91 JY 4.0L engine rebuild/ swap - JeepForum.com
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post #1 of 4 Old 07-23-2013, 12:38 PM Thread Starter
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1991 YJ Wrangler 
Join Date: Jul 2013
Location: monroe
Posts: 1
91 JY 4.0L engine rebuild/ swap

my 91 has always been sluggish since I purchased it 7yrs ago, but recently noticeably more. I had it compression tested and found that one cylinder is completely dead. The rest are all showing around 95-100, stock specs say it should be 125-150. I have the engine out and on a stand now, Looking to rebuild it completely, or find a suitable engine in great condition. My issue is that I can't even find a good engine for it, and I am on a budget. What is my best option? Should I focus on rebuilding it, or for the sake of time and money is it better to just get a drop-in engine and go with it? I can't seem to find anybody in the area to do it for me without it being over 3,000. Any help would be greatly appreciated!

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post #2 of 4 Old 07-25-2013, 02:14 AM
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2001 TJ Wrangler 
Join Date: Jun 2003
Location: Winchester
Posts: 190
WAY easier to drop-in another engine. Then at least you'll have a spare engine to rebuild at your leisure.

That's what I'm doing right now on my 93 ZJ. My spare engine came from an 89 XJ, and I'm swapping the HO head (and accessories) onto the renix block. The only issue I've run into so-far is the crank depth is different. Easily solved with a die grinder.

2001 TJ; 1999 XJ; 1993 ZJ
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post #3 of 4 Old 08-07-2013, 03:01 AM
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1988 YJ Wrangler 
Join Date: Nov 2009
Location: Pinion Hills
Posts: 8,809
I'd try to get another motor and run it till it craps out. Could be many years from now. While you're driving your YJ save up and turn your old block into a stroker.

Adopt your pets. Don't shop for them.
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post #4 of 4 Old 08-15-2013, 07:41 PM
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1991 YJ Wrangler 
Join Date: Jan 2004
Location: landisville, pa
Posts: 20
I have a 91 and am in the middle of replacing the engine. I just bought a remanufactured long block from Promar Precision engines in NJ for $1799 shipped. It has a 3yr unlimited mileage warranty. I couldn't find any bad reviews about them unlike some of the other cheaper remanufacturers. You do have to send your old engine back to them as a core (on their dime) to enact the warranty. Also, there was no core charge up front.
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