New OEM Piston chipping

[Mastermind]

Something is going on......but I don't think the piston is causing it. What it is I can't tell just by looking at the pics though.

 

[William Balaska]

Maybe it's pre ignition causing detonation as cranking compression over 200 psi should need race gas. My money is still on debris from the bearing or something else in the rotating assembly.

 

[fordf150]

Something is going on......but I don't think the piston is causing it. What it is I can't tell just by looking at the pics though.

So what is safe compression for these and is it the same at 0 and 5000 foot

 

[Mastermind]

Hell 225 - 240 would be fine on pump gas.

 

[Jon1212]

Hell 225 - 240 would be fine on pump gas.

Good to know.

I had 197psi at 4700' elevation.

 

[William Balaska]

Hell 225 - 240 would be fine on pump gas.

I'm really surprised by that, especially in an engine that can't retard the timing.

 

[blsnelling]

I'm really surprised by that, especially in an engine that can't retard the timing.

???

 

[TermiteBuffet]

Good to know.

I had 197psi at 4700' elevation.

You're much taller than I thought ...[emoji200]

Pedal Tractor Loggin'

 

[mdavlee]

I've run them with 235lbs of compression on 87 octane milling. I doubt compression is causing it. The bore could be out of round and almost cold seizing as it warms up.

 

[Justsaws]

I'll fan the flames for fun, all other things accounted for...

Looks like the piston is sloppy at the top and tight at the bottom, get the piston good and toasty as well as heat sink the cylinder and stuff starts to move. Put a crappy finished piston in the mix and there could be some chipping or flaking, would not take much to abrade the surfaces.

Piston skirt flare, it is either to tight or to loose. To tight can be checked by reusing the same piston to loose cost money.

Looks like there is a lot of extra metal on the cylinder insert intake side, that seems odd.

Pretty good endorsement for the mix though.

 

[Justsaws]

Hell 225 - 240 would be fine on pump gas.

Madness, simply madness, it is this kind of crazy talk that leads to oil threads.

 

[Jon1212]

I'll fan the flames for fun, all other things accounted for...

Looks like the piston is sloppy at the top and tight at the bottom, get the piston good and toasty as well as heat sink the cylinder and stuff starts to move. Put a crappy finished piston in the mix and there could be some chipping or flaking, would not take much to abrade the surfaces.

Piston skirt flare, it is either to tight or to loose. To tight can be checked by reusing the same piston to loose cost money.

Looks like there is a lot of extra metal on the cylinder insert intake side, that seems odd.

Pretty good endorsement for the mix though.

Your combination of astute observations, and humor is welcomed, as well as appreciated.

A good friend of mine remarked to me, "that @Justsaws guy is as sharp as the edge of a Dolmar piston"........LOL!

 

[Jon1212]

You're much taller than I thought ...[emoji200]

Pedal Tractor Loggin'

A midget like yourself probably says that about most people.


@TermiteBuffet You know why midgets always laugh when they run?

 

[Jon1212]

I'm really surprised by that, especially in an engine that can't retard the timing.

So now you're saying my saw is "special"?

That's just dirty pool, Bill, dirty freaking pool.

 

[TermiteBuffet]

A midget like yourself probably says that about most people.


@TermiteBuffet You know why midgets always laugh when they run?

The grass tickles there nutz ? [emoji200]

Pedal Tractor Loggin'

 

[William Balaska]

???

No knock sensor

 

[TermiteBuffet]

After this post ^^^^^^I'm disappointed that no one chimed in with a knock - knock joke.....[emoji200]

Pedal Tractor Loggin'

 

[Justsaws]

Knock knock?

WTF, it's 2am.

Knock, knock?

Go away!

Knock, knock?

Fine, who ever are out there?

What, wait.....knock, knock?

WHO'S THERE?

You should have bought the Echo.

"I have a potty mouth"!

That's not how this works.

 

[William Balaska]

Knock knock, who is it? It's me pre ignition.

 

[rynosawr]

Jon, was this ever resolved??

Was the cylinder out of round or tapered from top to bottom or both?

Did you use emory cloth or scotchbrite on the piston skirt to smooth it back out and try it again?


Did you file down the rough edges where the chips occurred?

I think the chips/flaking caused the scratches you see......

Poor manufacturing tolerances or too much silicon in the mix of the aluminum made it too brittle and then someone didn't deburr it well enough after final machining????



If I refer to my knowledge of pistons, I have much more background in Automotive pistons, and I have even seen some of those cause the same problems because of the same poor manufacturing/ deburring...