Minimum Bearing Crush?

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steve cowan
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Re: Minimum Bearing Crush?

Post by steve cowan »

shoedoos wrote: Sat Jul 07, 2018 5:01 pm In the case where rod caps are aligned with dowels....how is the crush measured?
modok wrote: Sat Jul 07, 2018 5:25 pm The same. Why would a dowel make a difference? I don't really get it

just did a set of SCAT H-beams this week ARP 2000 bolt upgrade,resized
with new rod bolts i do a couple of stretch to spec cycles,in this case it is 0.006'' stretch which worked around 80 ft/lbs torque with ARP lube.
i remeasure the bigend with dialbore gauge the loosen rod bolts and check for zero stretch with stretch gauge,if bolt has not been over stretched (have not had that yet)
i fit bearings and stretch bolts again to spec and measure for bigend bearing clearances if they spec up ok in my case i want 2 thou i loosen bolts and torque to 20 ft/lbs on one bolt and measure with feeler gauge,i came up with 0.006''-0.007''
consistently on all rods,surely its safe to say if the cap does NOT spring up on the loose bolt side that you have no crush.
in my earlier post i checked the mains and the front and rear caps were easy to do but the the 4 bolt caps were a pain as they are registered tight in the block and Jay
(warp speed) pointed this out earlier as well.
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Re: Minimum Bearing Crush?

Post by jed »

Oliver has a new way of torquing there rod bolts. It uses the torque angle method followed by checking stretch.
If I could copy and paste, I would, but I can't so I didn't. Lol
But go to Oliver and downloads and u can find it.
They use the words "chasing the rod bolt stretch" the tension between the threads is so great above 50/60 lb
That u don't turn the bolt u just twist the bolt causing possible premature failure.
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Re: Minimum Bearing Crush?

Post by steve cowan »

hi Jed,
when i worked at GM Holden back in mid 80s -90s we used the torque angle deal on alot of 4 cylinder head bolts etc so am familiar with technique,
i believe that a fair amount of rod manufactures dont use stretch method on there rod bolts they use ft/lbs tension or newton metres for new age people,
back in 2000 i freshen up my BBC that i was running at the time and used a set of oliver steel rods,very nice,and i was not using the stretch method just tension ft/lbs deal,ran that engine for 5 years 8000rpm with a 300 shot with no apparent side effects,i started using the ARP spec rod bolt stretch method about 5-6 years ago on my stuff as from my research conrod failure is mainly caused by dirt behind the bearings and insufficient rod bolt clamping force,people may not agree but thats my opinion,i believe conrods fail very little from metallurgy issues.
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Re: Minimum Bearing Crush?

Post by shoedoos »

.....maybe I'll change my usage of the term dowel to that of the locating sleeves found on H-beam rods.....I would think they have the same tendancies as tight registers on a main cap?
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Re: Minimum Bearing Crush?

Post by modok »

Indeed it may slightly, yeah it could take 200 lbs of force or more to PULL that dowel, but in comparison to the force you can generate with a bolt that is still tiny. Bolt it together then loosen one side. It'll work.

I don't think you will have a problem with tight main caps, but WIDE caps will give trouble. Rod caps will have enough flex in the outside of the cap to allow one side to come together and the other to have a gap. But main caps may not, especially if they have a wide parting, and the parting surfaces are almost never PERFECTLY flat, unless you make them so and few do. With a wide parting even the slight deviations from flat on the surfaces make big differences in the size. It's touchy. In fact having FAR more surface contact than you need for the bolting force might actually be a source of trouble overall. If i proposed the parting surface should be reduced on many 'merican v8 with wide main caps, I'm sure many would cry heresy, but I think it might actually do good. One example that always stands out for me is the case/cummins 5.9 engine. It has main caps that are pretty much like rod caps......and they rarely walk or fret even though the bolts are TINY. Granted, they do have their limits.....but considering the application it's about the best I've seen. VS the dt466....which has far beefier main caps and more contact area but for what I've seen they ALL frett eventually. I think this is because the cummins cap can flex along with the crank to some degree, while it has SO much clamping force at the parting surface it never breaks that loose. I'm not sure if that's making any sense.....hard to explain. If you had a LARGE contact area at the parting and the cap flexs, maybe it lifts up one side a little. It rocks, and this rocking eventually leads to fretting. IMO if the bolting force and contact and flexibility of the cap are well matched, it should be impossible for it to fret.
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Re: Minimum Bearing Crush?

Post by shoedoos »

More from me, the reason I waded in on this crush discussion is I have a set of Probe H-beams that measure out on the big end bore diameter at 2.3259. I used a 545 Mitutoyo bore gauge to measure the big end.

I torqued the one side down to 40ftlb and the other side allows me to slide a .004 feeler gauge in to touch the cap locating sleeve.

I take it the measured crush will allow me to run the rod even though the big end housing bore is out of spec according to manufacturer tolerances?
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Re: Minimum Bearing Crush?

Post by modok »

Yeah, it's right on the minimum, but should be ok IMO. I believe it would.
But, it's so easy to re-size, why not re-size? If it's just one.
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Re: Minimum Bearing Crush?

Post by shoedoos »

I agree on a re-size being the correct way to do things, just looking for the cheat...and opinion on my line of thought....
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Re: Minimum Bearing Crush?

Post by Warp Speed »

shoedoos wrote: Sun Jul 08, 2018 8:17 pm More from me, the reason I waded in on this crush discussion is I have a set of Probe H-beams that measure out on the big end bore diameter at 2.3259. I used a 545 Mitutoyo bore gauge to measure the big end.

I torqued the one side down to 40ftlb and the other side allows me to slide a .004 feeler gauge in to touch the cap locating sleeve.

I take it the measured crush will allow me to run the rod even though the big end housing bore is out of spec according to manufacturer tolerances?
Have you tried measuring at a lighter torque, like 120in/lb? It may show a little more. 40lbs is allot. IMO
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Re: Minimum Bearing Crush?

Post by shoedoos »

I read the 120in/lb comment a few up and figured if I had .004 at 40ftlb then no doubt I will be fine at the lighter torque number.

I was more worried with the out of tolerance big end dimension.....what's the consensus on being a smidgeon outside the higher end of manufacturer's tolerance? Yes, the rods are used, and have been running as is....
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Re: Minimum Bearing Crush?

Post by af2 »

Now throw the fact the bearings have been run??????
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Re: Minimum Bearing Crush?

Post by shoedoos »

apologies, these are new H-series bearings I was using in the measurements.
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Re: Minimum Bearing Crush?

Post by af2 »

shoedoos wrote: Tue Jul 10, 2018 1:06 am apologies, these are new H-series bearings I was using in the measurements.
What I was asking is how much less crush would you see on a bearing that has been in use and still looks good?
GURU is only a name.
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Re: Minimum Bearing Crush?

Post by pamotorman »

af2 wrote: Tue Jul 10, 2018 11:17 am
shoedoos wrote: Tue Jul 10, 2018 1:06 am apologies, these are new H-series bearings I was using in the measurements.
What I was asking is how much less crush would you see on a bearing that has been in use and still looks good?
on ring refresh many times I reused the bearings if they looked good. I marked them to make sure they went back in the same location
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Re: Minimum Bearing Crush?

Post by modok »

af2 wrote: Tue Jul 10, 2018 11:17 am
shoedoos wrote: Tue Jul 10, 2018 1:06 am apologies, these are new H-series bearings I was using in the measurements.
What I was asking is how much less crush would you see on a bearing that has been in use and still looks good?
I don't really know.
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