mystery cylinder---

[tim bandy]

I have an early o-320 made in 1957 . No banana plates. I believe the engine was overhauled about 10 years ago. (no logs came with it-) For some reason- it was stored ever since then with no oil at all in it. So when I got it I put in 11 quarts of phillips 66 anticorrosive oil.

I got a borescope about a months ago. want to look at the cam and see how it looks. So I had planned to pull a cylinder to do that. In the mean time- I drained and saved my oil.
I looked into each cylinder through the top plug holes. 3 of the cylinders look bright and shiny and I can see the hone marks near the combustion chamber. All the cylinders are painted grey and have a red/orange square patch on the fins- which I take to be a chromed bore marking. The pistons are stamped "std" on top.
So all that would lead me to believe that the cylinders were bored and chromed.

So when I look at the remaining cylinder --- the walls look different. The walls of this one have a pebbly look- all most like a sandblasted texture---- not shiny like the other 3. I can also see a bit of brown discoloration in patches. Would/could chrome have an odd texture like this ? could it be a different plating process than the other 3 ? The outsides of the cylinders look identical-- as far as the paint and markings.

I am wondering if the brown discoloration could be some rust from the rings -- and its just laying in/on the chrome surface.

If I am taking off a jug- it will be this one -- so I can see it better inside. If there is rust on the cyl. wall
from one of the rings---- what is safe to use to clean away that rust and verify it is not growing on the bore ......

Hot soap and water and a toothbrush followed by a hot blow dry ? any recommended chemicals that would be chrome safe ?

i cant see how/why this cylinder would have a pebbly texture. If it didn't need chroming--- why the red paint--- and if it didn't need chroming it shouldn't have a pebble texture if it had been running right ?

i took pics with the scope -- but I gotta figure out how to transfer them out.

i can see into the valve seats-- the edges of the valves and seats look polished and not ever run. The tops of the pistons still have inked numbers and also show never run.

Any ideas ? (before i pull the cylinder)

Tim

[Gilbert Pierce]

Banana plates are only used on narrow deck O-320-160’s. The -150’s don’t use them. Additionally the cylinder studs are longer to accommodate the the banana plates.

[tim bandy]

thanks Gilbert-----
I didn't know the 150's didn't have the plates. I guess that would be a reason not to try to squeeze any more HP out of it --

[Old3pacer]

how about some pictures from your boroscope?

[tim bandy]

I will try to get pictures posted-----

[Steve Pierce]

So what do you plan to do with this engine with no logs?

[Old3pacer]

Did you do any compression tests?

[tim bandy]

hoping to use it as a bearhawk patrol engine.
Have not tried a compression test as it has never run or been broken in...... not sure what that data would tell me.
And on the stand it is currently
on -- the stand is too close to the ground to put the prop on for a differential compression test----
I am all most finished with a new build table. when that is done I will pull the odd cylinder.

i have to read the instructions with the camera to see how to upload pics. And you KNOW how hard it is for us guys to read instructions. Right up there with going to the emergency room......

I can see with the scope - the bevels on the valves and the seats look polished and shiny new. The valves also have inked numbers on the tops of them. I would think that would tend to indicate new valves (?)