Wishmaster's87IROC

iTrader: (4)

Ok im sure some of you guys seen the thread about the clanking noise when reving above 3000grand.... well here it is!
I went and talked with the motor shop and this is the time of year that they are swamped so he told me to take the oil pan off and check the bearing but he first assured me that the bottom end would be fine so I checked only the #7 rod bearing cause thats where I knew the sound was coming from. It looked fine. So I went ahead and removed the head and found the problem.

I dont know how many of you remember my spun bearings problem that I had months ago well the number 7 was the worst and had been slapping the head. You can still see the mark on the piston. Im guessing that is was caused the piston to become fragile and broke....buts is it odd to break where it did? Would that cause the clanking sound that I heard?

Also what happened to that part of the piston? did it just become dust and go out my exhaust cause I didnt find ANY metal in the pan or anywhere in the block.

Recap: heres the vid of the sound


and here is the piston




the top ring does not move like the others rings.

Im going to call KB and see if I can buy one piston cause I cant afford to buy all new pistons. ANyone know where I can buy 1 piston? I need a KB-122

Wishmaster's87IROC

iTrader: (4)

what would that cause? other than the obvious, would that cause me to lose oil? run rich?

what?

onfire

Wishmaster's87IROC,

Wow how about that! Thats no fun man but at least you found it out now rather than on a wot pass.
Of what it sounded like it didn't sound like a knock(faulty rods) ... sounded higher pitched ... did you get a chance to take a peek at your other pistons? Was your head damaged from the piston fragments??


Rabi C.

Wishmaster's87IROC

iTrader: (4)

the other pistons look fine. i didnt pull the other head. THe underside of the head looked fine that I can tell...theres no pits or anything that looks like fragments beat all to hell on it. thats why Im wondering where the frags went to?
But yeah once I heard the noise I never drove the car again, I didnt want to make it worse than it already was. Whats wierd is that it never made that noise before and then I took the motor out to fix an oil pan leak and replaced my 1.52 rockers with 1.6's and soon after is when I heard the noise.
Im sure its wasnt cause of the new ratio. I guess now that I have the head off I can make sure I have enough clearance for the 1.6's

but where would the piece of piston go?

Sonix

iTrader: (1)

Whoa, where is the piece of piston? Hows the cylinder wall?

That might have chipped off when you spun the bearing, I forget, did you remove the heads then?
Any heat marks on the piston, discoloration? It's hard to tell since it's been beat to crap for so long... Good thing you took it apart eh?

Look at the valves on that cylinder *very* closely. Check the head over carefully.

Well, at least you found it eh?
See if Ohio crankshaft will sell you one. Then try to match the weight vs the rest.

mw66nova

iTrader: (13)

i'm almost positive that you can buy single pistons through summit or jegs.

Wishmaster's87IROC

iTrader: (4)

yeah when I spun the bearings I had the whole block redun cost me $1200 or so. Everything redone. New crank, re-conditoned rods but I used the same pistons. THey put together my short block and said everthing was fine. I only have about 300 miles since the rebuild.
Cylinder wall looks fine.
whats Ohio's website?

Wishmaster's87IROC

iTrader: (4)

OK I went outside and checked out the cylinder walls of 7 and 5
#7 which had the broke pistons has slight up/down marks where as #5 still has the side/side marks from the hone. Maybe some of the piston fragments did make it down the wall but most of it Im thinking is powderized on top of the piston. compared to looking at the other pistons. Its just mixed with all the carbon.

heres some pictures.

side skirt on #7


#7 cylinder wall


#5 cylinder wall


#7 valves on head

afida15

man that really sucks. but look at what one of my pistons looked like when i ripped my motor apart lol

ryan91rs

iTrader: (1)

might get away with just honing it and then reassembling.

mw66nova

iTrader: (13)

these are my thoughts too. i'd definitely hone that cylinder and put a fresh crosshatch in it for positive ring seal when you put it back togehter.

sofakingdom

iTrader: (1)

I guess we all assumed that when whoever "repaired" whatever went wrong before, that they would have caught that sort of thing, since that's what you were paying them to do.

Oh well. Now you know why I build my own.

Wishmaster's87IROC

iTrader: (4)

what the hell you mean MIGHT get away with JUST?!!!!
like what the hell else would be wrong and have to be done?

if I honed just that one cylinder I would have to disassemble the whole motor? cant it just be lightly honed while covering everything under the cylinder and all around it? then cleaning it out real good?

and what IF I didnt hone it? what kind of problem would I run into?
----------
would detontation have caused that??????

sofakingdom

iTrader: (1)

like... 7 other cylinders, as well as lots of other parts.

As far as just fixing that one defect, then yeah, replacing, honing etc. would take care of it. But there's still a risk that there's other problems in the motor; metal shavings in the oil passages, other parts that got stressed, other things that didn't get put together right, and so on.

It's a risk, not a certainty. It's entirely possible that the whole rest of the motor is perfect. On the other hand, it's entirely possible that you can fix that one cyl perfectly, and in another 300 miles, you'll be right back again to where you are now because some other detail had got overlooked. Which is not a trivial thing; seems like overall there has been a great deal of overlooking of details by your builder.

It's a judgement call. No one can tell YOU how certain YOU have to be that everything is in order inside it. YOU have to be the judge of that.

That's why the correct word is "might".

Guest

Time to turn the block upside-down and shake everything out of it and start over.

That type of failure could be previous damage, or the ring ends could have butted and caused that. Those are the infamous KB hyperubreakits. Were the rings replaced? Did they PROPERLY follow the KB ring gap instructions? If they just took a set of rings and threw them in there, I'd say thats 99.99% the reason you're in there yet again.

BTW, dont call your builder. Pull another piston, take off the top ring carefully (dont break it), and measure the end gap for yourself. It needs to be about .025 MINIMUM. Any less and that was the cause. You may be able to take the ring off that busted piston, but make sure it isnt all messed up where the gap is.

1989GTATransAm

iTrader: (3)

I just saw a KB hypereutectic piston that completely shattered. Metal throughout the motor. He will be going with forged pistons. The other seven pistons look just fine. This was after 5000 miles on the motor.

Sonix

iTrader: (1)

As max mentioned KB pistons spec a MASSIVE ring gap compared to what other companies recommend. I like it, they even give reasoning as to why. If you think about it, a larger ring gap contributes to a miniscule (teeny tiny) extra amount of blowby and extra oil consumption. I think at about .080" ring gap oil consumption started to become "noticeable", 1 quart between oil changes. This is according to their website.

Anyway, if too small ring gap did have something to do with it, as sofa mentioned, you'll want to check the other 7.
You're now acutely aware of how much of a PITA it is to pull the engine. Is it harder to pull it again later, or pull the entire rotating assembly now and re-gap rings, hone cylinders, and scrub the block clean?

Cam, rod, main brgs, summit house brand - $40
cam galley plugs $6
gasket set $100 max
Piston $50 maybe?
Ring set $80

I think you're getting out fairly cheaply actually. A 3 stone honing tool was $40 when I bought one last year. Cam bearing install tool is $60, but you may be able to borrow/rent one.

Count your lucky stars you don't have a bent crank (requires a new crank *and* a new $300 balance job), or damage to the heads.

five7kid

iTrader: (14)

Count me as another who assumed "rebuilt" meant "rebuilt", not "reassembled".

I don't think I would settle for anything less than a full new set of pistons and rings. Complete disassembly, cleaning, checking, glaze break would be my plan.

sofakingdom

iTrader: (1)

The biggest potential problem IMO, is that they left the ring gap too small; like it should be for typical cast or forged pistons. If that's what was done wrong, then all 8 were built essentially the same; and all 8 will fail the same way, sooner or later. This time, the one that had the least end gap, protected the other 8. Next time, it'll be the one with the next closest end gap.

If it was mine, I know EXACTLY what I'd do. And while I might very well just hone the walls (I'd do all 8) and replace just the one piston, it would get torn ALL THE WAY down; rifle brushes run through the oil passages, with the cam bearings and all the plugs OUT; and reassembled with new rings and bearings, and the correct attention to the details. But that's just me... you gotta be the one to make the call on your own motor.

Keep in mind also, that if you do that, you're only $50-100 away from having your compression problem GUARANTEED TO BE SOLVED CORRECTLY. Again, if it was mine, I know what I'd do. I HATE doing the same thing twice - or more.

Supervisor42

I have done plenty of re-ring jobs and used just my fist surrounded by 400 paper in a figure "8" up and down motion to break the shine off of used cylinders. All worked fine without blowby or oil consumption. Just hose down the rod journal with solvent then oil before you put the pistons in.
If you don't scuff the shine off of the cylinder, the rings will never seat and it will have blowby and blue smoke.
This is not to be confused with "just-been-bored" cylinders which MUST be honed for size and finish.

>would detontation have caused that?????
I thought this was the #7 piston that was smacking the head when the bearing spun? That would have caused it...
EDIT: the missing part of the piston went out the exhaust valve on the first try.

Wishmaster's87IROC

iTrader: (4)

ok heres the deal...I got lucky with only ****ing up one piston if you can call it that....even luckier that apparently the piece went out my exhaust and didnt damage anything else.
Check this out http://www.kb-silvolite.com/clearance_pop.php
that looks just like mine.
Anyways after speaking with KB they listed alot of reasons that could happen... ring end gap,to much advanced timing, detonation, tune, rich, lean and so on. 1,2,3 are the main ones.
I took the piston up to the engine shop and first thing he said when he saw it was detonation. he pointed out all the hot spots on the piston. I had been up there when I had a detonation problem weeks ago and they told me to FIX that before I screw something up. He then measured the piston and found that the skirt diameter was way off. I went home and took the rest of my pistons out and took them back to the shop so he could measure the skirts and look at the tops and rings. They are were all fine and within spec. The ring was was a little shy .024 so I had him open up the other top rings to .032 which was the recommended gap from KB for nitrous use.
I aksed about honing and showed him pictures and he said Im fine to just scuff the walls with some scotch brite pads and wash them out. I did it alitte when I got home jsut to see and in the #7 the marks were so light that one swipe of the pad and they were gone.... ALL bearings were fine.. cams, mains, rods everything. There is not one piece of metal in the pan or anywhere that I can see. KB and the engine shop both said that it blew out the exhaust and/or just powderized in the cylinder and went out the exhaust. Remember I didnt drive the car at all once the sound was heard.
THe engine shop http://www.buckracingengines.com/ didnt cut corners on my block didnt put something together wrong or anything on my rebiuld they did what I paid for..those guys up there are extremely nice southern hospitallity and will do alot for me but that is a business and cant do anything for free which I understand totally...they let me have the piston installer and told me bring it back when Im done....all this was my fault with the detonation problem I had awhile back ago. Leason learned I guess.

Im new to all this motor rebuild, put together, take apart, all the stress...and its worse cause I went broke screwing with this. But oh well!!!!! once its done it should be done. YEAH RIGHT!!!...LOL

I need a KB 122-12 590 wieght right side piston.

I also need 1 set for 1 piston of Plasma Moly rings.

One thing I did fine out was that I have .040 pistons which puts my specs at 385ci I thought I had .030 SO now that actually raises my Static and dynamic compression.

anyways.....that where I stand at now, I called JEgs about the piston and ordered but wont be here til next week they didnt have it in stock so have to get it from KB.

Now I need the rings, anyone know where I can get just a set for one piston?

I do value you guys here and the advice that you have given me on the nightmare...ALOT! but sometimes ...damn!

and I know you get a kick out of all the probmes I have....but Im sure I have helped some people out on here and made sure they dont do the mistakes that I have done. LOL!!.......they pictures do tell alot and help out alot on here too.

90c350

I would have to say that the reason that this happend is do to the past problems with bad Bearings. If the original problem was a bad set of rod bearings causing enough clearance issues to cause the pistons to contact the bottom of the cylinder heads?? Then that is what caused the piston failure the second time around. No offence but the first time you took it apart it should have had a new set of pistons and rings along with the resized rods and bearing's etc. I would Highly recommend a tear down and new set of pistons. Without a complete tear down you may have some extra debri floating aroung some where just waiting to take out your cam or a set of main/rod bearings. I would say that the original assemblers of the short block should have let you know of the possible potential for this to happen after reusing old parts. Not trying to offend just giving my opinion. Good luck and just think it could be worse :}

Wishmaster's87IROC

iTrader: (4)

The first problem was not a bad set of bearing....rememeber I got this motor off ebay. The oil pump was a big block pump that sat about 3 inches off the bottom of the pan. THat was the cause of the me spinning all my bearing and ruinning my crank. NO OIL!! Everything is NEW in the block now except for the pistons. The rods were all reconditons.. Yeah maybe from the piston smacking the head when the #7 bearing went completely out it eventully weakened the piston and it finally gave out....but the shy ring gap and MAINLY detonation caused this ...Im sure!.....well I hope...LOL
Yeah the engine builder did sugggest when I had it rebuilt to put in new pistons but I said use what I got...they should be fine. ...and Im sure they still are....again I hope!...I dont have the $$$$$$$ for new ones.

gofast51

You also have to remember that KB pistons require more ring end gap than other pistons. They specify on there website what that should be. If the people who put together the lower end didn't know this and they were too tight it would tear the top ring land. Could have been the cause of the spun bearings...pistons too tight in the bores when the ring gaps closed when the motor got hot.

Orr89RocZ

iTrader: (20)

gosh your havign all kinds of good luck with this combo

thats crazy man!

Wishmaster's87IROC

iTrader: (4)

You aint kidding!!!!!!!!!
when I get it back together this time...Im not even going to fire it up.
People will ask me about my car and I'll just say yeah its done. No NO NO...dont fire it up..but its done though...LOL

Damon

I'll tell you exactly what happened, but first let me show you my credentials on this matter:



I have 3 sets of KB pistons that I've done that to.

Wishmaster's87IROC

iTrader: (4)

wow! and the reason was?

Damon

Now that we have that out of the way, I'll let you know exactly what happened in that .01 second when your piston went bye-bye....

The main problem is not what is obvious to the eye- that is the RESULT of what caused the problem. The piston didn't magically "shatter" like glass or "vaporize" from detonation. What killed it, ultimately, is too much heat in the combustion area, often combined with too small a ring gap. Heat is most often due to detonation which spikes combustion temps and pressures to the moon. But running too lean and/or with too much spark advance can do it too. However, too lean and too much spark advance usually go along with detonation hand-in-hand so you get quickly to the same end result.

What that excessive heat does is that it gets the top ring too hot and the gap starts to close down. When it reaches ZERO end gap it "locks" in the bore when the piston reaches TDC. As the piston starts to descend the ring doesn't want to come down with it any more, but the spinning crank has plenty of power to force it to come down. As it does so chunks of the top ringland are forcibly ripped off the piston by the top ring. That's the missing material from your piston face.

Then a couple things happen. First off, you can imagine that a ring locked tightly in it's bore is none too kind to the bore itself. It "scrapes" down the bore and leaves those vertical scratches down the bore. Mystery #1 solved.

The chunks (not aluminum "vapor" or "powder"- aluminum CHUNKS of various sizes) that get ripped off the piston then fly around in the combustion area above the piston. They sometimes are small enough that they blow right out the exhaust doing little or no further damage. But often they get a little mashed up before they exit. This can result in bent spark plug side electrodes, aluminum chunks mashed into the cylinder head and piston face, carnage to the valves and valve seats from debris getting caught between the valve and it's seat as it closes, etc.

Oh.... and my personal favorite.... when a really nice chunk gets caught near the rim of the piston in a "quench" area with the head. On the next up-stroke- OUCH! Imagine what it's like if the piston trys to crush a nice chunk of aluminum in a tight space. It obviously can't crush it withou a LOT of pressure. That pressure causes the piston to rock VIOLENTLY in it's bore. When it does so 2 things can happen. #1 is that the piston can literally crack the bore down it's length vertically or blow whole chunks of it away- major carange, but not guaranteed to happen. But #2 is one that almost always happens...... the violent rocking of the piston in it's bore causes the piston skirts to collapse slightly and become "barrel shaped." It can also crush the ring land down on the ring so that you can't remove it from the piston. Sound familiar? Mystery #2 solved.

Now for the $64,000 question..... why does this seem to happen to hypereutectic pistons? Are they weak? ABSOLUTELY NOT! They are every bit as strong as most forged pistons. However, they have one major difference that you can't see with your eye- they don't conduct heat as quickly as a forged piston. When forged pistons get a lot of heat thrown at them they QUICKLY conduct that heat away down into the skirts and underside of the piston where the oil can carry it away. Hyper pistons can't get the heat away as quickly and so they are much more likely to overheat the top ring, causing all the above problems. KB Hypers are particularly susceptible to this becuase they put the top ring even closer to the piston face than most other designs. It's a double-whammy. And it's also why KB Hypers call for such huge top ring gaps, even in N/A applications.

NO pistons will survive forever in a detonation environment, it's just that certain pistons will survive longer than others by virtue of their materials and design.
----------
Oh. and here's another pic I just found showing the same type of damage but worse. This one blew up bad enough I had to have the combustion chamber on that cylinder welded up and ground back down to shape again......

Wishmaster's87IROC

iTrader: (4)

excellent explantion! That is what others have told me all rolled into one. I can say that it was probably 75% or more my fault for driving it will to much timing and having it detonate and when I finally fixed it the damage was already done. As far as the builder I give them the other 25% for not gapping it to the correct gap. THey dont mess with KB pistons and Im sure they ASSumed that they were to be set up like regular pistons. I do remember telling them to gap my top rings to .032 but I guess they forgot. They were at .024 which KB calls for .026 MINIMUM on a N/A engine. I will be running nitrous when I ever get this motor running right so the gap is bore times .0080which comes out to .3232 MINIMUM I will gap them to .033 to play it safe.

Guest

If you keep the KB's, run more gap than that. Its not going to use oil.

Wishmaster's87IROC

iTrader: (4)

Yeah Im keeping the pistons I have, I dont have the extra cash to buy an whole new set. Ive already ordered the replacement piston that matches the correct weight of the pistons I have when I had the crank balanced. Ive also ordered my plamsa moly rings for just that one piston.
You say gap them more than .033? what should I gap them to? what do you say I should gap the second ring to? or does it matter? KB says it doesnt mattter.

Guest

Second ring doesnt matter. I'd gap the top at .036 if you plan to spray it. Better safe than sorry. You see what sorry does. I'm not so sure that was caused by the previous mess. Maybe... but doesnt look like it to me.

Wishmaster's87IROC

iTrader: (4)

nah Ive never hit he button yet. Im pretty sure it was detonation and the smaller ring gap that was on them. So yeah, I'll do the .036
.032 is the bare minimum so more should put me in the safe zone.

InfernalVortex

iTrader: (4)

Out of curiosity, how does one measure ring gap?

jtrescot

Using caution not to scratch the bore, you put the ring in the cylinder. When the ring is squared up in the bore you measure it with feeler gages.

Wishmaster's87IROC

iTrader: (4)

yeah, thats what I do. You take the top or second ring off the piston and stick it down in the matching cylinder and then I use the end of the piston to square it in the hole and down about an inch. Then I take my feeler gauge and measure in between the ends and pull it back out and gap it to whatever gap I need. I make sure they are all the same. Watch out when take off or putting on the rings to the piston they have to kinda spiral off/on the piston

sofakingdom

iTrader: (1)

NO!!!! NOT the compression rings!!

Only the oil rings do that. The compression rings, you use a ring expander, which is kind of like pliers in reverse. The tolerance between the side of the rings and the piston is VERY tight; you do not want any variation in the ring thickness like a twist, or ANY damage, not even a scratch, however slight, to the piston ring lands. You MUST expand them STRAIGHT, drop them down over the ring lands, and release the expander so that they slip gently into place with NO force. If your compression rings have been "spiralled" on or off, then you probably need all 8 new pistons, because the ring lands of all of them are probably all chewed up.

Likewise, when you gap the ends, you MUST make sure that there are no microscopic burrs or ships in the ends of the rings. Those will scratch the pistons and the bores, and cause them not to seal.

Rings are really a precision part, and require great care to get them right, for really "premium" operation of an engine. Sure, Cletus and Billy Bob can slap one together out behind that old barn in the back 40 in less than an hour, and it'll "run"; maybe even "run good" (as people will no doubt step up and tell you, "I did it that way and mine works fine"); but not as good as it could. What they don't, and can't know, is that if someone else built the same motor with a little more finesse, it would BEAT theirs, EVERY TIME. Attention to details like that is part of the reason why your typical builder can take the same parts as those guys that win the Engine Masters competitions and such as that, and not get NEAR the same power out of the IDENTICAL SAME parts list. It's in the details.