Rod Discussion

[Nismo_Freak]

Fiz, pivot the rod back and forth on this assembly how does it feel? Is it nice and loose or does it kind of bind? Watch the wrist pin when you move the rod back and forth. Does the wrist pin move with the rod or with the piston? Can you slide the rod side to side on the wrist pin?

What concernes me is why the rod caps came compleatly off. I am wondering if there was an issue with the rod bolts. Most of the time when you break a rod, you end up with the big end still stuck to the crank (like your #2) Can you find the rod bolts from 1, 3, and 4? Take some pix.

Ivan on one of the pistons there was significant blueing and friction on the wristpin. It's in a circular pattern and doesn't have alot of strike damage from when the piston decintegrated. From the violence and the bending seen on some of the rods (smooth bending), it seems likely that one or more of the wristpins could have seized, caused the small end rod bearing to seize from the added stress, and ultimately rod failure. That would cause the rod to snap, and I'd imagine the piston would also shatter.

On one of the rods there is some casting text down the side of the groove. The final Nissan logo appears to be stretched and drawn at an angle. This could elude more towards snapped rod as a result of some other friction source perhaps.

More about the rod caps, if you look at the destroyed rod, the lower cap is bowed outwards and the upper cap is coned. This obviously shows where the rod bolts attempted to keep the assembly intact but there was a very strong resistance force (blueing of the bearing also shows high frictional load). There is a disparity between the planes when you look at the upper and lower connection points for the rod bolts. While they have excellent torsional and linear rigidity the rod bolts are not made to withstand a sheer load from the caps migrating.

My .02 cents, alot of it could be speculation but sometimes it's something to think about.

[superDorifto]

the rods looked bent and stretched, but the question of when the damage happened will probably never come clearly into focus. Yes the rod bolts sheared off, I held one and it was snaped right where the treads started. the question is...did they shear because of forces in the motor, or because of debris damage. the girdle was in at least 5 pieces, and some of the rods look like they struck other hard objects then the block. Im not gonna link to the pics again, theyre in the thread a lot already. look closely, there are dents that look like they could have been caused be debris lying in the path of the rotating assembly...again telling me that it was a small failure that quickly snowballed out of control....how long are rod bolts going to stand up to the shearing forces of the rods slamming into other pieces of metal??? Not very long, even if they are ARP...my 2cents for the day...

[superDorifto]

there was no "friction source" by the way, all the wrist pins that are left are in good shape, as are the crank bearings. it looks like a rod just gave up the ghost. i find the idea of oil starvation a dead end, because EVERYTHING in teh motor was new, and installed professionally. This motor wasnt assembled by a blind retarted monkey, it was built by one of the best builders in CT.

[projectka-t]

Does anyone think it may be linked to the "no breakin-breakin" Im just tossing out a few idea's I have had since I read what happened.

[fiznat]

Who knows. Its pretty much all speculation at this point I think. We can make some educated guesses, but I think the best thing to do is have the engine seen by a professional and in-person. I am doing just that this week, so hopefully we wll have some at least semi-solid answers soon.

Ivan, I'm gettin those rod bolt pics... just havnt had time yet. Thanks for your input on this, I appreciate it.

[nissanfanatic]

tracking down causes of engine failure

Namely this part:

Quote »Too much heat in an engine can cause serious problems because heat causes metal to expand. The hotter the engine gets, the tighter clearances become until there are no more clearances left. Overheating can cause valve stems to gall and stick, and pistons to scuff and seize. So if you see either of these conditions when you tear the engine down, it’s a pretty good clue that overheating caused the engine to fail.[/quote]Overheating a possibility?

[C-Kwik]

think about the LOOOOOOOOOOONNNNNNNNNNNNNGGGGGGGGGG *** stroke we have on our motors....im sure there is some piston slap going on at very high rpms...i think due to bore & stroke...also power levels and the metal processing it went thru was just too much. like said...longevity

But, the KA has a very good rod ratio. This is really the important part in analyzing rod side load and piston side loads.

[C-Kwik]

It is possible detonation could be a factor. With forged pistons, the pistons can withstand quite a bit more detonation before chucks of metal begin to disappear. Pull the plugs. If the cylinders didn't get too contaminated, you might see a light metal flake appearance on the electrodes and insulation. This might give some clues. In any case, if this was a compressive failure, detonation could have been a factor that pushed an already high strung rod(s) over the edge.

From what I can tell, it looks like each rod saw some amount of twisting and bending. Similar to what we saw in Ivan's examples of the stock rods.

The rod bolts and end cap failures can be the result of collateral damage. With so many chewed up parts, it looks like the rod ends attached to the crank may have been taken on a ride for several RPMs.

IT would be hard for any of us to really come to a conclusion without analyzing the entire assembly as an expert would likely need to do the same. Espectially considering it does appear that there is a lot of collateral damage. This can be a fun discussion though.

[C-Kwik]

Does anyone think it may be linked to the "no breakin-breakin" Im just tossing out a few idea's I have had since I read what happened.

No. The break-in that is most important is the piston ring-cylinder seal. And generally a poor break-in here would just lead to poor compression. The rest of the motor should still function fine.

[dsylvia]

how was the timing? would not pulling enough timing while boosting cause something like that?

im just throwing that out there, seeing if it sticks, lol

[fiznat]

Pics as requested. I dont have a macro lens so these are kinda not ideal pics, but you get the idea:

Plugs. I think at this point we can pretty much rule out detonation? They look like nothing happened...



Rod bolts. Sorry Ivan, these are all I could find right now. No idea what went with what, they were all in the oil pan. #1 rod is still attached to the crank, Its gonna take some work to get it out because everything is so mangled. Ill post more if I find em, but I think this is the general idea.

[fiznat]

how was the timing? would not pulling enough timing while boosting cause something like that?

I dont think so. Timing too far advanced would cause detonation, which I have yet to find any evidence of.

[superDorifto]

wow, i cant believe thats all you could find for rod bolts....guess the rest are on rt 9 somewhere...

[huguetpj]

Hey fiz... quick question... what do you mean by 'factory reman rods'?

[Tulsa_S-13]

I think he means factory rods that have been shotpeened. Correct me if I'm wrong.

[deezlins]

I thought you guys would be interested to know that one of my friends has been through 6, thats right 6, naturally aspirated KA's. On every one he checked the #3 rod bearing went out.

[MarkEmark]

I thought you guys would be interested to know that one of my friends has been through 6, thats right 6, naturally aspirated KA's. On every one he checked the #3 rod bearing went out.

Wow, sounds like a definite case of OPERATOR error.

If you put the engine through hell and back and don't care for it (ie, over-revving, not changing oil regularly, not checking out vital signs), they're not gonna last. Nothing's bullet-proof.

Maybe after the 5th engine your friend started treating it differently?!?

[deezlins]

Yeah it probably was operator error, because he kept getting cheap used motors and gave them relentless hell, but i was just saying, in all of them (except maybe the last one, havn't checked it yet) the #3 rod bearing went out

[rn240sx]

My opinion....

The stock rod gave out eventually...

It was just a matter of time. Regardless if it was shotpeened from the factory or by a machine shop, they can only hold so much force b4 they bend or snap..

Hell, Pauter rods claim to handle 800 hp... And im sure once u go past that mark, those are bound to bend or snap as well..

Because of this un-fortunate event, im getting a set of pauter rods as what my machine shop guy KEEPS telling me to do. But my goal is 400 whp.. and no more.

[Checkered-Member]

The main question here is how much can the stock rods handle?

Well handle is a relative term, I bet they can take 600whp for 2 seconds and 120whp for 250,000 miles.

The KA rods are designed to handle 130whp for a VERY long timeAs power increase life span decrease, if you want a long life span (close to stock) on a higher power KA, you got to pay up.

For my turbo project, I upgraded my cooling system, brakes, suspension, transmission, and soon to be upgrading the engine, all this to only run 12psi, why? Because my goal is close to stock life span with twice the power.

[C-Kwik]

The main question here is how much can the stock rods handle?

Well handle is a relative term, I bet they can take 600whp for 2 seconds and 120whp for 250,000 miles.

The KA rods are designed to handle 130whp for a VERY long timeAs power increase life span decrease, if you want a long life span (close to stock) on a higher power KA, you got to pay up.

For my turbo project, I upgraded my cooling system, brakes, suspension, transmission, and soon to be upgrading the engine, all this to only run 12psi, why? Because my goal is close to stock life span with twice the power.

If a rod will handle 600 HP for 2 seconds it should handle it for as long as the rest of the motor stays together. Compressive rod failures occur from too much force. There is no fatigue in the metal due to compressive forces. It will bend or break at the point there is too much force. Tensile forces can cause fatigue however. But tensile forces only go up if you rev higher. That is the only factor that will change tensile forces. You can add 10,000 HP to a motor and if you keep the maximum RPM the same, it will not see any additional tensile load on the rods. So fatigue is not an issue. Power handling from a compressive load standpoint is.

[MarkEmark]

Hey guys,

yeah my engine just blew up too. Fun stuff. Rod failed at 16 psi @ 3500 rpm from a tiny *** turbo.



Enjoy

[Thee 240sx Owner]

Yeah it probably was operator error, because he kept getting cheap used motors and gave them relentless hell, but i was just saying, in all of them (except maybe the last one, havn't checked it yet) the #3 rod bearing went out

Same thing with me.. i've been through 5 KA's 4 being SOHC and i spun the bearing on #3 cyl in 2 motors... so maybe it is a problem... i was also beating the hell out of mine

[huguetpj]

If a rod will handle 600 HP for 2 seconds it should handle it for as long as the rest of the motor stays together. Compressive rod failures occur from too much force. There is no fatigue in the metal due to compressive forces. It will bend or break at the point there is too much force. Tensile forces can cause fatigue however. But tensile forces only go up if you rev higher. That is the only factor that will change tensile forces. You can add 10,000 HP to a motor and if you keep the maximum RPM the same, it will not see any additional tensile load on the rods. So fatigue is not an issue. Power handling from a compressive load standpoint is.

What about the slightly bent the rods that, I believe, Ivan took out from one of his shops KAts? Detonation? After some point rods would start to slightyly bend until they snap... because of too much stress. Maybe I'm just not thinking clearly.

[:: orion ::]

Sorry to bump this after a fews days of it laying dormant...but:

Has anyone weighed aftermarket forged pistons as compared to OEM?

The JE's that I have laying around (from DaveEEE's old motor) seem quite a bit heavier than OEM pistons...which could EASILY be the reason a rod would fail.

Reason I ask...I've been revving to +7000 and running ~300rwhp for years, with racing/HPDE abuse...and haven't experienced a failure. But guys with (I suppose) heavier forged pistons on the same rods are breaking them at lower RPM's.

Any thoughts?

Anyone care to weigh one of their forged slugs? I'll take on of the JE's and a stocker to the post office later if I have to, to get a measurement in grams.

- Brian

[duncan351]

Yep!

I think so. I'll have to doublecheck with the machine shop on this one, but I remember something about that. Sorry, I'm still learning with this machining stuff...

I wasnt datalogging when this happened, but I never ever saw any significant knock. Note below.

I dont have the map in front of me so I may be off by a degree or to, but I think it was in the 17* area or so with the methanol.

You seem to be asking questions leading up to the conclusion that this damage was caused by detonation. I dont think that was the case at all. Maybe you didnt see the other thread about this, but check out the pistons:



Ring lands looked 100% as well. Again I am not very experienced with this I admit, but it doesnt look like these pistons saw very much detonation at all...

Its possible to detonate without messing up your pistons. Just means you didn't detonate to that point or you didn't detonate enough to mess up a piston because the rod gave before then. What size turbo are you running? Where you on pump or race gas? I assume pump since because of your timing @ 17 degrees. Is this correct?

[fiznat]

I was running 93 pump gas, but I also have a methanol injection system spraying a 50/50 meth/water mix. Turbo is a T3/T04E .50 trim.

I posted this in another thread (maybe I should make another just to consolidate), but I took the motor to my machine shop and I was told my by machinist (who has 25 years experience and I treat his word as gold) that detonation was NOT a factor in this blowup, nor was oil starvation. Not only are my pistons fine, but the spark plugs look perfectly normal as well. I even rechecked the gap, and it is within the spec that I installed them at. Youd think any detonation strong enough to bust rods would certanly "regap" my spark plugs at the very least, but that didnt happen...

[toki]

so basically what it is comming down to is either your rods has stress fractures that either wern't detected, or you didn't have them checked for, or your 25 years experience machinist didn't properly install them (unless you installed them.)

[:: orion ::]

Has anyone weighed aftermarket forged pistons as compared to OEM?

The JE's that I have laying around (from DaveEEE's old motor) seem quite a bit heavier than OEM pistons...which could EASILY be the reason a rod would fail.

...

Anyone care to weigh one of their forged slugs? I'll take on of the JE's and a stocker to the post office later if I have to, to get a measurement in grams.

Allow me to quote...uh...myself. Hehe.

Well, I weighed the stockers and the JE's (8.5:1)...remoived all the rings, weighed them with and without the wrist pins.

Stock: 1lb, 0.8oz with wrist pin...13.1oz, piston only.

JE: 1lb, 0.8oz with wrist pin...13.1oz, piston only.

Exactly the same.

Nevermind that theory.

- Brian

[fiznat]

hahaha! Good idea though, I'll do the same with the Ross once I get mine in-- and I'll verify that weight with the stockers I have laying around.