I'm have a 2007 Unlimited X with a 3.8l, obviously, with 128000km on it. No problems yet knock on wood, and just thinking ahead. A few things i cant find any straight answers to on engine rebuilds. I know all about getting a new or used engine and swapping or conversions ect... but what about rebuilding. I've read rebuilding an engine, getting it done by a pro, is better than the ones that come out of the factory. If so what are the differences?

1) What options and parts can be replaced with higher quality ones? Assuming its a complete rebuild.

2) What kind of HP gains if any can be achieved? Reboring the cylinders making them bigger should give more power. But how much?

3) Gas mileage. What kind of gas mileage increase if any?

4) Cost. I can't find any info on this. What is a good rough estimate for a standard rebuild? Is it a $3000 job or $10000 etc...

5) Would putting on Turbocharger give any added fuel economy? Bear in mind this is my daily driver, country roads so it's a constant 90km/h give or take. Yes I know about superchargers and air coolers there's plenty of threads on them. Even the ones about Turbochargers end up going off about the others never really giving a straight answer about the Turbochargers. lol.

I know i added that last one but just curious.

Any help here guys would be appreciated.

 

Look into the 4.1 strokes kit if your rebuilding anyway

 

There's a lot of variables here. Yes a rebuild done by a machine shop should be better than a create motor. But that's if the machinist you take it to is a reputable shop and the level of quality parts you put I to it.
Will it gain power after rebuild yes. Increasing cubes increase power. But don't expect tire roasting power it's not that kind of gains. Look into porting the heads, this will compliment the bigger bore. True power comes from the heads. The better the flow the more power it makes.
As far as parts, quality parts will lengthen the life of your build. But thats also going to raise the cost of the build. You get what you pay for.
You have one of two ways to go with your build. Performance or drivability. In my opinion the stroker kit is a good way to go. I could be wrong but I'm pretty sure you have to tune it after that(more cost). Plus there's the cost of doing the machining and building. So really I guess it all boils down to how much money you want to spend. A "stock" type build should be around $3,000 and if you did the stroker build you probably looking around the $7,000 mark. Oh also look into balancing the rotating assembly.