Piston Skirt Failure

[Oak]

I don't know anything about this seller but a lot of folks on here said they have had good luck with his parts.

https://www.ebay.com/usr/bakt4kids?_...p2047675.l2559

[green407]

Originally Posted by Oak

I don't know anything about this seller but a lot of folks on here said they have had good luck with his parts.

https://www.ebay.com/usr/bakt4kids?_...p2047675.l2559

I've used this seller before. Have had good luck with him, make sure you message him when you order your parts, like piston 0.020 over, and con-rod 0.010 under or he will send you standard sized parts.

[Bob95065]

Update on the engine.

I have a friend that owns a used tool store. He had a Starrett bore mic set that I used to measure the cylinder. It measured standard per the dimensions in the service manual.

I had the block cleaned up by a friend at a machine shop in his parts washer. This revealed pitting in the bore. I bought a 0.030" rebuild kit per the machinist's suggestion and had the cylinder bored and honed.

I started putting the engine back together today and ran into a few hiccups including finding the root cause of the failure.

What happened to this engine is a metal object got trapped between the cylinder and piston causing it to lock up. There was a deep gouge in the piston at the drain hole from the valve box.

When I went to put the valve turners back in I discovered that the intake side had failed. See the pictures below. There are small balls and springs in the turners. These objects came out, went through the drain hole and lodged themselves between the piston and cylinder wall.

So the problems I have now are:

I need to get a replacement valve turner

The crankshaft seals in the kit are the wrong size. Does anyone know the
correct seal numbers? The original seals were National 3120-RB and
49252RBO. These numbers were stamped on the seals. I called NAPA and
they didn't have them and couldn't cross the numbers. If someone knows
these seal numbers and could post them I would appreciate it. I want to
get them locally.

https://photos.app.goo.gl/XrdoEtN3jkUgWbdk8

https://photos.app.goo.gl/VGDPcHSiNnqTL22F6

[Cubcadet_107]

yeah...

that's not supposed to happen

Looks like the piece that's meant to hold everything in broke completely loose from the center! Can't imagine what someone would do to an engine to cause THAT!

[Ambush]

Crappy luck. But sometimes being forced to do the job right works out better in the long run.

A tip for others for measuring bore diameters without inside mic's: Take one of the compression rings and de-bur the ends by pulling folded fine sand paper through them. Use a piston with a clean top and seat the ring square in the bore where you want to measure. With a feeler gauge record the gaps at each measurement. Use the very top, just below the chamfer and above the wear ridge (if there is one) as a base measurement.

Lets say you have a .010" gap as a base on a 3.500" bore diameter.

Just below the ridge is .015"

Halfway down is .018"

And the bottom is .020"

Divide the difference between the base measurement and next measurement by 3.14 and add it to the bore diameter.

So on the bottom measurement the difference is .010"; divided by 3.14 is 3.18 . Rounding that number brings you to a bore that is .003" bigger at the bottom.

You should have a caliper to determine if the bore is oversize already or if the piston is marked.

[ol'George]

Originally Posted by Ambush

Crappy luck. But sometimes being forced to do the job right works out better in the long run.

A tip for others for measuring bore diameters without inside mic's: Take one of the compression rings and de-bur the ends by pulling folded fine sand paper through them. Use a piston with a clean top and seat the ring square in the bore where you want to measure. With a feeler gauge record the gaps at each measurement. Use the very top, just below the chamfer and above the wear ridge (if there is one) as a base measurement.

Lets say you have a .010" gap as a base on a 3.500" bore diameter.

Just below the ridge is .015"

Halfway down is .018"

And the bottom is .020"

Divide the difference between the base measurement and next measurement by 3.14 and add it to the bore diameter.

So on the bottom measurement the difference is .010"; divided by 3.14 is 3.18 . Rounding that number brings you to a bore that is .003" bigger at the bottom.

You should have a caliper to determine if the bore is oversize already or if the piston is marked.

I always make it a practice to
check ring end gap!!
I got bit in the Ass back in '54 with a supposedly std. set of rings I installed in a worn bore, in a stove bolt chevy 6.
One set of rings had a .010 oversize top ring and when started, it ran for a few minutes then seized, bending a con rod.
That cost me a replacement junk yard engine.
Once burned, twice shy.
I was young and inexperienced.

[finsruskw]

The rotators probably got wrecked from improper use of the valve spring compressor.

Instead of getting UNDER the rotator base with the fork end whoever did the work, STABBED it, stressing the assembly to the point of failure.

[Bob95065]

Originally Posted by finsruskw

The rotators probably got wrecked from improper use of the valve spring compressor.

Instead of getting UNDER the rotator base with the fork end whoever did the work, STABBED it, stressing the assembly to the point of failure.

Maybe and if it did that error caused a major failure when the engine locked up.

[Bob95065]

I got the engine back together and running. I got the correct seals and a couple solid valve bases. I have a few issues.

The ACR on thecam stopped working. it started fine the first few times then the starter struggled on the compression stroke. If I rolled the enginevpast compression it would turn over with the starter. I feel like I should look for a cam with a working ACR if I pull the head and see that the exhaust valve isn't moving when it should to releave compression.

The PTO clutch wasn't disengaging at first but released after using it a few times.

I have an oil leak that I'll address while figuring out the ACR issues.

It's good to be closer to getting this done. The grass is getting long and needs to be mowed.

[ol'George]

It might be easier to just look in the valve box to see if the Exhaust valve is lifted a bit on the compression stroke but closes completely at about TDC.
Also, you get to check your Ex lash just incase it changed affecting the ARC,
and you can save a head gasket replacement.
Well anyway, that is the way I would go about it.