Rod Discussion

Post by **WDRacing** » Thu Aug 04, 2005 4:58 pm

As we know, Fiz just popped a motor do to Rod failure. What we don't know for sure is why the rod failed. I'd like to open a thread to discuss theory and ways to prevent stock blocks from giving up the ghost. Since I'm personally not ready for a built block yet and was planning on using 390WHP as a safe limit. Only based on the piston ring lands 400 ft lb of torque failure point. But with rods snapping at a known 420WHP, I figure we could all benefit from a discussion.

My theory, assuming the motor wasn't over revved, is oil starvation. Therefore causing the bearing to sieze on the crank and causing the rod to snap. Thats why it was such a huge amount of damage all at once. Rather then just bending a rod, it was completely snapped, leading me to believe it was a sudden force. Perhaps an oil jacket was clogged, or a bearing race became worn and overlapped the oil hole, both of which I've seen happen, only in the head area not the crank.

Anymore idea's??

WD

Post by **nissanfanatic** » Thu Aug 04, 2005 5:22 pm

Thats what I say too.

Post by **Nismo_Freak** » Thu Aug 04, 2005 6:37 pm

I disagree, the problem was not centralized to one single rod which seems to be the common failure on the KA in oil starvation situations (#2 cyl. being the most common).

Another reasoning is that I did not see alot of end cap destruction. Typically with the bearing getting spun you end up with rod bolt failure when it eventually seizes. All of the end caps I could make out were not destroyed, the opposite has been true for every oil starved KA I've ever seen.

Plus the rods all appeared to fail at their weakest point. With the car running a good amount of power for a span of time the previous stress cycling could have weakened the rods internally (hairline fractures, crystilline decay, etc.). Shotpeening will typically only case harden the rods structure, so internal stress damage is not fixed, but is masked.

Fiz needs to supply us with some main and rod journal pictures along with the rod, main, and thrust bearings. This will help to determine the source of the problem.

I for one am not a firm believer in the whole stock rod limit. Without knowing Nissans quality standards we could have a false understanding of what the KA motor can do. I say this as an external comment to brew some thought on the matter.

Post by **fiznat** » Thu Aug 04, 2005 6:41 pm

Okay, I can tell you guys right now that mine was NOT an oil starvation problem. The bearings that survived (even on the cyls that failed) are in VERY good shape. The worst of the bearing "damage" -- if you can even call it that -- is a little bit of "clouding" in the surface of the bearing. Truthfully I have never pulled an engine like this apart before, so I dont know exactly how theyre supposed to look- but I know for sure that they are pretty damn clean, almost a mirror surface on 95% of the surviving bearings.

I'll get pics, but honestly it doesnt look at all like an oiling issue to me. After tearing this thing apart, it looks very much like straight up rod failure.

Post by **Nismo_Freak** » Thu Aug 04, 2005 6:44 pm

fiznat wrote:Okay, I can tell you guys right now that mine was NOT an oil starvation problem. The bearings that survived (even on the cyls that failed) are in VERY good shape. The worst of the bearing "damage" -- if you can even call it that -- is a little bit of "clouding" in the surface of the bearing. Truthfully I have never pulled an engine like this apart before, so I dont know exactly how theyre supposed to look- but I know for sure that they are pretty damn clean, almost a mirror surface on 95% of the surviving bearings.

I'll get pics, but honestly it doesnt look at all like an oiling issue to me. After tearing this thing apart, it looks very much like straight up rod failure.

Fiz, please extract the rods and get pictures of them.

Close ups of the ends that failed if possible.

Post by **uncle_louie83** » Thu Aug 04, 2005 6:44 pm

i know his rods were prepped for the power...but we all know the rods can handle this power on the dyno...BUT...what i think is the longevity of the rods with say 400 plus horsepower. sure they can handle 400hp and i can go rip it up for a few months...mabye 6 months....but how long at this power rating can they handle the abuse? that is the question...whats the longest he has had these rods running this kind of power? i think the longevity of the rods at these power levels is what made this problem occur...

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

its like my old honda motors ive had...sure ive pushed stock LS b18a1 engines to 17psi at the track...on a damn good tune also...sure i drove them around 13psi daily driven...sure i could have had the rods treated so they could handle 20psi...but the thing is the metal could only take such abuse for so long of time

lewis

p.s. dont make me go into mathmatics here....lol...cause it will be a LONG post

Post by **fiznat** » Thu Aug 04, 2005 6:49 pm

Okay I went through my pics from today, looks like I only got 1 good picture of a "good" bearing. This one was probably the very worst of all of the ones that didnt get chewed up, a rod bearing on a rod that was otherwise completely destroyed.

It looks a little cloudy to me, but honestly that does NOT look like an oil starved bearing. Also take into account that some of that (minor) marring ("cloudyness" as I called it) could have occured secondary to the rods breaking...

Post by **PapaSmurf2k3** » Thu Aug 04, 2005 6:49 pm

I think im going to go with the prolonged power exposure theory. materials get fatigued over time. I just took an engineering class on mechanics of materials... it would be interesting to know exactly the material used for the rods, and to see a stress/strain diagram for it.

Post by **uncle_louie83** » Thu Aug 04, 2005 6:52 pm

those bearings look decent...now if those came from an engine that had not broken..like u were just taking bearings out for the hell of it...then id say the side wear is not good...looks like the main load was carried on the outside....but im going to say its due to the rods snapping and caused wear marks for now.

what kind of bearings were these. OE nissan replacements? or another company...let me know because ive had problems with federal mogul bearings before and switched to OE bearings and never had a problem since then.

lewis

Post by **fiznat** » Thu Aug 04, 2005 6:55 pm

The bearings are Clevite, professionally installed by my machine shop.

Post by **uncle_louie83** » Thu Aug 04, 2005 6:58 pm

machine shops will mic them properly and clevite is awesome its 99% sure its not a load problem on the bearing....thats got to be caused by the destruction.

like i mentioned and a few others have....its the abuse over time theory that comes into play

Post by **virus77** » Thu Aug 04, 2005 7:26 pm

WDRacing wrote: Thats why it was such a huge amount of damage all at once. WD

If Fiz's motor blowing was anything like mine, which it probably was because its pretty identical, I can tell you why there is so much damage. As my rod snapped the car ran for a a few hunders revs with a broken con rod still attached to the crank lashing out at the block and anything in its way completey destroying everything till the damn thing was shut off, mine had broken the cradle, punched a hole in the block, oil pan, and out the back of the block into the bellhousing area. After the hole was put in my block I cranked it once and it actually started and ran with a hole in the block and three cylinders (now thats a quality motor ). Also my bearings were in good shape aswell when I pulled the motor except for the one that the rod was missing(it actually made its was onto the Pacific Coast highway) and three of my other rods survived but one was a bit tweaked because of the whole incident. Save up for those rods kids, you'll be needing them.

Post by **cyrus240sx** » Thu Aug 04, 2005 7:48 pm

i would think it was just like what ivan found with his 240 except he replaced the rods b4 they broke... i think they started to bend just based on the power of the car and how much the car was driven, and when the couldnt bend any further... they snapped.... and to be on the safe side when building a turbo ka, if money permits, i would suggest that anything over 300whp and you should get new rods and pistons... but thats just me...

Post by **DammitBobby** » Fri Aug 05, 2005 2:27 am

I am curious as to how many KAT 400hp are built with aftermarket rods and how many miles have they have?

Fiz did you have the AEM logs available when the KAT imploded?

If it were me I would take the engine to the machine shop that built the engine and ask them what they think. Since you want to rebuild a new engine they may offer to do it for a reduce price or even better for free. The machine shop may have some good advice in how to prevent the implode from happening again.

Post by **DammitBobby** » Fri Aug 05, 2005 2:28 am

Thanks WD for bringing up this discussion as this can be a big concern to all of us.

Post by **WDRacing** » Fri Aug 05, 2005 3:02 am

For the record, those bearings are pretty worn for how many miles they saw. Good would mean no haze, I've oulled factory installed bearings from my RB20 with over 100k on the motor and had them look like that. But the motor was so destroyed it's hard to say what was the actual cause.

Why doesn't someone send me a stock rod and I have it crushed a my machine shop on base and record the pressure, then I'll have one stretched and record the pressure. Then one of you mathmaticians can hook us up with an equation or somthing.

WD

Post by **swwifty** » Fri Aug 05, 2005 6:48 am

Fiz, what exactly where you doing when the engine let go? WOT or just crusing on the highway?

Post by **fiznat** » Fri Aug 05, 2005 7:16 am

I was at WOT, but only for a couple of seconds... like I got up to 20 psi and then it popped, and ground, and shot parts out the back, and smoked, and and and...

Post by **superDorifto** » Fri Aug 05, 2005 8:40 am

now dont get me wrong, im still a noob here, but i helped fiz pull the motor apart, and like hes said this was not an oil starvation problem. the most violent damage looks like it happened in #1 and #4, hmmm... rods on the same compression stroke. there is so much talk in this forum about how much power the stock rods can supposedly take, well comming over from dsms i can say that talk is cheap. stock mitsubishi 4g63t rods look almost identical to KA rods and are SUPPOSED to be able to handle 400+hp. they too sometimes fail due to nothing other than stress and fatigue. regardless of how much "hp" these KA rods can take, there are ASTRONOMICLE forces at work on every part in that motor. at 20psi the amount of heat being transfered to the rods, along with the stress of actually going through its stroke, seems like a little too much for the poor rod to handle. and its not like all 4 of the rods just let go at once, ONE let go, and the resulting chaos made metal soup in his oil pan. the bearing sufaces on the crank and girdle looked super clean, at least whats left of the girdle....bottom line is that with foster,s set-up there was only one weak link. and he found it. I vote for thermal fatigue induced failure.....

Post by **swwifty** » Fri Aug 05, 2005 11:33 am

I'd agree with the rod failure theory. Got any good pictures of the rods that failed Fiz?

Post by **fiznat** » Fri Aug 05, 2005 11:47 am

Yeah. There are more pics of general damage in the other thread about this, as well.

#1:

Still in the block, it broke in half and bent in towards the countwerweight, locking itself there. I'll get it out later.

#2 actually survived completely whole with only very minimal damage:

#3 was not so lucky.

#4 looks like it almost snapped, but didnt. It is twisted at a couple weird angles, and banged up quite a bit.

The rod caps broke off of the crank completely on #1, #3, and #4. #2 was the only rod to remain attached to the crank (and piston). Note also that some of rods #3 and #1 are lost... possibly on the highway.

EDIT: Hey guys, like my new sig?

Post by **PhastKA-T** » Fri Aug 05, 2005 12:23 pm

Loads on the rods are crazy with the high stroke to begin with. Add some mass on the end of the rod (heavier than stock forged piston and wrist pin) Spin the motor a bit higher in the RPM range and loads go up exponentially.

Long stroke and huge rod ratio mean dwell time at TDC is LONG. Just a bit too much timing and your going to detonate and bend a rod.

Fiz had ARP bolts in the rods but had no other prep done to them.

Questions for Fiz:I believe you told me on the phone that they were "factory reman rods" Is that correct?

Were the small ends pin fitted for the full floater pistons / pins?

What kind of knock numbers were you getting on the AEM?

What kind of timing were you running in the 20 psi cells?

Post by **fiznat** » Fri Aug 05, 2005 12:49 pm

PhastKA-T wrote:I believe you told me on the phone that they were "factory reman rods" Is that correct?

Yep!

PhastKA-T wrote:Were the small ends pin fitted for the full floater pistons / pins?

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...

PhastKA-T wrote:What kind of knock numbers were you getting on the AEM?

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

PhastKA-T wrote:What kind of timing were you running in the 20 psi cells?

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...

Post by **onosqv** » Fri Aug 05, 2005 2:06 pm

Wow Foster, those pictures you took (even though it's very sad) are absolutely stunning quality. The detail is just ridiculous.

Just had to say it. Good thing I won't be hitting 300+ any time soon, haha.

Post by **TheOne** » Fri Aug 05, 2005 2:14 pm

so how many miles did the rods have?(assuming you used yours but shotpeened them), to me it sounds like stress, cause well the pistons weren't bad so it doesn't sound like detonation.(maybe check the spark plugs?)

and damn fiz did that do so much damage, i mean i've seen ford 305's in 2 halfs(2 much hp), but not rods so damaged.

Post by **virus77** » Fri Aug 05, 2005 2:54 pm

Damn my damage was pretty minimal compared to yours but this piston looks like yours , its the center piece on my shelves in my bedroom now, good momento.

Also here you can see a good shot of the crank with the entire rod missing.

Do you think the end cap on the stock rods could be the problem. When mine blew it was about half a minute after some WOT runs while coasting at 3 grand. I heard a small rattle and then all hell broke loose within seconds after the rattle. Is there a posibilty the rod end cap came off, or worked itself loose (ARP rod bolts) then broke. My thoughts were that at first but then I figured they slightly bent under power and snapped after running bent due to a stress fracture. Actually, I also had my theory that when my timing chain broke and my valves hit the pistons it caused them to tweak a bit and eventually break, a possiblity as well in my case.

Edit: Sorry about that, I forgot to resize.

Modified by virus77 at 2:54 AM 8/6/2005
Modified by virus77 at 2:55 AM 8/6/2005

Post by **WDRacing** » Fri Aug 05, 2005 3:14 pm

Virus, I deleted your one pic, it was too big and made the thread a PITA to read. Resize and repost if you want to.

Post by **toki** » Fri Aug 05, 2005 9:06 pm

on the subject of rods, eagle is officially the slowest company on earth,

4 months ago, while I was living in canada temporarily, dreaming of my rebuild, they were 4-6 weeks from release.

4.5 weeks ago, when I called them again, they were 2-3 weeks from release.

Today, with a half torn down block and school approaching quickly, they have no release date set, which means they won't be released any time in the next 30 days.

But on the good news, someone told another ka-t enthusiest on the phone they were rating them to 1000hp. Which ya know...gotta take with a grain of salt. But still. C'mon. <$400 for a set of good rods with ARP hardware. I'll take it! (P.S. no "omg eagle sucks dude" comments neccisary, we know they made one bad batch of DSM rods like 10 years ago, the rest of the world is over it and you should be too."

Oh eagle, you are a harsh mistress.

Post by **IvanAtSPRacing** » Sat Aug 06, 2005 4:27 am

fiznat wrote:#2 actually survived completely whole with only very minimal damage:

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?

fiznat wrote:#3 was not so lucky.

The rod caps broke off of the crank completely on #1, #3, and #4. #2 was the only rod to remain attached to the crank (and piston).

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.

Post by **fiznat** » Sat Aug 06, 2005 5:50 am

IvanAtSPRacing wrote: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?.

The rod moves back and forth freely with no binding at all, the wrist pin moves with the rod and I can easially move the rod side to side on the pin with very little resistance.

IvanAtSPRacing wrote: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.

I can see a bunch of the bolts in there-- donno if I have *all* of them but definitely a good portion. I will collect them all and take a pic.

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