KZScott
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posted October 30, 2011 05:15 AM
rod bolt stretch
How much stretch should I be looking for on stock 12 rod bolts? Ive always done it as per the manual and TQ to 16 ft lb then go another 120 degrees. its my understanding that measuring stretch is the better way to do it.
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01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
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Bigbore4
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posted October 30, 2011 06:10 AM
I think it's about .005. If it takes less torque and rotation to get that, the bolts junk.
I thinks that's correct, but I also thought I was wrong once and was mistaken 
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KZScott
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posted October 30, 2011 11:43 AM
I was thinking it should be around .005 or .006 looking at Carrillo specs
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01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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Bigbore4
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posted October 30, 2011 01:52 PM
Using the stretch method checks the elasticity of the bolt. If it takes less torque, the bolts obviously rubbish.
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dougmeyer
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posted October 30, 2011 06:20 PM
Don't use the Carillo spec (or any other bolt) as a guide. A given bolt design,length, material, etc. will be different from another, and especially different from the studs on the stock rods. Follow the book.
Doug
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Shane661
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posted October 30, 2011 06:51 PM
 Edited By: Shane661 on 31 Oct 2011 02:52
quote:
How much stretch should I be looking for on stock 12 rod bolts? Ive always done it as per the manual and TQ to 16 ft lb then go another 120 degrees. its my understanding that measuring stretch is the better way to do it.
Scott, since you have 8 bolts to do...and there is no stretch spec...
Why not check stretch on 8 new bolts while doing it to factory spec. They should all be about the same, and give you an idea of what to look for. Or you could just use a spare rod and do a few sets of bolts, without worry about resziing the rod.
Just a thought...
Shane
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KZScott
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posted October 30, 2011 07:34 PM
quote:
Don't use the Carillo spec (or any other bolt) as a guide. A given bolt design,length, material, etc. will be different from another, and especially different from the studs on the stock rods. Follow the book.
Doug
thanks Doug, ill keep doing it the way I have been. btw Muzzys found a new set allready bushed Im getting 
quote:
Scott, since you have 8 bolts to do...and there is no stretch spec...
Why not check stretch on 8 new bolts while doing it to factory spec. They should all be about the same, and give you an idea of what to look for. Or you could just use a spare rod and do a few sets of bolts, without worry about resziing the rod.
Just a thought...
Shane
why did i have to read this at 1230 am? i have rods I could practise on after i make something to hold my DI... not sleeping again tonight....  lol
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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tcchin
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posted October 30, 2011 09:40 PM
You will need to use a beam-type torque wrench, and measure applied torque, angular displacement and stretch in order to get enough information to improve upon the stock method. As Bigbore4 implied, just measuring stretch at a given angular displacement is not sufficient. You need to measure applied torque too, in order to determine if your bolts are necking or otherwise failing. Just be sure you are consistent with the assembly lube on each bolt, as torque is very sensitive to that.
Note that I had a batch of bad bolts from Carrillo that were internally flawed such that they lost modulus each time they were torqued. They always came back to the original length, but they just kept getting softer and softer. I've never seen anything like that before. Right before I gave up on them, they were stretching .0055" at 20 lb-ft. Yowza!
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KZScott
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posted October 31, 2011 06:46 PM
Thank you Tim, Ill be doing it by the fsm. someday ill try it that way....
Ive been using 10 40 mineral oil as the lube for rod bolts/nuts(book says motor oil). switching to something like ARP ultra torque would throw off the amount of stretch obtained(more?) if doing it by the book correct?
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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tcchin
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posted October 31, 2011 08:58 PM
I read a test where motor oil was compared with a moly-fortified EP grease like Dow Corning BR2 Plus, and the grease reduced required torque at stretch by something huge, like 40%. This corresponds well with the results published in the Loctite 51609 TDS that compared the coefficient of friction between solvent-cleaned bolts and 51609-treated bolts (.27 vs .16 or ~41% reduction). BTW, Carrillo uses Loctite 51609 to develop all of their torque specs. Needless to say, if the same torque were applied to both sets of bolts, the one treated with Loctite 51609 would show way more stretch, may have way more preload and may even fail from over-tightening.
So even switching from motor oil to assembly lube, like Redline or Royal Purple, would affect torque-at-stretch values considerably. This is probably why the OEM's specify an angular displacement preload method instead of a torque-only method. Angular displacement preloading yields very accurate results regardless of applied torque, as long as the bolt is within design specs (cross-sectional area and modulus of elasticity).
Don't rule out measuring applied torque when using the FSM method, though. That measurement is a good sanity check of the bolt's integrity.
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dougmeyer
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posted November 01, 2011 08:27 PM
NEVER use moly grease on bolt threads or nuts, regular motor oil only. It is acceptable to use a dab of moly on the seating surface of the bolt head/washer to preclude galling. Like Tim says, the torque change is substantial. I worked on a comprehensive rod bolt test once, screwing the bolts into a fixture and measuring stretch vs torque and it was a real eye opener.
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KZScott
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posted November 05, 2011 04:26 AM
thanks guys! I knew I could get the best info from you
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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entropy
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posted November 05, 2011 10:10 AM
quote:
NEVER use moly grease on bolt threads or nuts, regular motor oil only. It is acceptable to use a dab of moly on the seating surface of the bolt head/washer to preclude galling. Like Tim says, the torque change is substantial. I worked on a comprehensive rod bolt test once, screwing the bolts into a fixture and measuring stretch vs torque and it was a real eye opener.
I'm guessing Doug is talking about stock rods.
For Carrillos;
"The CARRILLO connecting rod is a precision, high strength, quality connecting rod, which when properly installed and maintained, will perform
flawlessly in today’s racing and high performance internal combustion engines. We would like to offer some suggestions and specifications that
should be helpful in your installation.
BOLTS
All bolts should be lubricated under the heads as well as on the threads. We recommend the bolt lube included, or as an alternative, molybdenum
base paste mixed with engine oil.
Crower
The Ti rods in my Busas require a special lube for Ti.
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Y2KZX12R
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posted November 06, 2011 12:06 PM
+1
Always use the lube that the manufacturer or manual tell you to use. It does have big impact on bolt stretch for a given rotating torque.
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Y2KZX12R
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dougmeyer
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posted November 06, 2011 07:36 PM
I wasn't referring to stock rods, because stock rods of most types use nuts not bolts. Big difference because of the amount of thread engagement..
You would find that the moly / oil mix would have a different stretch/torque than straight moly. The greatest danger is if the stretch spec is set with oil and then you use moly. If the stretch is set with moly, or a proprietary lube, you need to use that.
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tcchin
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posted November 07, 2011 04:13 PM
Hey Doug. When you say, "The greatest danger is if the stretch spec is set with oil and then you use moly," do you mean that there's danger even if the same stretch spec is achieved upon installation with either oil or moly, or were you referring to installation using just the torque value (without regard for stretch) leading to dangerous levels of preload in the bolt?
As I understand it, the only critical numbers are bolt stretch primarily, and secondarily a minimum torque value to assure bolt integrity.
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Y2KZX12R
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posted November 09, 2011 05:41 PM
Good point Doug.
quote:
As I understand it, the only critical numbers are bolt stretch primarily, and secondarily a minimum torque value to assure bolt integrity.
Yea I've seen bolts go soft.
Tim, also its good to keep track of each rod bolt free length and document it for future reference. If you get a bolt that doesn't comeback to with in .001" each time its cycled then toss it.
When the bolts go soft like that they dont come back to length.
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