Absolute Noob Engine Questions

Hello! I've been trying to do research but still don't know a lot. Have never rebuilt an engine before but I kind of want to try. If yall recommend against it, maybe ill take it to my mechanic to rebuild it.

here is my dilemma: I've been calling around everywhere to find an engine for my 1989 mighty max, nobody has one, i've looked into possibly rebuilding it as it only spun a bearing but idk if the thing is cracked or not, nor do i kno exactly how to figure that out (do i just need to take the whole engine out and inspect it?).

The bearing spun when i was goin about 70 and i pulled over and it was making a clanking noise. was able to drive it about a mile back home from the mechanic at very low speeds but don't know if it could still be cracked.

I found a 1989 model on facebook marketplace recently but the engine in it has upwards of 230k miles which sounds like a lot (also has a new weber carburetor in it which i want). I was wondering if i could take the parts that i would need to rebuild my engine from that engine as mine has fewer miles and would hopefully last longer, OR! is there a kit i could buy online that would be more beneficial?

I appreciate yalls answers

If you're mechanically inclined, the basic disassembly\re-assembly of the engine shouldn't be a problem. You can find documentation on torque specs, timing settings, etc. online easy enough. If you're going to tackle it just make sure to pay attention to the disassembly process and keep all your parts together, labeled as much as possible. Once you have the engine out and apart, take the block, crank, pistons\rods, and head to your machine shop of choice and have all checked out. Your next step will be based on what the machine shop finds. Good luck!

-3dd13
John 3:17

Pull the rod end bearings out and do a visual inspection. You'll spot the culprit straight away. First thing to determine is how much damage has been done. If the crank journal has been ripped up, it's a done deal and the crank needs to be replaced or welded up and re-machined. Don't be scared of taking it apart - it's already dead and you can't make it worse unless you are using a gas torch to disassemble it. If you are planning on rebuilding an engine, have all of the necessary gasket kits on hand and timing belts/chains, water pump etc. You can do a 'dirty' rebuild by simply running a hone through the piston bores, slap some new stock clearance piston rings and bearings in it and it'll run fine. Have the necessary tools on hand. You are going to need a torque wrench and sets of metric sockets, hex key socket heads (for G63B/4G64 head bolts) and spanners. You can strip it fast with an impact gun and sockets, but don't even think about using it to reassemble the bottom end or head. Take photos, label and store parts including having cardboard 'templates' to indicate what bolts have come from corresponding holes. Use online resources to guide you including the PDF's and manuals available here.

If you've only spun a rod bearing and suffered no other damage, you might be able to get by simply replacing the damaged bearing shell.

Remove spark plugs and drop the oil pan, then turn the engine by hand with a socket on the crank pulley to bring each conrod cap down to an accessible point, see if you can determine which one is loose wiggling by hand. If not, remove one cap at a time to inspect the bearing shells. When you find the damaged bearing shell, feel around that crank journal as well to verify it hasn't been scraped/gouged, should feel perfectly smooth all around.