How do you fix a thrown rod in a 1985 350 engine?

Answer 1

A "thrown rod" is quite rare in a 350, but it does happen. A "thrown rod" is when a rod cap comes off or the rod "big end" disintegrates, leaving the piston unattached. compression and/or combustion pushes the piston down after the failure and the crankshaft repeatedly bangs against the pieces of broken rod. It's a very destructive process. Typically it's caused by heat or excessive wear on the rod bearings, either one will cause metal failure in a rod. A thrown rod is the deal breaker, the one problem says "this engine is finished... So:

# COMPLETELY disassemble the engine # have the crankshaft and remaining rods reconditioned and buy a new rod to replace the damaged one, if the machine shop can't turn the crankshaft you'll need to buy a new one # have the block "align bored" (that's to make sure the block didn't warp, throwing out the crankshaft alignment) # have the cylinders checked for taper and at a minimum, have them "deglazed" # replace all rings and bearings since the crankshaft will now be "undersized" # if the cylinder taper is excessive it will need to be bored requiring that you replace all of the pistons but even if it ISN'T necessary to bore the engine make sure the pistons aren't too worn to put back Since you've gone to all this effort,

# make certain that you have the heads reconditioned # replace the oil pump and timing chain # closely inspect the camshaft and lifters for pits or flat spots and replace the cam and lifters if there is excessive damage # While you're at it, have all of the freeze plugs replaced, it's a lot easier at the machine shop.

Now you have a nice, new engine. Make certain that you follow the manufacturers maintenance schedule. Keep the oil changed at the appropriate schedule, and NEVER EVER let it run low on fluids.