Went from an oil change to an engine rebuild... Thoughts? Tips? - JeepForum.com

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post #1 of 5 Old 09-05-2011, 08:17 AM Thread Starter
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2008 JK Wrangler 
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Location: Morrisville, PA
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Went from an oil change to an engine rebuild... Thoughts? Tips?

I wanted to start by saying I love this forum, not sure if the wife does though .... I started out the weekend planning on doing an oil change on my 4.2 YJ.. While the oil was draining I jumped on here and saw the posts about putting the 4.0HO head on.. so then I thought.. Hmmm maybe in the near future.. Then while completeing the oil change I found metal flake. Dropped the pan to find a handful of metal shavings. the bearings and part of the timing...

So now the plan is to do a full rebuild of the engine.. I was thinking about boring out slightly , going with larger pistons while im at it... Anyone have any thoughts or suggestions to stay away from or tips as this is my first rebuild.

I have a weber 32/34 carb now and already nuttered the YJ and did the Team Rush distributer cap swap. Will this affect anything?

I picked up the 4.0 head, valvecover, and exhaust manifold today from a local salvage yard for $30, Its the 7120 head, but was off of a 95 Grand Cherokee. I was thinking about switching over to the fuel injection being I now have it with the 4.0 head, but everything I read said to put the TBI, intake, wiring from an XJ. Is the wiring and everything the same from a Grand Cheerokee?

Anyone know If I can use this as part of my rebuild. I read on here that I need a VSS adapter. I think I have the VSS from the 4.0 as well. Can this be used again? Any modifications needed to use for the 4.2?

I wanted to ask the experts out here before I get started, just trying to figure out the best combination for power, drivability and gas mileage.

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post #2 of 5 Old 09-07-2011, 02:01 PM Thread Starter
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Anyone have any experience rebuilding the 4.2? Any suggestions or precautions for a rookie? This is my first engine rebuild.
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post #3 of 5 Old 09-07-2011, 02:24 PM
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2008 JK Wrangler 
Join Date: Dec 2010
Location: Brunswick
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Ive rebuilt a few 4.0L's. A lower end rebuild kit from advance auto comes with a machined crank and matched rod/main bearings for under 200$. Use RTV on waterpump, thermostat housings, they are prone to leaking due to the pitting on the aged aluminum castings. Rebuild the oil pump and replace every seal. -Jon

NEW JK: http://www.jeepforum.com/forum/f22/its-yellow-jeep-2008-jk-1350043/

OLD YJ: http://www.jeepforum.com/forum/f22/1991-yj-project-quickie-1146445/
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post #4 of 5 Old 09-07-2011, 03:53 PM
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1990 YJ Wrangler 
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search someone JUST did this and di a write up on it I think, and there are more on here to do this as well, with complete parts breakdown, pics etc.....

Started with some rust repairs ended in a SOA...


family roll bar swap/upgrade..


1990 YJ. SOA, OME 36R 3.5" lift springs, OME 5/8 greasable shackles, OTT high steer, Custom cage, team Rush, Posi, 33 TSL swampers
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post #5 of 5 Old 09-07-2011, 09:36 PM Thread Starter
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thanks, I've done a lot of searching through the forums for a rebuild how to and haven't come across anything. If you know the link please repost it here. I will keep looking in the mean time, but didn't see anything in the yj or Cj tech sections.

thanks again
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