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  #1  
Old July 16th, 2007, 20:28
gone postal's Avatar
gone postal gone postal is offline
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Rebuild engine or just replace??

I have a '91 XJ that basically just sits. I bought it a year ago for $600 and although it runs & drives, I wouldn't want it to be a daily driver in it's current condition.

I am considering making it my DD though so that I can park my Z28 a lil more and work on that so that it can be the hobby / weekend car that I intended it to be.

My issue is that I am an internal engine newbie. I'm fortunate that I have another vehicle so that I can take my time w/ this project, but I don't know whether I'd be best shelling out $1600 for a rebuilt engine (Ebay - 3yr unlimited mileage warranty - shipped & prepaid core shipping) or if I should undertake the rebuild myself - kits are around $450. What does a typical block boring job run? I'm sure doing it myself would be about half the cost of buying the reman., but I just have basic hand tools and having never built a motor, I just wonder if it's worth the risk. Also, how do I know what rings, etc to order? I know most jobs are .020, .030, etc over, but how do I go about finding that out? Do I just disassemble my current motor, take it to a machine shop and they'll tell me what would be best based on the current cylinder wall scarring?

Finally, I'd like to revamp the A/C too. Will parts from a '95 or '96 still fit my XJ? I want to do the R134 conversion, so I guess basically everything will have to be replaced right? I'd definitely do the compressor & accumulator, and try and do all the lines, but what about the condensor & evaporator core? I was just pricing it all out and those two parts add an extra $300+ to the job.
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  #2  
Old July 16th, 2007, 20:42
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darjevon darjevon is offline
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Re: Rebuild engine or just replace??

Almost nothing has to be replaced for r134, except components that leak, obviously. A very good quality job would be: O-rings, garter springs, compressor seals, and reciever drier. Get a professional evac, then charge it yourself with PAG-100 AC oil and a shot of dye (just in case).

If you replace the compressor, IT IS VITAL THAT YOU REPLACE IT WITH EITHER A NEW ONE THAT IS DESIGNED FOR R134a or at least a low mile working freon one that has PREVIOUSLY BEEN RUN ON FREON.

When compressors are run on freon, a weird coating forms on its surface over time that remains and continues to protect the compressor when run on r134. If a new R12-designed compressor is used, it is likely to fail early as the coating will not be present.

As for the engine, I say rebuild - these 4.0s are the about the easiest engines ever to work on. Everythings so simple - way easier than the Audis and Rovers. Too many damn sensors and vacuum lines.
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  #3  
Old July 16th, 2007, 22:30
badron badron is offline
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Re: Rebuild engine or just replace??

What does a typical block boring job run?
====================================
Best you check around. Prices can very a lot and it can very depending on how bizzy they are. I try to get my boring done in the winter. I know shops that are just begging for work in the winter and work much cheaper then to.

=======================
I just wonder if it's worth the risk.
=======================
If you never open an engine? I would get a good bud that has. Also get some books on general engine rebuilding and read them first.
In general mark everything and replace them in the same place/order you removed them. Mismatching rods and there caps have shortened or ended the life of many a rebuild.

=============================================
but I just have basic hand tools and having never built a motor,
=============================================
Rent or bum any special tools you may need. Buying tools that you will only need a few times is a waste of money to me. Or buy one or two special tool and share with buds that have others tools and WILL return then. I do this with a few good buds.

=========================
but how do I go about finding that out?
==========================

Your engine will have to be disassembled and a determination on it's fitness for rebuilding is then made. If it's even useable.
What parts would be needed would be determined at time of inspection.

====================================
Do I just disassemble my current motor
================================
Again mark with stamps everything!!!!!!!!!
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  #4  
Old July 17th, 2007, 07:37
lbsnowryder lbsnowryder is offline
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Re: Rebuild engine or just replace??

I would check a local autoparts store before i bought from ebay. I paid $1300 from shucks. You have to pay a core of $400 but you get it back later. Shucks, Checker, Kragen seemed to have the best prices available. Same deal with warranty 3 year unlimited miles. Just don't overheat it or you lose the whole warranty.

I did check into rebuilding myself and the cost of machine work and head work alone was close to shucks price on a rebuilt. Good luck
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  #5  
Old July 17th, 2007, 09:10
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avnsteve avnsteve is offline
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Re: Rebuild engine or just replace??

most of the inspection you get done at the machine shop, they will/can:

clean block and components
mic crankshaft (to determine what size bearings)
mic the cylinders (to determine what piston/rings)
and they can freshen up the head (money well spent)

but, all of that will add up in $$. If you are confident in your skills, go for it, otherwise, buy one prefab, it's really a wash when you factor in your level of self confidence in the work you do...
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  #6  
Old July 17th, 2007, 09:33
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cgmrdc cgmrdc is offline
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Re: Rebuild engine or just replace??

i bought a used engine from a salvage company for 200 with 100k miles and it runs perfectly. there is no reason to spend big for a new engine. just make some calls around your town
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  #7  
Old July 17th, 2007, 11:27
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kd5dwy kd5dwy is offline
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Re: Rebuild engine or just replace??

I just posted the A/C conversion here:

http://www.naxja.org/forum/showthread.php?t=925119

Hope that helps.
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  #8  
Old July 17th, 2007, 11:51
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98XJSport 98XJSport is offline
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Re: Rebuild engine or just replace??

Are you sure the engine needs a rebuild?
You may also look into just buying a prebuilt stroker if you are going to buy a new engine anyways.
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  #9  
Old July 17th, 2007, 12:38
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DaveKerwin DaveKerwin is offline
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Re: Rebuild engine or just replace??

replace, wait until you find the right used motor for the right price. just wait, you will find the right deal. R&R
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  #10  
Old July 17th, 2007, 12:48
75SV1 75SV1 is offline
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Re: Rebuild engine or just replace??

I am changing my A/C on a Mercedes 240D from R12 to R134. The main component that I see that needs to be changed is the condensor. The R134 seem to be parralel flow type. The other parts are the orings. The old ones are black and the new ones are a light green. I think the green ones work for either R12 or R134. The parrallel flow condensors help keep down the head pressure in the system. Also, they have more surface area for cooling. R134 isn't as efficient as R12, so it needs more surface area. The acumulator is needed to and the dryer. I'd see if an Advanced Auto or Napa has both parts for your year and a 97-2000 Cherokee and compare. See if the attachment and brackets match up. Thats kind of my plan when I get around to A/C on the Jeep. Not claiming to be an expert though.
Tom
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  #11  
Old July 17th, 2007, 15:34
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gone postal gone postal is offline
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Re: Rebuild engine or just replace??

I appreciate all of the replies.

I had considered a stroker b/c Titan motors is only 1.5hrs away from me and that's $2200, but I wasn't sure what else would be needed to complete the swap and in the end, I'd still be installing it into a 169k old vehicle - meaning the trans, TC, axles, etc are far from new. I don't want to spend an extra $600 just so that I can start breaking other parts. I only have a 3" lift and 31 A/T's and it's FL, so I don't need hill passing power or super low end grunt to roll over the next 4' boulder, etc.

Yeah, I totally forgot about the head - that's a whole extra expense that would definitely put me w/in a few hundred dollars of just buying a reman. engine. So, looks like a reman. will be the way to go for me - minimal down time too.

As for the A/C - I guess I should have prefaced that the current system was sorta working when I bought it, but then after a few weeks stopped. I bought a Freeze12 kit and when I went to use it, I found an R134 connection on my compressor - one of the add-on types. So, I'm guessing the previous owner bought a cheap "retrofit" kit from AutoZone, Wal-Mart, etc and from what I understand, if there is any R12 residue in the system, that the new R134 will combine and create a sludge/slime combo. So, I'm thinking it may be best for a fresh start. Any thoughts on this?

If I'm pulling the engine anyway, it makes sense to replace some A/C parts at the same time just b/c it'd be easy. I'm thinking new lines and such, but would all of that be necessary? If there is a sludge/slime, does everythign have to go or will the evap. & cond. stil be good?
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  #12  
Old July 17th, 2007, 17:08
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avnsteve avnsteve is offline
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Re: Rebuild engine or just replace??

when it comes to A/C, i'd go with a reputable shop, personally i prefer "small" time shops because they usually have time to sit still while you pick their brain. you can talk to a real live person, and ask the same questions you ask here, but you've got a guy there with the tools and experience in real time.
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  #13  
Old July 17th, 2007, 18:54
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1985xjlaredo 1985xjlaredo is offline
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Re: Rebuild engine or just replace??

Sounds like you should just buy a reman and be doen with it.
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