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My engine died!!! Piston melted!!!
https://slantsix.org/forum/viewtopic.php?t=41117		 Page 1 of 1
Author:  Polara1974 [ Tue Jul 20, 2010 8:17 pm ]
Post subject:  My engine died!!! Piston melted!!!
Oh well ... the Slant in my car passed away ...

The #5 piston literally is melted!!! here are some pics for you to check
(the ring you can see in #5 piston is the OIL ring)
ImageImageImageImage
and #4
Image

I was driving on the higway in 4th gear at 4000+ RPM, this engine used to climb freely to 5200RPM in 4th. So at 4000 was still climbing with the pedal to the metal, but at 4300 it stoped climbing although I was at full throttle. Then it started to lower th RPM although I keep the gas pedal floored.
I backed the gas pedal and I was able to hold the car at steady 3000rpm for 3 minutes and I stoped at a gas station by the higway. I towed the car home, pulled the head off and found the melted #5 piston, metal chips all over (obviously), and a #4 piston starting to fall apart.

All the time the oil pressure was 60 psi, after stopping every time I turned the key it started but couldn't keep it idling.

So my question is: What happend??!!!!!

Before pullign the head my best guess was broken rings or even a hole/broken piston, but certainly NOT these.

What do you think?

Martin
Author:  hellion_locdogg [ Tue Jul 20, 2010 8:26 pm ]
Post subject: 
Predetination pinging caused by low octane, too high of compression(not your case), too much advance in the timing or bad valve lash to name a few. I would guess bad fuel, betting there are very high levels of ethonal in the fuel down there.

,Cliff
Author:  ceej [ Tue Jul 20, 2010 8:27 pm ]
Post subject: 
Looks like high speed detonation damage to me.

Any mods to this engine? Timing? Fuel?

CJ
Author:  ceej [ Tue Jul 20, 2010 8:28 pm ]
Post subject: 
What plugs also.

CJ
Author:  Joshie225 [ Tue Jul 20, 2010 8:28 pm ]
Post subject: 
Wow, looks like it was running lean. I would check the fuel delivery system and carburetor carefully.
Author:  Polara1974 [ Tue Jul 20, 2010 8:40 pm ]
Post subject: 
The CR was high, although it has dished pistons the head was shaved like 3,5cm, but I don't know exactly how much CR, since I bout the car with this engine configuration alredy assembled. From the picture you will be able to tell that a lot has been shaved form the head deck
ImageImage

I was using Champion N14Y plugs, 96 fuel (don't know about the quality, it's supposed to be Ok ... :roll: ), timing was a bit on the advanced side but without detonation.

Also there was no problem with the pushrod and the rocker on the #5 exhaust valve. The valve lash was set at 0,14 of an inch Int/exh (0,35cm).

Carburator is a Holley 2300 that is the OEM carb for my car. Original mechanical fuel pump with just 200 mile on it!!!
Author:  ceej [ Tue Jul 20, 2010 8:49 pm ]
Post subject: 
Big valves too. Weld-up head? Can't tell by the photo.

With big stroke, at high piston speeds, high speed detonation can occur. That can result in damaging material above the top ring. Looks like what got you. Josh may be onto something as well.
Did you have an A/F ratio gauge on this engine?

CJ
Author:  DadTruck [ Tue Jul 20, 2010 9:06 pm ]
Post subject: 
from a diesel engine reliability perspective
when the issue is melted piston crowns, I have seen engineers chase piston metallurgy and piston lubrication to the ends of the earth, without resolution,, proven causes have always been ignition / injection(diesel) timing. It it was upper bore scuffing I would suspect restricted bore cooling or bore / ring geometry.

Sorry to hear of the failure, but I always liked working with piston failures,, easy to detect, tough to replicate
Author:  Polara1974 [ Tue Jul 20, 2010 9:07 pm ]
Post subject: 
Ceej, yes it has big valves too. The head has been milled, but not welded.

I know about damaging piston above the 1st compression ring, but this thing melted all way donw to the 3rd ring!! That's the one you seen inthe pictures, the oil ring. No A/F gauge.

Luckilly I'll have my new Slant six in short time ...
Author:  walpolla [ Wed Jul 21, 2010 2:02 am ]
Post subject: 
hello,
what -if anything - do you have fitted to the port in #5 intake runner/ brake booster or PCV valve perhaps ?
I have seen a similar failure on an engine here,due to the PCV hose fitted to # 5 runner.
the engine will run very lean and hot on that cylinder because of this. obviously eventually failure occurs.
if the brake booster is fitted there,and has a leak,it will also create the lean (hot) situation.

regards,Rod :D
Author:  Dart270 [ Wed Jul 21, 2010 6:28 am ]
Post subject: 
That sucks. Hard to see that it was not detonation.

Wow, you are the only person I know who has milled a head more than I have. My '64 Dart has a 0.110"/0.210" (manifold/plug sides) angle mill and it did not close the chamber on the intake side that much. My chambers are 33 cc's.

Lou
Author:  Polara1974 [ Wed Jul 21, 2010 7:26 am ]
Post subject: 
Nothin bolted to the #5 intake runner, the brake booster is in #6.
Maybe a bad manifold gasket seal produced a lean condition in #5...
I was able to see oil on the block (driver side) pouring from that intake runner.
Dart270: yep big shaving on the head, also angle milled. Since I haven´t done it myself i can´t tell the chamber cc., I´ll have to measure it, just for the records.
Martin
Author:  MI6 [ Wed Jul 21, 2010 2:02 pm ]
Post subject: 
How much ethanol is in your gas? Here in the U.S. it is typically 10%. If your fuel has much higher percentage the engine will run lean unless the carb is jetted richer to compensate for the higher alcohol content.
Author:  Shaker223 [ Wed Jul 21, 2010 3:21 pm ]
Post subject: 
Seems like the spark plug heat range was on the hot side too.
Author:  AnotherSix [ Thu Jul 22, 2010 12:48 pm ]
Post subject: 
Did the engine eat something?

Were the spark plugs intact? Some of that looks like damage I have seen when the porcelain breaks and gets eaten. I happened to me once and it was from detonation that I had been ignoring.
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