Beginner question

[dungbeetle]

This is something I should know, but don't. I've got a 4.0 Jeep Grand Cherokee with 130k miles on it. After fixing a few tune problems, the engine runs great. Starts well in cold weather... seems to run well while it's coming up to temp, and runs great when it's heated up to normal temperature .... doesn't stumble when I mash the gas. I've got another engine that is a crate motor with only 300 miles on it. If I go to the trouble to swap it out, will I see a big difference in performance? I mean... I'm sure the more worn engine will have more blow by of the piston rings, and maybe the cam lobes are worn down a little.... maybe the valves don't seal as well, but will that make a hugely noticeable difference?

I've never had a chance to compare something like that.

Richard

 

[greenjeep]

Seems to me a waste to replace a perfectly good motor. 4.0s can easily go over 200,000 with no problem.

 

[mbryson]

you might get a 10% increase or so from swapping motors. If it were mine, I'd wait a while.

 

[kowe69]

you might get a 10% increase or so from swapping motors. If it were mine, I'd wait a while.

Agreed, 10% will hardly be a noticeable increase. I would wait until there is a definite base engine problem with the engine that you are running now before trying to justify installing another engine.

 

[red]

agreed. if it was me i would hold off and wait. if you want more power at a later date you could start building up the spare motor so it has all the power goodies before you eventually swap it in.

 

[grandmaster]

Wait

I would also wait. I own a 95 jeep grand cherokee with 137 thousand miles on it and it runs great. I wouldn't waist your time until something sever goes wrong with the motor in it now. if you want more horsepower do some things to it. (intake, TBspacer, headers, exhaust, high flow cat.) and if you do end up swapping it out, it will all transfer over to your new motor if it is the same.

 

[TooeleBronco]

I would wait also unless you found someone that wants your old motor. You could sell it and have the new one. You would just have to swap it.

 

[RKCRWLR]

I've got another engine that is a crate motor with only 300 miles on it. If I go to the trouble to swap it out, will I see a big difference in performance?
Richard

If your crate is a Hemi you would see a difference - LOL. I would not do the swap. If the motor seems cared for at all, you have a lot of life left in it. I have broke 250,000 miles on 4.0L 3 times with no engine problems, and ran in the 180K range on two others..still going strong. I recently sold a 93 YJ with 100K on it that ran stronger and got better mileage than my 06 Rubi. The 232/258/242 based sixes are very durable motors. I would just hold on to the crate for later.

 

[dungbeetle]

Well, I'm not looking for extra things to do to keep myself busy. If we are only talking about a few per cent improvement, I'd rather spend my time some place more productive. So, I'll go with the advice you've all given me, and just wait for a while at the very least.

Many thanks for the guidance.

Richard in Provo