How To Remove Pistons From An Engine

How To Remove Pistons From An Engine

Since Michigan has a stay-at-home order due to the coronavirus I’ve been partaking in what I am now officially dubbing Wrenchfest 2020—an all-out repair assault on my various broken cars. Last weekend was a good one for my Jeep Cherokee Golden Eagle, as I cracked into its AMC 360 V8 engine. Here’s a look at how I removed those eight pistons.

Days have their ups and downs given the current global environment, but I have to admit this past weekend was a good one for me. I occupied my mind with a project, namely tearing into the AMC 360 sitting in my garage.

My 1979 Jeep Cherokee Golden Eagle, I have to admit, ran just fine when I bought it. It had a broken exhaust bolt in the cylinder head, so I took the head off and had a shop remove the bolt. By the time I got to reinstalling the head many months had passed and my cylinders were all rusty. It was surface rust, but rust nonetheless, so I decided to yank the motor and hone the bores. This was, retrospectively, a foolish move. A bit of surface rust should have been fine.

Fast forward a few months and I’m now elbow-deep inside a V8 motor, so let’s look closely at the contraption since it’s just right there, shall we? First, here’s a peek at the many projects that I’m sure will take up the entirety of this stay-at-home order. If they don’t, we’re all doomed:

After disconnecting the Golden Eagle’s motor from the transmission and the engine mounts, and unhooking all the throttle linkages, wires, accessories, and other ancillary bits, I used a crane to pull the engine out of my Jeep. I then bolted the mighty iron block to an engine stand.

In the image above, you’ll notice coolant dribbling out of the engine block where normally the cylinder head would sit. You can see five of the cylinder head bolts in the photo; those were there fastening this cylinder head to the deck:

With both heads and exhaust manifolds off, I removed the lifters that sat under the absurdly heavy intake manifold, which I also removed (see below). The hydraulic lifters ride along the camshaft. As a camshaft spins, one of its lobes pushes a lifter, which presses against a pushrod, which lifts a rocker arm in the cylinder head, opening an intake or exhaust valve. The lifter ensures that the lash in the valvetrain is pretty much nonexistent; I recently wrote a story all about how hydraulic lifters work, so check that out.

I removed the lifters with a magnetic tool. Leaving the lifters in the motor is a mistake I’ve made before; when I went to flip the motor over to see the bottom end, the lifters fell out. That’s a big deal, since individual lifters have to remain mated to their particular camshaft lobe, since the two wear together in a very specific manner.

For this reason, once I’d removed all of my lifters, I laid them out on a piece of cardboard and labelled them to keep track of which lifter matches up with which cam lobe:

Here’s a look at the cams through the same holes that the lifters once sat in:

You probably noticed that with the cylinder heads removed you can see the tops of the pistons. To get those pistons out you’ll have to get to the bottom end of the motor and disconnect each piston’s connecting rod from the crankshaft. Before doing that, you may have to do what’s called “ridge reaming.” This is just shaving off the ridge that exists at the junction between where the piston rings were riding along the bore and the part of the bore that has never seen any wear from piston-ring friction.

You’re essentially just shaving a bump down so that the piston rings won’t get caught as you try to push the pistons out of the cylinder.

The tool you’ll need to do this is called a ridge reamer; I rented mine for free from O’Reilly Auto Parts. It’s actually an incredibly simple tool. Basically, you spin the motor over by hand (grab the crankshaft pulley and give it a twist) to get a piston down towards bottom dead centre. Once you’ve gotten it down far enough, you’ll insert the ridge reamer on top of the piston such that the blade sits just below the ridge, but only once you’ve turned the main cutting head counter clockwise to thread it far down towards the tool’s base.

Then you crank down the expansion bolt to get the reamer to grab the inside of the cylinder wall (this isn’t likely to damage it, considering how soft the tool’s three feet are). From there, you move the cutting head towards the cylinder wall with the cam screw in the “two” position. Then you lock the cutting head into place, turn the blade cam to the “three” or “cut” position, and start cranking the main cutting head screw clockwise.

Using some cutting oil along the way, you’ll find yourself cutting the untouched wall of your cylinder:

In this image, you can see metal shavings around the cylinder wall as I cut the ridge. If you put a rag under the reaming tool you can make sure these shavings don’t get caught between your piston and the cylinder wall. It’s also a good idea to clean any shavings that remain after this operation and, if you want, slap a bit of light oil on the walls. You want that piston to just glide right out of that bore.

(You’ll notice that to the left of the cylinder I’m working on, there’s another cylinder with a black ~1/4" tall ring at the top of the bore; that’s the ridge that needs to be cut off).

Once I had eight ridges reamed, I flipped the motor over, exposing the crankshaft (I’d already removed the many screws holding on the oil pan—see below):

Then I unscrewed the oil pump using a pipe wrench and simply used a half-inch socket and ratchet to zip off all the connecting rod cap screws. Here’s a look at the bottom end of the motor:

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Motor ain't gonna fix itself.

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And here’s a look at the ridge reaming operation, followed by the removal of a piston. A few things to note, here: Once I took one of the connecting rod caps off and set it aside, I then put a piece of rubber hose over the connecting rod studs (I point it out in a picture below).

This allowed me to push the piston using a wooden hammer handle from the back side without worrying about the stud scratching the crankshaft. Here’s what I mean:

It’s a smart idea to label each piston/rod assembly and end cap. These end caps are mated pairs to their specific connecting rod. In some vehicles, the connecting rod is actually forged as a single piece and then fractured to create the end cap. This creates an extremely precise fit between parts, but as you might imagine, a cap that has fractured from one rod isn’t likely to fit onto another rod very well.

So keep those caps-piston assemblies paired together and make sure you know which cylinder each goes to. Sometimes, there are markings on the parts to help you keep things straight. Right now, I’ve got my piston/rod assemblies sitting on my brother’s Ford Mustang (see above), lined up in order from front to back (yes, on V-engines, the cylinders in one bank are not exactly across from those of the other bank). I’ve also labelled the connecting rods with a number and an arrow:

As you can see, the crankshaft is still in the block:

To remove that, I’ve got to take out all of those main bearing cab hex bolts you see in the picture above but first, I have to disconnect the crankshaft from the camshaft—that means, taking off the timing chain.

The photo above and video below provide a look at that timing chain which I’m going to remove as soon as I have a puller to snag the camshaft sprocket from the cam:

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Eight AMC 360 pistons sit atop a 1966 Ford Mustang.

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It’s all work-in-progress. While it’s silly that I’m even tearing into this engine considering how well it ran before, I’m still having fun and occupying myself during a trying time in world history.

Once I get the crankshaft out, I’ll take a few measurements to make sure the bores are within spec and then I’ll grab a drill and a ball hone to clean up the cylinder walls before slapping everything together with new piston rings and crank/rod bearings.

My goal is to get the ‘79 Cherokee running by June. The Eagle deserves to fly in the sunny weather.