Y2KZX12R
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posted October 26, 2010 07:07 PM
Final Conclusions Reached on Loring Motor
Well after a lot of post mortem analysis and sending out parts for testing and evaluation etc. we have reached a final conclusion as to what happened to the zx14 engine at Loring this year.
The bottom line is the rod bolts didn't have enough stretch.
Here's why......
Carrillo switched to another bolt manufacturer a year or so ago. Some of you may have noticed that the torque values for the DNE (do not exceed) torque went down on most of the rod bolts at that time.
It wasn't clear at that time as to why. They switched over from 5/16" bolts to the 8mm bolts and the torque went from a DNE of 45 ft lbs to a DNE of 30 ft lbs. but the difference is only .002" in dia. not a big difference.
During assembly I noticed that the bolts didn't stretch enough on the first cycle. Not a big deal because this is fairly normal especially for an L-19 bolt. We even used the supplied anti seize provided with the rods.
Well I had to cycle the bolts 4-5 times to get to the minimum recommended stretch of .0045-.006". They just stretched barely stretched to .0045" the 5th time at the DNE of 30 ft lbs. I took it as the threads were burnishing in.
On inspection of the damaged rod we noticed that there was evidence of the rod caps moving. There was metal to metal transfer where the cap mates to the rod. This is evidence of inadequate clamping force of the rod bolts. So naturally we suspected a problem with the rod bolts them selves. After doing some return rate stretch tests and talking to the bolt manufacturer A1 we cane to the final conclusion that Carrillo is way off on there published DNE torque specs. You will find this data sheet on there web site.
http://www.cp-carrillo.com/LinkClick.aspx?fileticket=rGOOtq6Rn%2fY%3d&tabid=76
The fact of the matter is that you need between 41 and 43 ft lbs to get the proper stretch on the first cycle with the supplied lube. The DNE torque should be 45 ft lbs not 30.
Now on most motors like for drag racing this problem of inadequate bolt stretch/torque may never rear its ugly head. However, on a +5mm stroker engine that was reving well over 11,000 rpm for 7 passes that last 26 seconds a pass that's not good.
That's about 2 minutes and 41 seconds total at over 11,000 rpms. Mind you that this engine was making more naturally aspirated hp than any other zx14 anywhere at 248 hp.
We have done a few more of these head and cam packages sense then but this was the first.
So here's a warning to everyone who is using Carrillo rods with the 8mm CARR rod bolts with the SM8 head marking. DISREGUARD THE DNE TORQUE SPEC!!! The DNE should really be 45 ft lbs!!!! You will typically need 41-43 ft lbs to get to .0055"- .006" stretch. Dont run these bolts with .0045" of stretch!!!
I have notified Carrillo of the errors in there torque spec sheet.
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Shane661
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posted October 26, 2010 08:01 PM
Very good info. 
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ZRXDean
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posted October 26, 2010 08:30 PM
Wow, I'm surprised that Carrillo would make such a serious mistake. Thanks for reporting all this hard-gained info, you are a real asset to the community. So the fuel switch was just a coincidence, great detective work.
thanks Jim 
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Shane661
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posted October 26, 2010 08:35 PM
 Edited By: Shane661 on 27 Oct 2010 04:37
quote:
Wow, I'm surprised that Carrillo would make such a serious mistake. Thanks for reporting all this hard-gained info, you are a real asset to the community. So the fuel switch was just a coincidence, great detective work.
thanks Jim
Dean, the change in bolt manufacturers was also likely "hard-gained" from what I can tell...ask me about it at Maxton. 
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whitehendrix
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posted October 26, 2010 11:10 PM
MAN. that sucks, Jim. sorry you had to have a failure to see this.
great info tho.
so they simply retained the same elastic point and DNE spec as before but amended the spec in the technical sheet?
were those meant to be plastic-region torqued instead of elastic, possibly?
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entropy
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posted October 26, 2010 11:15 PM
excellent info Jim, thanks a million!
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aliveagain
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posted October 27, 2010 01:57 AM
I guess we have more then one professor on the board. 
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Y2KZX12R
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posted October 27, 2010 04:12 AM
quote:
Wow, I'm surprised that Carrillo would make such a serious mistake. Thanks for reporting all this hard-gained info, you are a real asset to the community. So the fuel switch was just a coincidence, great detective work.
thanks Jim
Dean,
So were we.
Yes the fuel switch was just coincidence. Or possibly the engine did make more power with the fuel and allowed it to pull a higher rpm which stressed the rod bolts even more allowing the rod caps to walk all over the place even worse. But it wasn't the fuels fault.
Pre-teardown I thought it was the lower octane fuel because I saw the hammered bearing and thought it was from detonation. It was my mistake for jumping to a conclusion before having all the facts in front of me.
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Y2KZX12R
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posted October 27, 2010 04:13 AM
quote:
quote:
Wow, I'm surprised that Carrillo would make such a serious mistake. Thanks for reporting all this hard-gained info, you are a real asset to the community. So the fuel switch was just a coincidence, great detective work.
thanks Jim
Dean, the change in bolt manufacturers was also likely "hard-gained" from what I can tell...ask me about it at Maxton.
LOL
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Y2KZX12R
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posted October 27, 2010 04:28 AM
Edited By: Y2KZX12R on 27 Oct 2010 12:34
quote:
MAN. that sucks, Jim. sorry you had to have a failure to see this.
great info tho.
so they simply retained the same elastic point and DNE spec as before but amended the spec in the technical sheet?
were those meant to be plastic-region torqued instead of elastic, possibly?
Well its funny, they don't publish a "torque to" spec and never have. Just a DNE spec.
So they are expecting people to do it the proper way and use a stretch gauge.
I've talked to many people that think the published DNE spec is a "torque to" spec.
If you were to assemble the engine and torque these bolts to 30 ft lbs once it would be very scary with .001"-.0012" of stretch on the bolts. I know of at least 4 instances where this has happened and resulted in catastrophic rod failure.
As a side note that i should have mentioned in the first post. As you cycle these bolts, as in most any bolt, it will take less and less torque to reach the desired stretch with each cycle.
You NEVER want to simply use the same torque reading each cycle without monitoring stretch. If you ever go over the MAX stretch spec of .006" then throw the bolt out and get a new one. also its a good idea to document the free standing length of the bolt when they are unloaded for the first time, as in the first time you remove the bolts from the rod when new. Save this info to compare to for each time you unload the bolts. The bolts should come back to the original unloaded length.
You will need to use two small ball bearings on each end of the bolt and use a dial caliper for this. The stretch gauge doesn't measure actual length, its just a comparator.
Also wash your hands well with soap and water and then coat your hands with wd40 or some kind of oil before handling the bolts. Many of these alloys suffer from whats called hydrogen embrittlement and it weakens the bolts over time. Its caused by the salts in your sweat.
I suppose I should have mentioned that as well.
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ZRXDean
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posted October 27, 2010 07:06 AM
Wow, I need to be a little more careful in how I slap these motors together!
Thanks again Jim
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Y2KZX12R
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posted October 27, 2010 09:20 AM
Edited By: Y2KZX12R on 27 Oct 2010 17:22
I just received an official response from CP/Carrillo....
They are doing the right thing and they are going to provide a new rod and 6 new bolts and REVISE THE TORQUE SPEC SHEET so this doesn't ever happen again.
This speaks volumes about CP/Carrillo and their ability to correct a problem and move on.
This will benefit everyone in the long run.
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ZRXDean
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posted October 27, 2010 09:28 AM
Good for them. Did the other 3 rods show signs of cap movement, and will this be an issue once the new bolts are in place? Basically, I'm asking if they should have replaced all 4 rods.
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Y2KZX12R
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posted October 27, 2010 12:47 PM
Dean one of the other rods showed some slight signs of cap movement but no metal transfer. The rods them selves are fine. Actually the bolts dont really need replacing either but were doing it for good measure.
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2000redrocket
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posted October 27, 2010 02:14 PM
jim funny you mention about total streach on the bolt over time.
in the navy in the yards in boston i was on the QA team and had to be there for all out high pressure air flask pressure tests to mesure stretch.. i asked what it started out at volume wise cause we had it in fluid and as it expanded it pushed fluid out.
it was in a one time mesurement. i can imagin it could of been just getting bigger over the typical 20 years of navy ship life or more.
we went to 3000psi on the ship. the test was at 5000psi. we all were wondering what it was going to do if it failed. but the navy has been around a long time so i guess it is all good or it would of been changed.
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tcchin
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posted October 27, 2010 05:39 PM
Edited By: tcchin on 28 Oct 2010 01:42
quote:
I just received an official response from CP/Carrillo....
They are doing the right thing and they are going to provide a new rod and 6 new bolts and REVISE THE TORQUE SPEC SHEET so this doesn't ever happen again.
This speaks volumes about CP/Carrillo and their ability to correct a problem and move on.
This will benefit everyone in the long run.
I thought I brought this issue up in February when I windowed my Jim Mondo Head motor due to a CARR SM8 rod bolt failure. The batch of bolts that were originally supplied with the rods stretched to .006" with 20 lb-ft of torque. I took these back to Carrillo and they exchanged them after they verified my test results. They advised me that the bolts they gave me should be torqued to 30 lb-ft, and this should result in .005" stretch. The motor was used in roadracing, where the motor spins near its redline most of the time for hours...or at least until the rod bolts fail.
CP/Carrillo examined my broken pieces and replaced by failed connecting rod at dealer cost (thanks a lot), reconditioned the good rods and tested the remaining bolts for me. I was not happy with how all that turned out, considering I lost the rest of my motor. And after all this, their stated NTE torque spec was still 30 lb-ft. I think I'm going to go with .0055-.0060" stretch with a minimum of 30 lb-ft applied torque. If I can't get the stretch I'm looking for, I'm going to ask them to exchange the bolts.
As a side note, Carrillo promised me that they would include a minimum torque spec in their spec sheet to help identify the issue I had with my original bolts, but they never did. We'll see if they take it seriously this time.
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whitehendrix
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posted October 27, 2010 05:47 PM
great that they taking care of you for this.
i like your trick with the caliper and BBs, btw.
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
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Y2KZX12R
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posted October 27, 2010 06:35 PM
Tim I do remember you having those issues. In fact Ryan and myself talked to Cindy, Stefan, and RC at the booth at the Indy dealer show in Feb and asked them if they were having rod bolt issues and they said they were not. ???
So your first bolts were soft and stretched too much...? Or maybe they were the weaker bolts mismarked?
A min max torque spec would be nice.
Ryan had a hard time getting to the proper stretch range on one of his busa motors as well.
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tcchin
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posted October 28, 2010 10:36 AM
quote:
Tim I do remember you having those issues. In fact Ryan and myself talked to Cindy, Stefan, and RC at the booth at the Indy dealer show in Feb and asked them if they were having rod bolt issues and they said they were not. ???
So your first bolts were soft and stretched too much...? Or maybe they were the weaker bolts mismarked?
A min max torque spec would be nice.
Ryan had a hard time getting to the proper stretch range on one of his busa motors as well.
Right, you guys went to the Indy show and freaked out the Carrillo guys with the long arm of the Dragbike Zone forum! That was funny.
I suspect that the alloy has some consistency (phase?) problems. Dimensionally, the bolts were fine, but the modulus was wrong, which is difficult to do with steel alloys. The bolts were perfectly elastic (no plastic deformation), but they stretched too much under load. Weird.
If 30 is the NTE torque value, I wonder what the minimum torque value is...
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knecum
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posted October 29, 2010 05:05 PM
I just got a set of A beams for a buse and the spec card says 20 ft lbs for the bolts. I assemble by bolt stretch but damn that seems like a low value... Good info Jim..
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Y2KZX12R
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posted October 30, 2010 05:24 AM
Steve, i compared the old sheet to the new sheet from Carrillo and many of the bolts have a lowered, much lowered MAX torque value.
Until they re-release all the new proper DNE torque values I'd torque them until you get to the upper 1/3 of the stretch range.
I don't know how long it will be before the new sheet is released but 20 ft lbs on a busa rod bolt is just plain scary.
I was talking to Ryan O and he is going to split his cases on one of the busas and re-torque his rods as well. One of his motors had the old rods/bolts and one has the new ones. And he is concerned with not having enough stretch on the new ones with the DNE at 30 ft lbs.
I think he got luckey.
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