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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!
Greg, the rod is clearly not centered... so, if the rod offsets are correct, why is the rod not centered and if it isnt, why wouldnt this be a MAJOR problem? I dont think you need to be a "genius" to not see that the rod is not centered.
Here is a pic of my engine, where i just noticed how the rods look to be centered vs the rod positon in the failed engine. doesnt anyone see how this can be a possible issue?
Here is a pic of my engine, where i just noticed how the rods look to be centered vs the rod positon in the failed engine. doesnt anyone see how this can be a possible issue?
I'm rather confused myself now too.
I thought the rods in your motor were not centered, and the rods in the motor being discussed here were centered since those were the newly designed units to fix the un-centered problem.....
I'm rather confused myself now too.
I thought the rods in your motor were not centered, and the rods in the motor being discussed here were centered since those were the newly designed units to fix the un-centered problem.....
I thought it was accepted that the non-centering of the rod would be guranteed doom for the engine. all had the correct offset for a 928. i think i heard that devek might have had chevy offset rods with 928 bearings and sized big ends. im not sure though. the only thing that greg changed was the chevy bearing size , from what he said. (and going from an H rod to a tapered H rod)
i think i heard that devek might have had chevy offset rods with 928 bearings and sized big ends.
It's not a Chevy rod if it doesn't have SBC rod bearings. That kinda defeats the purpose.... yea didn't think that one all the way through
The most successful motor Mark Anderson ever campaigned had rods that were 100% to spec 928 except lighter & stronger units, still using 928 off the shelf rod bearings. Lasted how many years, how many races.....only blew when the intake failed.
So again, I go back to like page 3 - I cannot fathom why anyone is still building strokers with chevy parts when the stock bearings were proven to be reliable in the hardest driven 928 engine in history.....and in Todd's 1,000+hp twin turbo.
IMO Strokers built with Chevy rod bearings are done so to save $$$. You can order an "off the shelf" Chevy connecting rod for less money than having a 928 spec one designed and made.
Meanwhile....the guys building ***** out, ultimate engines around the small block Chevy are not even using Chevy sized rod bearings. They build engines around smaller diameter, wider bearings....
So why is the 928 world using Chevy parts when the Chevy guys don't?
By reducing the size of the rod journal, you can essentially reduce the friction created. That is why many racing cranks for the Chevy 350 use the 2-inch 327 journal size. This is possible because there are still plenty of rod options available. Nextel Cup teams use a 1.888-inch journal (commonly called a Honda journal) for an even greater reduction in friction.
I know if Todd could go back in time and re-design your motor from scratch, he would have used 928 rod bearings.
Originally Posted by 928sg
Kibort confused someone. Mission Complete~! Thread can be closed now.
Oh go away. If you were actually paying attention you'd see he's made some excellent points in this thread. He's limited to his own threads, yet you come in here to poke at him..... real classy.
It's clear you don't understand the gist of this discussion if that's all you have to say.
You raised an interesting point when you posted about his matter. My reading of the pic was that the offset was quite possibly more than the 65 thou needed to trash the engine in that finite element analysis diagram from Carillo. I was not sure where you got the photo from that you posted but from what I can now gather just for purposes of clarity, I understand you are saying that this is a photo from the Joe Fan engine that failed whilst Mark A was driving it - correct?
If so remember that engine has been through a major trauma. Whether it reflects the status pre-failure I have no idea.
Mark,
You raised an interesting point when you posted about his matter. My reading of the pic was that the offset was quite possibly more than the 65 thou needed to trash the engine in that finite element analysis diagram from Carillo. I was not sure where you got the photo from that you posted but from what I can now gather just for purposes of clarity, I understand you are saying that this is a photo from the Joe Fan engine that failed whilst Mark A was driving it - correct?If so remember that engine has been through a major trauma. Whether it reflects the status pre-failure I have no idea.
Fred,
YES, the picture was from Joe's engine that blew. the piston in the cylinder is the one exactly next to the one that failed. notice the offset issue. if the rods were correct, the crank journal position is wrong, the picture was taken with the broken rod still attached to the crank, so either the entire crank moved, or something else is off. I was saying that we see the piston with a rod that is off center, and that increases force on the rod and subsequently on the piston side. If the piston didnt stop in the cylinder wall due to detonation (broken ring land, or piston top failure) , then it was caused by the unbalanced force due to the apparent offset issue. One of the ways to determine if this was caused by post-failure stress/event, would be to see if all the other pistons left in the block, show the same offset issue.
one thing for sure (almost for sure) that piston wrist pin couldn't be pulled out of the piston, unless the rod was connected to the crank, So, the broken rod was post failure i would imagine.
I's not a Chevy rod if it doesn't have SBC rod bearings. That kinda defeats the purpose.... yea didn't think that one all the way through
The most successful motor Mark Anderson ever campaigned had rods that were 100% to spec 928 except lighter & stronger units, still using 928 off the shelf rod bearings. Lasted how many years, how many races.....only blew when the intake failed.
So again, I go back to like page 3 - I cannot fathom why anyone is still building strokers with chevy parts when the stock bearings were proven to be reliable in the hardest driven 928 engine in history.....and in Todd's 1,000+hp twin turbo.
IMO Strokers built with Chevy rod bearings are done so to save $$$. You can order an "off the shelf" Chevy connecting rod for less money than having a 928 spec one designed and made.
Meanwhile....the guys building ***** out, ultimate engines around the small block Chevy are not even using Chevy sized rod bearings. They build engines around smaller diameter, wider bearings....
So why is the 928 world using Chevy parts when the Chevy guys don't?
so, i guess the question is whether the 928 strokers from Devek used the corrillo rod using the chevy bearings and the wrong offsets, or whether they fixed it by making a 928 offset. (like Todd did for mine using the SBC bearings). the fact that mark and joe's motors with 928 sized bearings (custom offset corrillo) lasted so long would be proof enough for me that that was a good design. both lasted for many years of hard core racing. Then, some changes were made to the new engine design after failure, that used a different crank, different tapered H rods but same 968 pistons (968 copy pistons for Nikasil block with Joes). so why did both engines failed within only a few hours of racing? what are the possible variables that caused the failures? so far, i only see the crank and new rods as being the common denominator.
Fred,
YES, the picture was from Joe's engine that blew. the piston in the cylinder is the one exactly next to the one that failed. notice the offset issue. if the rods were correct, the crank journal position is wrong, the picture was taken with the broken rod still attached to the crank, so either the entire crank moved, or something else is off. I was saying that we see the piston with a rod that is off center, and that increases force on the rod and subsequently on the piston side. If the piston didnt stop in the cylinder wall due to detonation (broken ring land, or piston top failure) , then it was caused by the unbalanced force due to the apparent offset issue. One of the ways to determine if this was caused by post-failure stress/event, would be to see if all the other pistons left in the block, show the same offset issue.
one thing for sure (almost for sure) that piston wrist pin couldn't be pulled out of the piston, unless the rod was connected to the crank, So, the broken rod was post failure i would imagine.
so, i guess the question is whether the 928 strokers from Devek used the corrillo rod using the chevy bearings and the wrong offsets, or whether they fixed it by making a 928 offset. (like Todd did for mine using the SBC bearings). the fact that mark and joe's motors with 928 sized bearings (custom offset corrillo) lasted so long would be proof enough for me that that was a good design. both lasted for many years of hard core racing. Then, some changes were made to the new engine design after failure, that used a different crank, different tapered H rods but same 968 pistons (968 copy pistons for Nikasil block with Joes). so why did both engines failed within only a few hours of racing? what are the possible variables that caused the failures? so far, i only see the crank and new rods as being the common denominator.
One thing to wonder, I don't have my current stroker engine open or turned upside down so I can take a pic, but with a missing rod, for the damaged cylinder, could the other rod sharing the same rod journal slide offset and not full show the correct offset. I'm using a set of Oliver Ti rods that were blessed by devek for a build years ago and bought them uninstalled by Devek's customer. I also ran a set of standard SBC rods in my 1st stroker engine.
Thats what i would have thought as well, but NO......the picture was taken with the large end still attached, next to the rod still in one piece, and on the same journal . and as was reported, the rod bearings had NO signes of classic detonation marks.... it seems pretty clear that the piston stopped in the cylnder , for two possible reasons. the piston had too much side forces due to the offset of 60+ thou....and eventually wore into the cylnderwall and stopped. that forced the rod to pull the pin out of piston and then break itself in half as it was banging around without a piston. the other possibility, is that the piston was damaged by detonation that broke the piston top, or ring and caused the piston to stop as well . personally, i wouldnt think that misalignment would be that big of a deal, but thats intuition talking.. according to Corrillo and the stress graph, it sure shows some large increase in side forces that could have been a problem.. or the failure moved EVERYTHING around to create that offset.issue on the adjacent piston. all the other pistons would then NOT share this same offset problem if this is the case.. only pictures will tell when the motor gets more take apart.
I have a questions for you .. did the first devek strokers use the SBC rods and bearings? did they not have the right offset , or were they custom made? did they start with standard chevy rods and then change the offset for later gens. what greg the only guy that made 928 sized rods by corrillo so that they could used 928 standard bearings?
Originally Posted by 928sg
One thing to wonder, I don't have my current stroker engine open or turned upside down so I can take a pic, but with a missing rod, for the damaged cylinder, could the other rod sharing the same rod journal slide offset and not full show the correct offset. I'm using a set of Oliver Ti rods that were blessed by devek for a build years ago and bought them uninstalled by Devek's customer. I also ran a set of standard SBC rods in my 1st stroker engine.
There are a few classic signs of detonation damage. One is the metal sprayed on the plug. Another is that the ring lands were collapsed and mushroomed, seizing the top of the piston in the bore. But we won't know the answer until the heads come off and the top of the piston is visible. A typical failure mode for that leaves the top above the oil ring in the bore, with the rod and pin in the bottom of the piston.
Keep in mind that you are just doing a mental masturbation exercise. The answer will be a lot clearer when the heads come off and a full teardown and inspection is done. Waste no more time or bandwidth on this until Greg shares the inspection results.
Mark, you continuing to ignore the implications of the aluminum-infused spark plug would be the same as being genuinely-confused as to why your house burnt down when you observe that the entire plot of land is covered in 6-feet of flowing, molten lava.
Mark, you continuing to ignore the implications of the aluminum-infused spark plug would be the same as being genuinely-confused as to why your house burnt down when you observe that the entire plot of land is covered in 6-feet of flowing, molten lava.
thats not exactly true. i know the signs based on the spark plug appearance. usually, mild detonation will show these little ***** of aluminum way down in the insulation, so this is more obvious.... BUT, there are not the signs on the rod bearings to show the forces that could have destroyed the piston. thats the only inconsistancy i see on the the theory that detonation caused the piston failure. a better analogy about "your house burning down" would be finding a couple of cigarette butts melted in a couch and a shorted toaster. which is the cause?????? i guess we will find out. you cant deny that a offset issue posibley could be the cause.. after all that was talked about how it could be, and how "stupid" anyone would be to not use the proper offsett with the risks involved, why wouldnt it be a point of interest?
Originally Posted by dr bob
Mark--
There are a few classic signs of detonation damage. One is the metal sprayed on the plug. Another is that the ring lands were collapsed and mushroomed, seizing the top of the piston in the bore. But we won't know the answer until the heads come off and the top of the piston is visible. A typical failure mode for that leaves the top above the oil ring in the bore, with the rod and pin in the bottom of the piston.
Keep in mind that you are just doing a mental masturbation exercise. The answer will be a lot clearer when the heads come off and a full teardown and inspection is done. Waste no more time or bandwidth on this until Greg shares the inspection results.
agreed. we all know the effects of detonation on a piston, but in order for those forces to destroy one, you would think there would be the normal evidence on the rod bearings. I'm trying to understand your typical failure..... Ive heard the typical failure is what we see , would be the piston stopping and the rod splitting just below the narrow end with the crank journal's travel downward. youre right though. we wont know any of these answers until we see what the top of the pistons look like. however, it would be interesting to see the offset in the other cylinders to see if they show the same offset issue, or if that was caused by the failure itself. are you not curious about that? I'm certainly no expert at all regarding failure analysis of engines, but it seems to stand out as something that could be a possible cause.
05-30-2018, 01:46 PM
