High mileage engine - when to replace or rebuild?

I've got 307k on my 95.5 3.4 engine now and it's getting to the point where it needs some loving. Oil pan leaks, injectors need cleaned I suspect, has exhaust manifold leaks, dropped a spark plug electrode in one cylinder, and has 110-145psi compression in the cylinders. Otherwise it still runs fine minus not starting well when hot and lagging badly when it's cold while accelerating.

I replaced the timing belt and all components at 295k.

Wondering at what point I should maybe look for a lower mileage junkyard motor, or just fix these issues as they come up? I'm kind of weary to have it rebuilt as it seems like the tolerances are never kept as good as they are from the factory. Just worried I'll fix all these things and it will throw a rod bearing or something. Plus the low compression...

 

I'm about to roll over 354K on the original 3.4 in my 2003 DC. I keep up with regular maintenance...change oil every 3,000, timing belt every 100,000, fix small items as them come up, etc. If you're not abusing it there should be plenty of life left in your engine.

 

They dont break at a convenient time... if you have the tools, the time and a local dealer or decent auto parts store you can put a JDM or ? motor in over a weekend for around $2k.

 

Just care for it until it shits the bed, then, LS time baby

 

You didn't run it with that electrode in the cylinder, did you???

 

Thanks for the advice! I'll keep running it until it really goes kaput.

Ha. No, I shut it down pretty quick. Sounded like marbles running through the motor all of a sudden. Pulled the plug, and attached a magnet to a borescope and pulled the pieces out. Didn't appear to chip a valve or anything. Definitely didn't do the piston any favors but the cylinder walls looked ok. Time will tell I suppose. But I've put 10k on it since then.

 

These motors are usually pretty good up to about 500,000, but it seems like there are a lot of blown
head gaskets around that number including mine.

Take your time looking for a engine in a truck running if it comes to that.

Oil leaks start showing up at from age and miles.


Mine popped at 480,000

 

@OP: I had to replace my clutch & carrier bearing when my clutch went out in Oct. 2018. I also had my mechanic service both front & rear differentials. Then my headgaskets on my engine blew up after 275,000 miles in December. My mechanic advised me to get a used low mileage engine block for an engine swap instead of rebuilding the original engine block. He found a used 3.4L V6 engine with 130,000 miles for me for $1200. 2 weeks later, I got my truck back with the engine swap running in perfect condition. It was an expensive repair, but I'm keeping the truck for another 10-15 years.

 

It is a personal choice .

What ever works best in your case.

another option by a used engine rebuild as time and budget allows .

When the engine in the truck fails swap it in.

In most cases it never works like this something will happen at the worst time.