Lost Compression in cyl 7&8 Mystery Solved!

[Crackerjack17]

So it looks like a cherry picker and you can pull the engine out from top . I thought you only could drop it out from bottom with car o. Lift . Good work

Yep. Pulled it out the top and didn't have to discharge a/c. Is it the easy way hell no. It would be easier to take front end apart and walk the whole engine tranny out the front. Did it all myself with a quickjack lift and cheap cherry picker.

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[Crackerjack17]

Great choice on the setup. Who built the shortblock?

It's an MMR 1200 shortblock. Which is manley billet I beams, manley forged pistons with chromoly pins, arp heads studs, arp crank studs, arp side bolts. Boss 302 balanced crank. I also have about everything else they make for the front and back of engine. Yes, I should have just ordered it sleeved, but costs kept climbing and I don't have plans to go over 800-1000 hp. I wanted something reliable that I can beat on. This is a 98% street car.

 

[DavidHuff]

Thanks for posting all this great information and Good Luck!

 

[yote41]

makes me worry alittle. what do you think caused it? any long highway pulls?

 

[Jay-rod427]

makes me worry alittle. what do you think caused it? any long highway pulls?

He said he regularly did 160 mph. so ya that'll do it. long boosted pulls is dancing with the devil on stock pistons, even at moderate power levels.

 

[yote41]

ah ok makes sense

 

[z06psi]

It's an MMR 1200 shortblock. Which is manley billet I beams, manley forged pistons with chromoly pins, arp heads studs, arp crank studs, arp side bolts. Boss 302 balanced crank. I also have about everything else they make for the front and back of engine. Yes, I should have just ordered it sleeved, but costs kept climbing and I don't have plans to go over 800-1000 hp. I wanted something reliable that I can beat on. This is a 98% street car.

Very nice. What did that set you back if you don't mind. I am going that route once I am back on the mainland.

 

[gimmie11s]

Great thread, great info, good details on all of it. This is very useful.

Looks like rings butted and broke the lands.

I wonder if e85 would have prevented this due to e85's inherent ability to burn cooler than gasoline.

 

[SVT-DADDY]

All this talk of blown motors makes me eat too much......and drink too.

 

[ProChargerTECH]

Who was the tuner BTW?

No tuner could have saved that motor.

Typical tight ring gap + highway pull = heat failure.




The only thing getting old about seeing these failurs, is all the tuners throwing other tuners under the buss. (and the FB group guru's chiming in)

Nothing in the ECU says "Save piston from .009 ring gap" :lol:

:cheers:

 

[pro 5.0]

IMO seeing that the top ring sees the most heat it would be the first one to butt, and when that happens it usually blows the top of the piston up near the fly cut area on the intake side. I would lean towards detonation to be the cause of the rings breaking like that it would be interesting to measure the width of the rod bearings on those 2 cylinders compared to the rest to see if they squished out from being pounded on, also could check the wrist pins for any tweaks that would indicate there was detonation. However with every failure and upgrade lurks in the shadows and you've got a solid replacement there with those pistons and I beam rods, it will come back stronger than ever. Good luck with the build and double check fueling and tune before going nuts on the new motor.

 

[ProChargerTECH]

NICE!!!!! :cheers::cheers::ford:

 

[ProChargerTECH]

IMO seeing that the top ring sees the most heat it would be the first one to butt, and when that happens it usually blows the top of the piston up near the fly cut area on the intake side. I would lean towards detonation to be the cause of the rings breaking like that it would be interesting to measure the width of the rod bearings on those 2 cylinders compared to the rest to see if they squished out from being pounded on, also could check the wrist pins for any tweaks that would indicate there was detonation. However with every failure and upgrade lurks in the shadows and you've got a solid replacement there with those pistons and I beam rods, it will come back stronger than ever. Good luck with the build and double check fueling and tune before going nuts on the new motor.

I have actually done destruction testing on these motors.


1) If you force detonate them... you break the top of the piston.

2) Heat from long duration pulls (and low timing, due to high boost) kills the middle ring lands (like this image)

3) Not enough or too much fuel = melted stuff.



Trust me, I have broke things in the name of science.

 

[pro 5.0]

No tuner could have saved that motor.

Typical tight ring gap + highway pull = heat failure.




The only thing getting old about seeing these failurs, is all the tuners throwing other tuners under the buss. (and the FB group guru's chiming in)

Nothing in the ECU says "Save piston from .009 ring gap" :lol:

:cheers:

Wow had no idea the top ring gap would be as tight as .009 figured it would be at .014 - .016, E85 might have had more cushion as with 93 you can't always control what's coming out of the ground.

 

[ProChargerTECH]

Wow had no idea the top ring gap would be as tight as .009 figured it would be at .014 - .016, E85 might have had more cushion as with 93 you can't always control what's coming out of the ground.

In the motors I have taken apart they seem to average around 12-15

But I have had some as right as 9 (and they were the broken ones)

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