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Greg, what is the advantage of the pistons you selected vs the JEs in my car? yours look like they are open , like the stock 968 piston, where mine are skirted on the wrist pin side. . also,what kind of oil control ring did you use? this was your first attempt at using a nicasil 928 block wasnt it?...
i know even Todd had an engine grenade with a non optimal oil control ring that failed after only1000 miles. it took him a long time to find the right ring. what did you use that was compatible to the Nicasil block?
could the piston have failed?
In that picture of the 968 pistons above, which are the optimal pistons.. the mahle or the KS? (it looks like the mahle has partial skirt and the KS is a full skrit.
I still think that detonation is not the reason.... if so, that bearing woudnt look so perfect.
what about rod to piston centering? even if it is off .065", the forces are huge on the rod vs centered. however, it looks like the break would be near the top vs near the bottom as where Mark's/Joe's broke.
Last edited by mark kibort; 05-22-2018 at 03:50 PM.
Greg, what is the advantage of the pistons you selected vs the JEs in my car? yours look like they are open , like the stock 968 piston, where mine are skirted on the wrist pin side. . also,what kind of oil control ring did you use? this was your first attempt at using a nicasil 928 block wasnt it?...
i know even Todd had an engine grenade with a non optimal oil control ring that failed after only1000 miles. it took him a long time to find the right ring. what did you use that was compatible to the Nicasil block?
could the piston have failed?
In that picture of the 968 pistons above, which are the optimal pistons.. the mahle or the KS? (it looks like the mahle has partial skirt and the KS is a full skrit.
I still think that detonation is not the reason.... if so, that bearing woudnt look so perfect.
what about rod to piston centering? even if it is off .065", the forces are huge on the rod vs centered. however, it looks like the break would be near the top vs near the bottom as where Mark's/Joe's broke.
Mark:
You just don't let up, do you?
I've built a whole bunch of Nicosil engines...so many I couldn't even begin to count them. I've used at least a dozen sets of these pistons. The correct ring package is super simple....it's been figured out for years....Nicosil is a super common cylinder treatment.
What you "think" isn't remotely relevant to what actually happened...you're 400 miles away....and didn't even build your own engine. It's literally like trying to have an intelligent conversation about parts in an engine with my pet dog....a complete waste of time.
I've shown you just about everything a beginning engine engineer would need....a spark plug that did everything but melt the electrode off.
Give it a rest.
I've built a whole bunch of Nicosil engines...so many I couldn't even begin to count them. I've used at least a dozen sets of these pistons. The correct ring package is super simple....it's been figured out for years....Nicosil is a super common cylinder treatment.
What you "think" isn't remotely relevant to what actually happened...you're 400 miles away....and didn't even build your own engine. It's literally like trying to have an intelligent conversation about parts in an engine with my pet dog....a complete waste of time.
I've shown you just about everything a beginning engine engineer would need....a spark plug that did everything but melt the electrode off.
Give it a rest.
Actually, i did build 5 of these engines that never had any issues. mine now, i didnt build. failure analysis is a process of elimination. I'm only looking at the common denominators, so dont get so defensive. we all are just interested in finding out the cause. If it is detonation, it will sure change my view of running 91 octane in mine, especially if i start making more power next season. (or do a shark-tune to bump things up)
So, you answered the one question. The reason i brought it up was that joes was his first that used Nicasil. ("nicosil"). I dont have near the experience that you do, but that rod bearing being perfect doesn't really scream that it had detonation that could break a rod. usually, most will say there should be some evidence of detonation on the rod bearing.
What about the rod not being centered. if it was off the amount in the graph, could that be a cause. (0.065")
you also used a new design crank in Mark and Joe's car this time around. could that be a possibility? I take it was your design and moldex built it to specs.
I agree that the rings should be simple. Todd spent a lot of time selecting the right ring, based on the nicasil bores. So, lets say you have had many cars that survived racing (not just street driving)
so, if it is detonation, which I'm sure that is entirely possible, maybe it was not enough to break a rod, but enough to break the piston top. it jams in the cylinder and then the rod breaks.
It just seems so odd that two engines, in cars that ran their prior engines with different cranks rods and pistons, lasted seemingly forever, but the new design, lasted in both, only a few race hours. these seem like the only changes same ecu, same intakes, same engine components on top of the short block....etc.
If you think Mark just ran the wrong fuel, or over reved it, as you said, it doesnt explain how his last engine lasted so long doing the exact same things and running the same RPM and fuel mixture
(1/2 - 91 and 1/2 -110 for an average of 100octane) a few things you are assuming he has done to cause the failure,and being there and seeing the video, I just dont see it.
these are just the questions that stand out to me.....maybe your "dog" has some different questions.
I guess we will find out soon enough when that piston is pulled out of the carcass,
Actually, i did build 5 of these engines that never had any issues. mine now, i didnt build. failure analysis is a process of elimination. I'm only looking at the common denominators, so dont get so defensive. we all are just interested in finding out the cause. If it is detonation, it will sure change my view of running 91 octane in mine, especially if i start making more power next season. (or do a shark-tune to bump things up)
So, you answered the one question. The reason i brought it up was that joes was his first that used Nicasil. ("nicosil"). I dont have near the experience that you do, but that rod bearing being perfect doesn't really scream that it had detonation that could break a rod. usually, most will say there should be some evidence of detonation on the rod bearing.
What about the rod not being centered. if it was off the amount in the graph, could that be a cause. (0.065")
you also used a new design crank in Mark and Joe's car this time around. could that be a possibility? I take it was your design and moldex built it to specs.
I agree that the rings should be simple. Todd spent a lot of time selecting the right ring, based on the nicasil bores. So, lets say you have had many cars that survived racing (not just street driving)
so, if it is detonation, which I'm sure that is entirely possible, maybe it was not enough to break a rod, but enough to break the piston top. it jams in the cylinder and then the rod breaks.
It just seems so odd that two engines, in cars that ran their prior engines with different cranks rods and pistons, lasted seemingly forever, but the new design, lasted in both, only a few race hours. these seem like the only changes same ecu, same intakes, same engine components on top of the short block....etc.
If you think Mark just ran the wrong fuel, or over reved it, as you said, it doesnt explain how his last engine lasted so long doing the exact same things and running the same RPM and fuel mixture
(1/2 - 91 and 1/2 -110 for an average of 100octane) a few things you are assuming he has done to cause the failure,and being there and seeing the video, I just dont see it.
these are just the questions that stand out to me.....maybe your "dog" has some different questions.
I guess we will find out soon enough when that piston is pulled out of the carcass,
Oh, there's a common denominator,, but I've been asked by Joseph to not comment.
Yeah, but he has done so many, you would think he would know how to spell it. i didnt Nikasil mine (personally, as greg mentioned) , so i have an excuse.. ...
Oh, there's a common denominator,, but I've been asked by Joseph to not comment.
Could the rod be off center? is that even a remote possibility? and if it was could that cause this kind of failure, or based on the graphics, cause it break up near the small end?
I think that one common denominator has been a factor in my car, once.. it seemed to survive a session ok.
Could the rod be off center? is that even a remote possibility? and if it was could that cause this kind of failure, or based on the graphics, cause it break up near the small end?
I think that one common denominator has been a factor in my car, once.. it seemed to survive a session ok.
Yeah, Carrillo started off with a clean set of paper, designed a rod specifically for the 928 engine, and didn't center it.
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
Yeah, Carrillo started off with a clean set of paper, designed a rod specifically for the 928 engine, and didn't center it.
Genius level stuff!
Again, looking for possible causes and what those effects could be. so if the rod, based on the journal size was custom to YOUR greg brown designed crank. is it possible the crank could have a tolerance of position that could cause an offset issue ? this maybe impossible, because you are perfect and designs of new components have never , in the history of engineering, ever ever had a mistake, but im just asking, IF it was a Devek designed crank (someone that cant defend themselves , lets say , and the crank allowed for some offset of say, the limit as shown by the graph, COULD that cause the crank to be over stressed or the piston to wear in the bore. its just a hypothetical question.
again, this is engineering 101 failure analysis methodology. it failed...........what changed........... I've identified several factors that did. new crank, new rods, (new pistons on joe's with nikasil block, but same pistons on Mark's using 968s) (and at some point , the change was made to go with chevy sized bearings, so the crank journals had to change size to keep alignment consistent) .
Now, you are being shifty and saying you know the factor that changed or the common denominator.. we all know where you are getting at.. BUT, if we assume you are right and detonation was the cause, you dont think its odd that the bearings show little signs of detonation? and if so, why would it caused a break at the big end? isnt it more likely the piston failed and the rod break was a result of that failure ? what caused the piston failure could be detonation, or alignment, correct?
Mark, it appears that you and Glen are the only ones on the entire planet who don't understand detonation and its devastating effect on an engine.
Go back and take a look at that spark plug, and do some Googling on reading spark plugs. That picture is worth a million words.
Hopefully then you'll understand that not even the most perfectly engineered 928-specific rod, and/or piston, both made/forged out of unobtanium, could withstand the withering, pounding, irresistible force called detonation.
The root-cause of the failure is NOT the rod, according to its spark plug. All other points are moot based upon the story told by the eye-witness at the scene, the spark plug.
Mark, it appears that you and Glen are the only ones on the entire planet who don't understand detonation and its devastating effect on an engine.
Go back and take a look at that spark plug, and do some Googling on reading spark plugs. That picture is worth a million words.
Hopefully then you'll understand that not even the most perfectly engineered 928-specific rod, and/or piston, both made/forged out of unobtanium, could withstand the withering, pounding, irresistible force called detonation.
The root-cause of the failure is NOT the rod, according to its spark plug. All other points are moot based upon the story told by the eye-witness at the scene, the spark plug.
I understand the force of detonation, but i also understand newtons 3rd as well.. if the force was so devastating, then why was it not shown on the bearings. generally we see evidence of this , and i dont think there is much. i know how to read spark plugs and yes, it looks like there are signs of pinging and high cylinder temps. i would love to see the other plugs as well. if it was just one plug, then maybe the intake had an issue. and maybe the detonation took out the piston .
Looking at all the evidence. did you see the piston? the wrist pin was pulled out of the piston. ive seen many broken rods where the piston still has a piece of the rod attached . couldnt the piston have failed first, due to detonation or otherwise, and then, pulled the wrist pin out of the piston, and then that could force the rod to break as it is forced up in the engine on the next stroke. then, the question is , what caused the piston to stop. do you not think that detonation can break a piston? if its broken, wont it stop in the bore , catastrophically? the next question i asked was if not detonation, could it be piston offset. (not blaming, but questioning if that is a possibility)
so, you are making an assumption that the rod was not at fault. i would agree, but the position of the rod on the piston could cause a failure as shown by the stress chart. assuming the offset is correct on the rod and the position on the crank is correct for a centered position, then the only other factors could be the piston and its components. agreed?? detonation can also cause rings to fail , and ring lands to break (piston failure)
but greg has made is very clear, that besides "driver error" in miss shifts, and lack of pre-revs for downshifts, that its likely detonation as the root cause. Just trying to narrow down the possibilities. thas why im asking if anyone has seen a piston fail due to offset issues.
look at the actual picture of the failure. how does the small end and wrist pin , break out of the piston, unless the rod is connected to the crank?
Here is a picture of the piston left in the cylinder on the no 8 cylinder that uses the same journal. its the same brand as my motor, JE, but if you notice, it doesnt have the full skirt perpendicular to the wrist pin as mine
does. Since this is a new design crank and piston to Joes motor than before when it seemingly lasted for ever. these are the major two variables that have changed. however, on marks blow engine, also failing in only a few hours, it used this design (968piston) , BUT, it used the newly designed crank and rod assembly, which is common of both engines that failed in short order. as i said, it seems impossible that the rod could have failed first, do to the piston wrist pin being broken out of the piston. this could only happen if the rod was connected to the crank...............then, it failed (broke in half) as it was pushed into the block in random angles.
so, the question is, "what caused the piston to stop in the block?" what was different vs the engines that lasted for many years and hours racing ?
Doesnt anyone see a potential problem with the above piston and rod position? do we have pics of the other pistons and rod positons. what about the spark plugs?
05-19-2018, 10:37 AM
