Is this detonation damage?

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astjp2

Registered User

Utah/Alaska

• May 15, 2021

• #1

This is a small bore continental that has 87 hours since major overhaul. Plugs were wet with oil, consumption was 1 quart every 2-3 hours and compression was 20. Borescope showed a few lines in the cylinder but when I pulled the cylinder it was seriously scored and the cylinder in front of it had the exhaust valve leaking and was orange. At first I thought carbon buildup but now I am thinking detonation damage. What says the tribe? Tim

oh and these were new superior cylinders

 

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Cub Builder

MEMBER

North Central AR

• May 15, 2021

• #2

Detonation damage will leave the top of the piston looking like it was sand blasted clean, then beat with a small ball peen hammer. The last engine I tore down that had serious detonation, the rings still looked good, but the top ring groove was seriously eroded around the top ring on the piston. Your photo looks more like galling, like the engine was assembled with +.010" pistons in a standard bore cylinder. FWIW, that doesn't look like the markings I see on a Superior O-200 piston, which is what I am assuming you have there. Looks more like the Continental piston.

Additionally, unless you hopped it up with high compression and/or loads of advance, it's darned hard to get a small Continental to detonate.

 

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astjp2

Registered User

Utah/Alaska

• May 15, 2021

• #3

They are superior pistons, I cleaned up the other one next to it with ultrasonic and blasted with walnut shells. When I put it together today, I verified piston part numbers, weighed them, checked ring gaps iaw the superior service letter. I may try to see what superior says. The engine was rebuilt by a shop in Oklahoma and has leaked since day one...

 

Steve Pierce

BENEFACTOR

Graham, TX

• May 16, 2021

• #4

Looks like piston slap to me, lots of cold starts maybe. Is the cylinder a new Superior? What did the bore measure and different depths of the cylinder?

 

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astjp2

Registered User

Utah/Alaska

• May 16, 2021

• #5

New superior cylinder. I did not check the bore on this on, the owner wanted me to install other ones so I did those first. I should be able to get some more pictures later today. First priority is put the engine back together. The airplane is kept in a heated hangar. So if it was cold started, I don’t know how probable it was. Tim

 

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dgapilot

FRIEND

• May 16, 2021

• #6

Saw pretty much the same thing on a C85 last year, looks like standard pistons in oversized cylinders.


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tempdoug

PATRON

nd

• May 16, 2021

• #7

looks like someone put connecting rods in wrong to me, so that the squirt holes arent pointing to the opposite cylinder if its a 90 or 0-200.

 

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astjp2

Registered User

Utah/Alaska

• May 16, 2021

• #8

They are superior pistons, I cleaned up the other one next to it with ultrasonic and blasted with walnut shells. When I put it together today, I verified piston part numbers, weighed them, checked ring gaps iaw the superior service letter. I may try to see what superior says. The engine was rebuilt by a shop in Oklahoma and has leaked since day one...

 

8GCBC

Registered User

Oahu

• May 16, 2021

• #9

Looks similar to chrome rings on chromed cylinders. What does the screen show?

 

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astjp2

Registered User

Utah/Alaska

• May 16, 2021

• #10

tempdoug said:

looks like someone put connecting rods in wrong to me, so that the squirt holes arent pointing to the opposite cylinder if its a 90 or 0-200.

Click to expand...

i verify that the squirter is pointed at the piston

 

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astjp2

Registered User

Utah/Alaska

• May 16, 2021

• #11

8GCBC said:

Looks similar to chrome rings on chromed cylinders. What does the screen show?

Click to expand...

it’s a filter, I have not got it cut yet. Now I am fighting pushrods, I have only found 2 lengths and I thought there was 4 part numbers. Exhaust valve is not closed with the rocker installed.

 

windy

SPONSOR

Utah

• May 16, 2021

• #12

Probably the engine was assembled by the little trolls there at Ogden. Nuff said.


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