Ring Failure w/pics

[jhanson1750]

Well I was going to just remove all the accessories and freshen up the look of the engine bay but after a visual inspection I found some oil leaks that I wanted to address. We got the engine out yesterday and this is what I found. Broken ring and the ring land was cracked. Glad I have an RJC girdle on as even with it the mains have walked a little as evidence by the fretting on the mating face of the main cap. Other wise things look good for a motor that has taken a LOT of abuse! Just a note, I have bee 30lbs with race gas and alky and very little timing before I learned the other way to get power, less boost and more timing... I called Weisco and will have a replacement piston and new rings here tomorrow to get her back together. So new bearings, rings, gaskets and fresh oil pump rebuild. View attachment 194168

 

[jhanson1750]

Ring land

 

[Buick Mark]

 

[jhanson1750]

Just another couple of things I would like to pass along.
1, Painting the valley looks cool and may help oil return but NOT if you don't prep PERFECTLY! I had several spots @ 2-4" diameter that the paint had flaked off and was in the oil pump pickup screen
2, De-burring the block is time well spent! I spent almost a week after work every day with die grinders and cartridge rolls getting flash and sharp edeges out/off of the block and heads. After seeing the main caps have walked I have no doubt the girdle saved the bottom end but the stresses we put into these tiny block I would think cracks would start from any sharp edge left near the main webbing.

I used to get mad when I failed a part but now I just see where either I got it wrong or I exceeded a design limit.
I will post pics as she goes back together. Jon
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[slamming 6]

Check the girdle and make sure the clearance is right i have seen alot of girdles installed wrong,the caps all walked like yours.I would like to see a picture of the cylinders.is the broken ring on the piston that broke the land.

 

[jhanson1750]

Yes, same bore. #6. I checked it with bore gauge and 3.8234ish. I was using a half thou indicator and its just shy of the 5 thenths. I'm going to hone it and that will take a couple tenths. So it will be a little loose but I can live with it. I will get some pics of the bore posted tomorrow. The girdle was set up at the machine shop and I remember it being good on one side and 0.0015 tighter on the other so I worked the pan rail with a honing stone to get it the same on both. I will have to get out my build book for this motor to see what the clearance was on the pan rails with the girdle/mains torqued.
Also, the oil ring set is crushed 180 out from the second ring in the above pics. The wrist pins all still move correctly (full floaters).
Any questions/sugestions are welcome. Jon

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[Nick Micale]

....... After seeing the main caps have walked I have no doubt the girdle saved the bottom end but the stresses we put into these tiny block I would think cracks would start from any sharp edge left near the main webbing....... Jon.......

I have a different opinion about the girdle "saved the bottom end" as we have seen many blocks trashed with a crack in the webbing between the main bearing saddle and the cam bearing with a girdle, and the most recent was 6 months ago?

Your bearing wear is what we see when a stock, cast crank is run hard, and the crank flex will leave a wear pattern like that. Before the turbo cars, we experienced even worse bearing wear like this in the Buick 455 V-8 as that crank is longer, and would give up usually at the 500 HP level.

If the customer does want a girdle, almost always steel caps are also installed, and our caps do not walk.

When the "affordable" V-6 forged crank became available, we then eliminated this flexing issue and had a much more durable bottom end and we added 2 steel center caps to the 109 block, as well as the 4.1 blocks.

To me, re-using your stock crank in this build at this level is like walking around with a grenade in your pocket with the pin pulled half way out!

 

[jhanson1750]

To me, re-using your stock crank in this build at this level is like walking around with a grenade in your pocket with the pin pulled half way out!

HAHAHAHA!!!!!!! I plan on a build with a steel crank but not in the cards right now. I looked for 8 or 9 months for a good steel crank when I built this motor in 2007 and there were just none to be had without going "cut just for me" pricing!
I kinda discounted the steel caps when I put it together as I didn't think I would be running low 11s. My plan was to go 11.50s as best but it just evolved into running low 11s and held up very well. I probabily have 400 passes or more on this setup.
Oh and this motor has had 7 sets of headgaskets on it in the time I have been running it and this is the first time the motors come back out.
I just want to get her back up and running so I can start getting the parts together for a stroker/real head build. I really have been impressed with what this motor has provided given the iron heads, stock crank.

 

[Chuck Leeper]

What do the ends of the unbroken rings look like?

 

[BEATAV8]

Why do you think the rings cracked?

Quite a bit of carbon or burned oil in the ring land area, but that's to be expected sorta "after the fact" with the broken rings I suppose.

 

[Nick Micale]

Why do you think the rings cracked?..........

If you see the OP has replaced head gaskets 7 times on this build, it becomes obvious is has been subject to more than its share of detonation, and finally some pre-ignition to finish off the rods and pistons!

Hard to say which came first that the piston ring land broke or the ring, but my guess is the piston went first?

No real signs of detonation on the piston, but pre-ignition hits like a sledge hammer on the compression stroke and it only takes a fraction of a second for serious damage to occur.

Hopefully the tune will be "adjusted" and worked on to provide more reliable service.

 

[RmvBfrFlght]

I have a different opinion about the girdle "saved the bottom end" as we have seen many blocks trashed with a crack in the webbing between the main bearing saddle and the cam bearing with a girdle, and the most recent was 6 months ago?

Your bearing wear is what we see when a stock, cast crank is run hard, and the crank flex will leave a wear pattern like that. Before the turbo cars, we experienced even worse bearing wear like this in the Buick 455 V-8 as that crank is longer, and would give up usually at the 500 HP level.

If the customer does want a girdle, almost always steel caps are also installed, and our caps do not walk.

When the "affordable" V-6 forged crank became available, we then eliminated this flexing issue and had a much more durable bottom end and we added 2 steel center caps to the 109 block, as well as the 4.1 blocks.

To me, re-using your stock crank in this build at this level is like walking around with a grenade in your pocket with the pin pulled half way out!

Nick, I agree with the result difference between the cast iron and steel cranks. However, I disagree with the reason. A steel crank at 200* F is twice as flexible as a cast iron crank at 200*F:

http://www.engineeringtoolbox.com/young-modulus-d_773.html

The issue is the block is flexing and the cast iron crank is not, while the steel crank flexes with the block. This also shows up in the bearing wear pattern.

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[Nick Micale]

.. I agree with the result difference between the cast iron and steel cranks. However, I disagree with the reason. A steel crank at 200* F is twice as flexible as a cast iron crank at 200*F:............

It has been many years since I received my engineering degree, and have not opened one of those books since then, and defer to common sense and actual real-world results!

One thing we do know is a forged crank WILL take more HP than a cast crank, and after a hundred or so forged crank builds, we do not see these issues or others like we do with cast cranks, so to me, the "young-modulus" is really a moot point?

There are other factors to consider such as the block integrity, as flex in a cast iron piece would not be tolerated very long as fatigue would certainly take its toll.

I am fine with you not agreeing on my comment, but I do know if a forged crank that weighs almost twice as much as a cast crank, and have never broken one, and does not eat bearings like a cast crank, they have been very much MORE reliable than a cast crank, that is what I want in my performance engine.

 

[RmvBfrFlght]

I am fine with you not agreeing on my comment, but I do know if a forged crank that weighs almost twice as much as a cast crank, and have never broken one, and does not eat bearings like a cast crank, they have been very much MORE reliable than a cast crank, that is what I want in my performance engine.

No doubt about it, one day I'll build the 4.1 I'm sitting on. And it will have a forged crank.

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[Chuck Leeper]

"If you see the OP has replaced head gaskets 7 times on this build, it becomes obvious is has been subject to more than its share of detonation, and finally some pre-ignition to finish off the rods and pistons!"

Must be the "7 yr itch"... As in itchin' for an engine that's not a hand grenade.

 

[BEATAV8]

Nick, I agree with the result difference between the cast iron and steel cranks. However, I disagree with the reason. A steel crank at 200* F is twice as flexible as a cast iron crank at 200*F:

http://www.engineeringtoolbox.com/young-modulus-d_773.html

The issue is the block is flexing and the cast iron crank is not, while the steel crank flexes with the block. This also shows up in the bearing wear pattern.

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I think you have that backwards. Higher modulus of elasticity means higher stiffnes. Opposite of flexibility.

 

[bison]

Cap walk looks typical of a 600+hp engine with a stock crank. Polish on bearings in #2 and #3 indicates crank flex.

 

[mgmshar]

I think you have that backwards. Higher modulus of elasticity means higher stiffnes. Opposite of flexibility.

This is correct. The higher the modulus of elasticity, the lower the deflection for a given load. So, the steel crank is actually about twice as stiff (deflects half as much) as the cast iron crank.

I read a lot of automotive trade magazines for my job. I'm reading more and more about the OEM's using steel cranks in the higher specific output engines (turbocharged GDI stuff). They are doing it so the cranks will deflect less (higher stiffness) and be less likely to break (higher strength) than a cast iron equivalent. If I were building a new LC2 from scratch and money was no object, I'd use a steel crank to keep deflection down. If you are going to spend the money for a stiff girdled block, a stiff crank should go with it.

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[jhanson1750]

Just so everyone knows. Has it had some detonation, yep. Early on with it when I was figuring out what my car liked. There is no damage to any of the piston crowns just the ring land failures on #6. No rod issues, but that's why I went with "H" beam eagles with ARP2000 hardware. More pics to come. After looking at the both rod and main bearing wear, yes the crank has been flexing. I plan on just turning things down and getting some enjoyment out of it for a while.

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[RmvBfrFlght]

I think you have that backwards. Higher modulus of elasticity means higher stiffnes. Opposite of flexibility.

Well, SOB (that's an exclamation, not an adjective), you are correct. I do have it backwards. So the steel crank is over twice a stiff as the cast iron crank.

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