The Stovebolt Site Forums The Shop Area Engine Shop piston removal help

Hello.

Im working from underneath the car. Ive already removed the head on my 216 for valve job.

Issue was low/no compression, so while Im at it figured I would do piston rings as well.

After removing the nuts that hold the bearing on the crankshaft, I pushed the piston up-but it did not come all the way out. It probably has another 1/4 of inch to go before top surfaces. I tried tapping it a little with a hammer and socket extension wrench on both the bottom of the piston head and then the empty hole where the bolt goes to hold the bearing to crankshaft, but didnt want to tap to hard in case I do damage.

Should I just hit/tap the piston out of the chamber forcefully? Is there danger of damaging it? Where should I strike it?

Advice is appreciated.

Thanks,

Judson

It is highly recommended to remove the ridge at the top of the cylinder before removing the pistons.

How does the ridge come out?

use a piston ridge reamer from your flaps.

so its basically just removing that upper lip of rust...its nothing that needs to be reinstalled after the piston is put back in...?

And what about the piston itself...should I just strike it with a mallet and piece of wood? Does it matter where I hit it?

Its more then a ridge of rust. The cyl wears wear the rings contact it. There will be a ridge about1/8 in that the upper ring is down from the top of the piston. You need a ridge reamer to cut the ridge even with the rest of the cyl. After that the piston will come right out with a push from a stick or hammer handle.

If there's enough ridge to prevent the piston from coming out, there is a distinct possibility of enough taper wear in the cylinder to prevent a successful re-ring job. Many auto parts stores will rent you a reamer with a refundable deposit equal to the purchase price of the tool in case you decide not to return it. Once you ream the ridge, measure the cylinder taper by putting a piston ring into the top of the cylinder at the top of the ring travel and measuring the gap with some stacked-up feeler gauge blades. Then push the ring to the bottom of its travel with a piston to keep the ring square with the bore and measure the gap again. Subtract the bottom measurement from the top and divide the result by 3. The result is the cylinder taper in thousandths. If it has more than 5 thousandths of taper, don't try a re-ring- - - -rebore the cylinders and install oversize pistons.
Jerry

Thanks, guys. I ended up getting it out shortly after posting. I used a wooden dowel and it came out with a few taps. The rings actually look ok, but I guess looks can be deceiving, correct? I will go ahead and replace and see if it helps compression.

One question, however. Im just going to order the rings from Napa auto parts, but how do I know if the rings are the right size? It seems they come in different sizes, and I assume mine are stock, but should I measure them or something?

Judson

Stock bore is 3.500"

Use a 3-4 inch micrometer to measure the piston 90 degrees away from the wrist pin and at about the same level. It will measure about 3.497" or a bit more for a standard bore, and .020", .030" or .040" or more larger if the block has been rebored. Most oversize pistons will have the size stamped on the top of the piston once you get the carbon scraped off.
Jerry