Prevented a Broken Crank???

[super diesel]

Got the motor out and found the second from the front Main bearing spun pretty good. The bearing was pretty well chawed up. Way undersize at this point. The main cap and block journal seem ok (going to check out of round on the crank and main). This was noticed at first at very low RPMs (about 1200) when I first started to take off. I was only 2-3 miles from home and made it ok, but it did get worse with distance (maintained low RPMs and speed). What I'm thinking is this. I've seen others with spun bearings here a well as the location of the majority of breaks (or am I way off?). I'm thinking at much higher RPMs if this bearing spins and gets chewed through in a matter of revolutions from the pressure, what would happen next with no support under it when power is being applied. Anyone else see signs of a spun bearing with the broke cranks? Could this be an oiling issue at this area?

 

[LBZ]

........Anyone else see signs of a spun bearing with the broke cranks? Could this be an oiling issue at this area?

opcorn:

 

[super diesel]

By the way. This was a fully balanced rotating assembly.

 

[Alligator]

Mike (MMLMM) spun the front main bearing on his 08 LMM. Here's what the bearing looked like.

He did not break the crank though, but he did drive several hundred miles with the bearing spun.

 

[Alligator]

 

[super diesel]

OOOOH! That's ugly. The out side of mine were fine, but the insides were chewed up good. Were you able to reuse the crank? Was it still round? How were the journals?

Also, for those wondering. I did this on stock injects. The Kermas aren't in right now and this motor had 15K on the build. I just had got done runing at 3100-3200rpm up the back side of vail (a 11K elevation pass in CO that takes about 10-15mins to get up at practicle speeds) with alot of weight in 3rd gear 60miles previous.

 

[Alligator]

OOOOH! That's ugly. The out side of mine were fine, but the insides were chewed up good. Were you able to reuse the crank? Was it still round? How were the journals?

Also, for those wondering. I did this on stock injects. The Kermas aren't in right now and this motor had 15K on the build. I just had got done runing at 3100-3200rpm up the back side of vail (a 11K elevation pass in CO that takes about 10-15mins to get up at practicle speeds) with alot of weight in 3rd gear 60miles previous.

That block is sitting in Mike's garage, and we put a New GM crate motor in it's place. The journal looked like this, I believe it has too much damage to be reused.

 

[Alligator]

And if you look closely at the bottom picture, several of the teeth were chewed off the crank gear for the oil pump.

 

[super diesel]

How were the rod bearings on the row behind it after that since they get fed from those crank oil passages. Any were signs there?


Make no mistake that this thread is in ALL seriousness. It's not in any way to take away from the injector stuff which in no way do I think out of balance injectors are good for the motor and the balancing of them is a good PM. Just trying to find more root causes of the broke cranks since alot of times this doesn't discriminate between stock and moded motors.

 

[slowlmm]

How were the rod bearings on the row behind it after that since they get fed from those crank oil passages. Any were signs there?


Make no mistake that this thread is in ALL seriousness. It's not in any way to take away from the injector stuff which in no way do I think out of balance injectors are good for the motor and the balancing of them is a good PM. Just trying to find more root causes of the broke cranks since alot of times this doesn't discriminate between stock and moded motors.

where you running arp main studs or any aftermarket stud?

 

[super diesel]

where you running arp main studs or any aftermarket stud?

No. Stock bolts. I don't think there was ever enough power put through this one yet to test the need for studs. However the reference I use is the power others have been to with stock (N2O) and moded motors. So whats the real point we need them at? I've heard of Guy seeing mains that have moved with motors before. Were they stock or not and how much power had they been to? I don't know. I believe this was an oiling issue, but could be wrong.

 

[MMLMM]

Rod bearings were fine. The only issue whs that main. Also the oil pump gear. Not sure if the oil pump gear went first then it caused a main to spin.


After running the track in bakersfield, I noticed a drop in oil pressure and a noise about 3/4 track, so i let up. Pulled into the pits and it sounded like a bird chirping. Truck seemed to run fine though. The next day we all drove to the Mcrats for the party, a few listened but couldnt figure out the sound. (it sounded like a spun bearing to me, but everyone i talked to said that is very rare). I drove from Ca. back to Vegas with the spun bearing sound.....and no oil pressure at idle.

 

[super diesel]

Just discovered something I think is a design flaw (it's on both my blocks and the one in the pics is the same). I will need to research a little before I let this cat out of the bag. It's not looking good and I'm really surprised we haven't seen this more with what I found. We may need to correct this on future builds and when folk have a motor out for repair.

 

[Alligator]

Let us know what you find, I'm going to start my build this winter, and don't want any surprises.

 

[super diesel]

Will do. I guess I shouldn't call it a design flaw because I think it's ok for the stockers (not the best design by any measure though). I will be modifying the main caps as well as a small portion of the bearing for the fix. This is the simplest fix I could think of for it with out moding the block.

 

[slowlmm]

No. Stock bolts. I don't think there was ever enough power put through this one yet to test the need for studs. However the reference I use is the power others have been to with stock (N2O) and moded motors. So whats the real point we need them at? I've heard of Guy seeing mains that have moved with motors before. Were they stock or not and how much power had they been to? I don't know. I believe this was an oiling issue, but could be wrong.

I had sighns of movement when i tore my STOCK motor down for my rebuild. No nos ever
highest rwhp was in the 600 hp area

 

[ripmf666]

Will do. I guess I shouldn't call it a design flaw because I think it's ok for the stockers (not the best design by any measure though). I will be modifying the main caps as well as a small portion of the bearing for the fix. This is the simplest fix I could think of for it with out moding the block.

Michael I think i just saw what your thinking has to do with the bearing location and the crank oiling hole and were the bearing is located on the cap and block.I will dig some pics up to point out what I think you are looking at. That and its a small surface area on the bearing to take all the load.

 

[ripmf666]

 

[super diesel]

This area is also a concern but no near future fix if the bearing companies aren't willing to partake. For one Henry, I don't like the fact that the load width area on the main bearing is the same width as each one of the rod bearings. I would like to see 50% or more area here and I raised this point a few years back as well. There's a greater concern to me now though, but I need to talk with a few others on this first that are more knowledgeable that I at HP motor building that my not have see this in the same light as I. It may help bring the crank failure factor and reason to light.I don't think it's an oiling issue any more unless the passage gets blocked. To many "same area" failures for it to be that.

 

[wdino73]

I did all the right moves with my build used great parts took extra time with the build to make sure everything was perfect as could be expected, we very particular with the breakins I feel I did everything right but with only 2300 miles on my new fresh engine, I broke my crank, DAMMIT. I didn't race, pull, street race, nothing this is bullshit, any advise, things to look for when I tear it down, I'm looking for answers, I was using a Fluidampr, I hope that was not the problem, the rest of my specs are in my signature, any words of wisdom would greatly be apprieciated. I believe it's my crank I pulled the damperner tonite and you could move the crank snout, maybe it's not broken that's probably wishful thinking