Why do #5 and #7 pistons have chunks missing?

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Oct 2, 2008 | 06:48 AM

#21

ajg1915

Race Director

Joined: May 2005

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From: West Norriton PA

St. Jude Donor '08

Quote:

Originally Posted by waddisme

I haven't found any of my missing pieces. Don't know where they have gone. BTW, I heard no knocking or pinging or I would have stopped dead in my tracks.

I wonder what the underside of the head looks like on those cylinders ?

Are they all dinged up from the metal debris being bounced around ?

Probably ended up getting blown out the exhaust ports.

Well if you didn't hear a lot of pinging or power loss then maybe detonation was not your causation of this failure.

Oct 2, 2008 | 08:53 AM

#22

waddisme

Thread Starter

Safety Car

Joined: May 2007

Posts: 4,812

Likes: 46

From: Taylorsville North Carolina

The heads looked fine. I agree with you, it probably all went out the exhaust, because there was a lot of stuff coming out the tailpipes

. Here is a pic of the heads:

[IMG]

[/IMG]

Oct 2, 2008 | 10:41 AM

#23

ajg1915

Race Director

Joined: May 2005

Posts: 15,960

Likes: 21

From: West Norriton PA

St. Jude Donor '08

You were a lucky guy, I've seen some pictures of where the face of the head looked like someone beat it with a ball pean hammer.

Quote:

Originally Posted by waddisme

The heads looked fine. I agree with you, it probably all went out the exhaust, because there was a lot of stuff coming out the tailpipes

. Here is a pic of the heads:

[IMG]

[/IMG]

Oct 6, 2008 | 12:51 AM

#24

Bill Curlee

Tech Contributor

Joined: Dec 1999

Posts: 32,910

Likes: 2,402

From: Anthony TX

CI 6,7,8,9,11 Vet

St. Jude Donor '08

WOW. Good info and a very inforative thread.

BC

Oct 7, 2008 | 11:10 AM

#25

waddisme

Thread Starter

Safety Car

Joined: May 2007

Posts: 4,812

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From: Taylorsville North Carolina

Tough way to learn about pre-ignition. Hopefully, it will not be an issue with new na motor. Not even sure meth is a safe protection for that when doing 25 min track sessions. As much fun as a sc is, it is tough to make it work for road racing. I will miss it though.

Oct 7, 2008 | 11:14 AM

#26

kornfreak_401

Melting Slicks

Joined: Mar 2007

Posts: 2,123

Likes: 5

From: DFW/BCS Texas

i almost want to say its because they leaned out.

Oct 7, 2008 | 06:15 PM

#27

K RIPPER

Burning Brakes

Joined: May 2008

Posts: 1,147

Likes: 1

From: Mohegan Lake New York

AGJ1915 gave a pretty accurate description I would like to expand on that just a little detonation in its worst form, the spark plug ignites the air fuel mixture as the flame front travels across the top of the piston it compresses tha remaining A/F mixture to a point that it ignites (explodes)so instead of the mixture burning and as it burns across the piston top and pushes it down the two fronts meet usually when the piston is on itsa way up and that pressure is going some where usually the weakest spot . my guess as far as the broken piston is concerned you could have experienced ring flutter when detonation is encountered the ring flutteres( rattles up and down) and this breaks the ring which then proceedes to break the piston.My advice set the air fuel mixture where its right then richen it up just a tad set the timing then back it up just a little. You never hear the detonation that breaks your motor the detonation usually occurs when the motor is screaming and you can't hear it look at the rod bearings they will tell you how severe the detonation was cause the detonation tries to push the piston down when its going up

Oct 8, 2008 | 02:07 PM

#28

2ndVette

Drifting

Joined: Jul 2000

Posts: 1,289

Likes: 1

From: the West is the best

ahh Lucky#7 !!! . This piston damage is, unfortunately, common with the LSx blocks. The #5 and #7 cylinders tend to run lean and damage to the ringlands occurs.