08-05-2014, 06:51 AM | #1 |
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Bearing crush
Hi can anyone tell how much bearing crush for mains and con rods engine is 8BA any info welcome
I believe it should be 0.004 - 0.005 I have read the instruction that come with the bearings no mention of crush checked most of my books can not find anything Last edited by colin1928; 08-05-2014 at 08:05 AM. Reason: add |
08-05-2014, 08:39 AM | #2 |
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Re: Bearing crush
This will tell you what you need to know plus more.
http://www.secondchancegarage.com/public/406.cfm Last edited by 19Fordy; 08-05-2014 at 11:47 AM. |
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08-05-2014, 08:49 AM | #3 |
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Re: Bearing crush
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08-05-2014, 09:21 AM | #4 |
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Re: Bearing crush
Working with my machine shop we usually end up with .0015" to .002" Seems to work out quite well. I always check all with plasti gage.
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08-05-2014, 09:28 AM | #5 |
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Re: Bearing crush
If you are attempting an online search, the word "crush" may not turn up what you are looking for, the normal specification term is "clearance". .004 - .005 would be way to loose. By the way, these numbers are normally given in inches, not millimeters (sure you already knew that, but just to be on the safe side). Think 4tford has the correct clearances and I agree, check it with plasti gage.
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08-05-2014, 12:59 PM | #6 | |
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Re: Bearing crush
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Quote:
If you want to find out about bearing crush, look up bearing crush. It's where the bearings are slightly over half the Rod or main bore. They sit a tickle proud of the caps before torque down. When you torque the cap, the bearing shell is forced hard into the bore, making it fit real good. This is a simplified explanation. To show that it's different to clearance. Martin. |
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08-05-2014, 04:54 PM | #7 |
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Re: Bearing crush
Normally the bearing catalogs had the bore of the main bearings and the bore of the connecting rods listed in them ( the crush was engineered in ) you would then check Main bearing with a dial bore gauge and for rods a Sunnen AG-300 Precision gauge (Arnold Gauge). Sunnen Gauge below.
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08-05-2014, 05:08 PM | #8 | |
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Re: Bearing crush
Quote:
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08-05-2014, 05:41 PM | #9 |
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Re: Bearing crush
I've not heard much about crush in automotive engines but have a lot of experiance with aircraft engines that do. Lycoming has two different types of bearings for their opposed engines. The lower horse power slower rpm engines have high crush bearings that have a relatively thin bearing shell thickness. The high horsepower & high rpm engines have heavy (thick wall) low crush bearing shells that are also pinned in the bore to keep them from shifting around. Both crush a bit but the thin ones are designed to crush more than the thick ones.
This is all designed in to the individual applications and there is no adjustment of the "crush" that I am aware of. |
08-05-2014, 07:16 PM | #10 |
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Re: Bearing crush
I used to cut bearings for years back in the 60-70 we used to get semi bearing and could cut any size you wanted, the bearing are about .001 thinner on the sides then in the middle, when you torque them down in the block or rod cap they squeeze together or crush. You can't check that with plastic gauge you have to use a mic. If you talking about clearance .002 is about right for a stock engine. My brother used to go out on the road and turn a rod journal on a truck that had spun a rod bearing with a portable crank grinder, he would call me with what size and I'd cut a bearing to fit it. That's a dead occupation now. Walt
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08-05-2014, 07:41 PM | #11 | |
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Re: Bearing crush
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Yup x2 R |
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08-06-2014, 12:41 AM | #12 |
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Re: Bearing crush
Thanks guys got what I needed to measure nip and crush
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08-06-2014, 01:25 AM | #13 | |
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Re: Bearing crush
Quote:
Have a look at the clevite link, or Google it, there's info out there that can explain it far better than me. There's far more to it than you'd believe. Martin. |
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08-06-2014, 09:14 AM | #14 |
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Re: Bearing crush
Interesting thread, learned allot. The clearance if a stock bearing is also designed for the oil viscosity. This .0015/.002 is why a thinner oil is necessary to improve flow through the bearing for cooling. Racing engines have larger clearances (.0025/.003) and thus a thicker oil can be used. You might re think 20/50 oil for a street engine.
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