Broke connecting rod?
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Re: Broke connecting rod?
From the pics I don't see anything that would indicate the rod was under stress before it broke,no heat, no bearing damage, no crank journal finish issues so I am guessing either just a rod beam failure unless the issue created was a valve part breakage in the chamber prior to rod failure.
Did the other two rod failures occur with the same results? Has anyone magged or Xray'd the 7 remaining rods? What rpms on runs? Any other changes to the engines that had same failures after freshening? Can you get the pin out for pics?
Did the other two rod failures occur with the same results? Has anyone magged or Xray'd the 7 remaining rods? What rpms on runs? Any other changes to the engines that had same failures after freshening? Can you get the pin out for pics?
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Re: Broke connecting rod?
Both valves were bent but not broke. no piston to valve issues with other cylindersengineczar wrote: ↑Tue Sep 18, 2018 8:22 am Were both valves in that cylinder still intact even if bent?
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Re: Broke connecting rod?
One previous engine did not have a broke rod. It had the main webbing broke out of it. It was an aftermarket race block. The crank in it had a crack in it also.Newold1 wrote: ↑Tue Sep 18, 2018 8:45 am From the pics I don't see anything that would indicate the rod was under stress before it broke,no heat, no bearing damage, no crank journal finish issues so I am guessing either just a rod beam failure unless the issue created was a valve part breakage in the chamber prior to rod failure.
Did the other two rod failures occur with the same results? Has anyone magged or Xray'd the 7 remaining rods? What rpms on runs? Any other changes to the engines that had same failures after freshening? Can you get the pin out for pics?
2nd engine had a rod break. I have not seen this engine.
3rd engine was all new parts and has a broken rod.
I have not pulled the other rods out of this engine yet.
Max rpm was 7200. I wanted him to run it to 7600-7700 but he didn't want to break it!
I will get pin out this evening and get pics.
Re: Broke connecting rod?
With the seats looking so good (and the valves?), the piston and chamber divots appear to be F.O.D. More shots of the rod could help clarify (in the first, it looks folded/twisted), but it appears it may have buckled due to the piston being locked by the stray object. Call it 'mechanicalling' vs. 'hydraulicing'.
There's no way an F.O. could get past the piston from below so it must have been inhaled through the port; the damage just can't be coincidental with the broken rod.
There's no way an F.O. could get past the piston from below so it must have been inhaled through the port; the damage just can't be coincidental with the broken rod.
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Re: Broke connecting rod?
With the damage to the head showing a curvature or an arc, could this be from pieces of the top ring? Any indication at all of detonation when you examine the other holes?
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Re: Broke connecting rod?
So if both valves were intact ( just bent) in that chamber and looking at the top of the piston I would say something entered the chamber. Lots of impact damage on the quench pads and around the peak of the dome.lance flake wrote: ↑Tue Sep 18, 2018 8:54 amBoth valves were bent but not broke. no piston to valve issues with other cylindersengineczar wrote: ↑Tue Sep 18, 2018 8:22 am Were both valves in that cylinder still intact even if bent?
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Re: Broke connecting rod?
That damage on the dome is from piston turning when rod broke that is also what bent the valves
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Re: Broke connecting rod?
seems to me its something related to how he is driving it. Like is he hitting a rev limiter, how it comes off the transbrake, how he does his burnouts or shifts gears. I don't know how or what but if all these failures to the same guy on 3 different motors ?? What parts have been the same through all builds ? Just the intake and top end ??
Brian
Brian
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Re: Broke connecting rod?
I am seriously thinking something with ignition may be causing these concerns
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Re: Broke connecting rod?
Whatever hit the piston came through the intake. Rings were perfect could reuse them! lol.Tom Walker wrote: ↑Tue Sep 18, 2018 9:47 am With the damage to the head showing a curvature or an arc, could this be from pieces of the top ring? Any indication at all of detonation when you examine the other holes?
I can't imagine the small dings in the piston and quench part of the head could cause the rod to break. I have seen complete valve heads break off and beat around with the rod being reuseable!
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Re: Broke connecting rod?
He is a smooth driver no banging the rev limiter. This is a footbrake deal. I am 99% sure he has a electric shifter with a 7200 chip in it. I think he has a 7800 high side chip in it.prairiehotrodder wrote: ↑Tue Sep 18, 2018 10:37 am seems to me its something related to how he is driving it. Like is he hitting a rev limiter, how it comes off the transbrake, how he does his burnouts or shifts gears. I don't know how or what but if all these failures to the same guy on 3 different motors ?? What parts have been the same through all builds ? Just the intake and top end ??
Brian
The intake, hat, complete fuel system, complete ignition system, and ati balance was reused. This engine was new from valve covers to oil pan including flexplate
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Re: Broke connecting rod?
Does it look like the rod stretched before it broke ? Like the crank was trying to pull it down but it didn't want to come down ?
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