4.2 would have given me a run for my money.

The symptoms I had was low oil pressure and a nasty lifter tick after the engine warmed up. It was ok when first started.
It sounds like you experienced the same thing I am experiencing. I have good oil pressure and no noise when the engine is cold. I may be able to drive for 15 minutes or so before I notice the noise.
Thanks for everyone's input. I will have to way the cost of putting in a donor 4.0 or rebuilding the 4.2.
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