the power plant in my 90 Bronco died at the tender age of 330,000km due to a melted piston. the motor is out on a stand stripped down to the block pistons and crank still installed. Now my question to you all; should i rebuild my high mileage block? or just find a lower mileage one to drop in? if rebuild is the better choice how difficult are they to rebuild?
thanks y'all!

 

I'd have the block checked at a machine shop. For all you know, you may just need to have it bored and new bearings installed.

What cause the piston melt?

 

I'd rebuild!

I wonder if #8 piston is the melted one since the old PCV valve is located at the back of the plenum and all the trash gets sucked into the #8 runner. This was changed later around '94 to the center of the plenum due to the high number of blown/melted pistons on the #8 cylinder.

 

buy a short block and rebuild or replace the heads, rebuilt short blocks are aplenty and you can probably find a pretty good deal on one already assembled and it might even have some HP parts in it, check on craigslist and local machine shops..
Rebuilding your own stuff is a pain in the **** and really should be done only when you don't have a better/less expensive/pre-made option..

 

Rebuild! Much better to start with something you know about (condition/use) than with an unknown.

 

330.000 kilometers is about 165.000k miles right?
rebuild what you have unless you're cylinder wall is nicked to hell you're fine if it is get a new block. nothing wrong with your used block.

 

If you want your truck back on the road ASAP for the least amount of money go find a complete low milage replacemernt motor to swap in, any 5.0 truck motor is a direct replacement and a '94+ would give you a power jump. You can then rebuild your original motor or junk it.. just be aware it will cost you every bit of $1500 to rebuild it right and you could possibly score a replacement motor for half that or better.