How do you replace piston rings in a Chevy 350 engine?

Answer 1

It's a MAJOR engine rebuild. If you haven't done one before you really need to work with someone who can give you pointers.

My assumption will be that the engine has a lot of miles on it and it's pretty much worn out. Some people will just try to throw in a set of rings in hopes of making it run better but that never works.

But if you insist...

Disconnect the battery.

Remove the heads. That will mean taking off much of the peripheral stuff like the alternator, AC compressor and other pieces like the intake and disconnecting the exhaust manifolds.

Once the heads are off, check the top of the cylinders. You'll need to remove any built up deposits to get down to the metal. If there is a ridge around the top where the old rings wore down the cylinder wall it's an indication that there is "cylinder taper", meaning that the new rings will not seat or will cause excessive movement in the piston grooves. If that's the case, remove the engine completely, continue disassembling it and take it to a competent automotive machine shop to have the cylinders bored.

If you DON'T see a ring groove, remove the pan, mark the rods and caps, remove the caps, push the pistons through the top of the cylinder, buy, rent or borrow a cylinder hone and hone the cylinder walls until you see even "cross-hatch" marks on all cylinder walls, then replace the piston rings being careful to first clean the old ring groves of all deposits. Once the rings are in the proper groves (consult the ring packages to make sure you're putting the right rings in each grove) make sure the rings are turned so that no two ring gaps are adjacent to each other. Then (again, rent, borrow or buy a ring compressor)push the piston and rod back into the original cylinder, making sure that the piston is aligned the same way it was when you took it out, ie, the mark on top of the piston has to be to the front of the engine.

It's best to replace the rod and main bearings at this time, but that's a different story. You should use a micrometer on each rod bearing "journal" to make sure the crankshaft hasn't worn "out of round". If you haven't done this before, it might be good to consult with someone who is experienced. If the crankshaft is worn it MUST be turned, again, by a qualified machine shop. Replace the bearings, using proper oversized bearings if necessary. The bearing surfaces must be SPOTLESSLY clean before assembly then use assembly lube on the bearing surfaces before bolting the rods back on the crankshaft. Use a calibrated torque wrench to tighten the bearing caps to the specified torque. You'll need to consult a book for torque specs. Check with your library, they usually have a Chiltons or Haynes manual.

It's usually a good idea to replace the oil pump when you have the engine open, but that's up to you.

Inspect the heads for excessive valve wear; worn valves will sit deeper in the seats. Again, you should take the heads to your local machine shop to have them properly inspected for warping, cracks and valve and guide wear.

Using new gaskets, replace the heads and oil pan, making sure that all surfaces are clean and undamaged before assembly. Follow all tightening sequence recommendations and make sure you torque everything properly.

While the intake manifold is off, inspect the EGR valve assembly and clean the passages. Replace the valve if necessary.

Reassemble the rest of the engine the same way you took it apart, taking special care with the intake manifold to avoid coolant, oil and vacuum leaks.

The Chevrolet 350 is one of the better engines ever built and if properly assembled and maintained it should easily last two-hundred-thousand miles.