Melted Piston

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Jun 6, 2001 | 11:19 PM

bigred78

Thread Starter

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Joined: Jun 2000

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From: Fridley, Minnesota

Melted Piston

A chunck of my piston broke off in my freshly rebuilt 460 and melted in the cylinder. I have a CR of 9:1. The timing if set at 10 degrees and run 92 octane. They are TRW forged pistons with moly rings. Is this a defect in the piston or is the engine tuned wrong. I managed to scrape the melted chunks off the cylinder wall and honed it a litte. There is just a few not to deep scratches. Does anyone know how this happened so it don't do it again. Any help will be appreciated.

Bob

Jun 7, 2001 | 05:49 AM

cobrajet

Tuned

Joined: Feb 2000

Posts: 309

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From: michigan

Melted Piston

let me take a guess,, did the piece come from the area from the top of the piston and the first ring groove on the side??

Jun 7, 2001 | 03:48 PM

bigsnag

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From: Pryor

Melted Piston

Bigred,
Were you experiencing any (and I mean any) spark-knock? Were you pistons flat-tops or did they have a dome?

Jun 7, 2001 | 05:20 PM

bigred78

Thread Starter

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Joined: Jun 2000

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From: Fridley, Minnesota

Melted Piston

Yes, the chuck came from the top of the piston, where one of the dishes are. They are flat top piston and have dishes. There was some sort of tapping sound coming from the engine, but not too bad before it happened.

Bob

Jun 7, 2001 | 05:22 PM

bigsnag

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From: Pryor

Melted Piston

Red,
How long was that tapping going on?

Jun 7, 2001 | 06:47 PM

bigred78

Thread Starter

Junior User

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From: Fridley, Minnesota

Melted Piston

It did it all the time. I thought it was just the rocker arms were adjusted to loose. There is about 2000 miles on the engine.

Jun 8, 2001 | 09:56 AM

TBirdGuy

Mountain Pass

Joined: Apr 2000

Posts: 241

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From: Holland, Michigan

Melted Piston

Don't know about anyone else, but that sounds like spark knock to me. Sounds like your timing was to advanced, or your vaccum advance is to...well, advanced. Only other thing to ask is, is your vaccum advance hooked up to the right vaccum port on your carburetor? If it's not, then you're giving vaccum to the advance all the time, possibly causing spark knock and a burnt piston.

TBirdGuy

"Stuck with a m*par, Settle for a ch*vy, Happy with a Ford!!!!"