Minimum Bearing Crush?

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crazy_caseys_customs
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Minimum Bearing Crush?

Post by crazy_caseys_customs » Sun May 27, 2018 10:37 pm

I’m assembling a mild 289 Ford. The block was line-honed, but I’m not ultra confident in the quality of the work. I’m measuring as much a half a thou outside of the spec, but my measuring tools are not the absolute best. I’m assembling the motor, and I have attempted to measure bearing crush, and I’m just not seeing very much.

Essentially what I am doing is putting the bearing shell in the block and cap, respectively. In the block, I am taking a main cap, laying it over one side of the bearing at a 90, and snugging it down. Then I am removing the cap and using a 1-2-3 block and a feeler gauge to measure how far the bearing is proud from the block surface on the opposite side. I’m getting a measurement of 0.007-0.008”.

The bearings in the caps are all very slightly below the surface. I have a granite surfacing table, and can press the cap against the table, and feel the slightest drag on a 0.0015” feeler gauge between the edge of the bearing and the granite.

So all told I’ve got about 0.005-0.0065” bearing crush. I always thought you were supposed to have like 0.015-0.020”. And this is with Clevite H series bearings, which are supposed to have a high crush factor. What is considered the minimum?

FWIW, main bearing bore is 2.442-2.4425”.

I really appreciate the help.

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Re: Minimum Bearing Crush?

Post by modok » Mon May 28, 2018 1:06 am

The way you are doing it is overcomplicated.

Put the bearings in, put the cap on the block. Tighten one size to 30% or... 50%? of full torque, enough that there is NO gap under that side.
Snug the other side to a few foot pounds. Measure the gap between cap and block on that side.
This is probably the method used if the specification you are looking for is such a large value, although I'm not really sure if it is correct.
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Re: Minimum Bearing Crush?

Post by crazy_caseys_customs » Mon May 28, 2018 1:21 am

modok wrote:
Mon May 28, 2018 1:06 am
The way you are doing it is overcomplicated.

Put the bearings in, put the cap on the block. Tighten one size to 30% or... 50%? of full torque, enough that there is NO gap under that side.
Snug the other side to a few foot pounds. Measure the gap between cap and block on that side.
This is probably the method used if the specification you are looking for is such a large value, although I'm not really sure if it is correct.
Thanks for replying. I’ll have to try that.

After I posted I saw this:
0CAD39B9-40F6-4004-AB09-AB501D56F20C.jpeg
That makes me think I’m not so far off.
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Re: Minimum Bearing Crush?

Post by modok » Mon May 28, 2018 4:36 am

I think a good press-fit, by diameter, is .001" per inch.
So, 2.4" housing.......so about .0024"
at the circumference that would be (times pie), .0076 total, or .0038 per shell

minimum? educated guess, .0006 per inch.
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Re: Minimum Bearing Crush?

Post by crazy_caseys_customs » Mon May 28, 2018 7:33 am

modok wrote:
Mon May 28, 2018 4:36 am
I think a good press-fit, by diameter, is .001" per inch.
So, 2.4" housing.......so about .0024"
at the circumference that would be (times pie), .0076 total, or .0038 per shell

minimum? educated guess, .0006 per inch.
You accused me of “overcomplicating”...I do that. What you said falls fairly closely in line with what King published which falls fairly closely in line with what I’m measuring.

I originally got the numbers I posted from an article on Muscle Car DIY, but I’m thinking now they must have missed a zero.

https://www.musclecardiy.com/performanc ... ngs-guide/
E5084404-B0BC-41DF-A3B9-0F3402D4CEE9.jpeg
4E11C75D-DE2F-487F-81B9-FAE523300289.jpeg
So my only question/concern now, is should I be at all concerned that the main cap side has no discernible crush at all? I get that when I put the two sides together I will have crush. It just seems that the line hone must have removed more material from the cap side than the block side.

Again, thanks for thinking through this with me. I was all spun up.
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Re: Minimum Bearing Crush?

Post by Warp Speed » Mon May 28, 2018 11:46 am

Minimum should be around .0045, and max .006-.007 depending on shell thickness. Any more can start to distort the bearing, any less and you can get bearing movement.

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Re: Minimum Bearing Crush?

Post by crazy_caseys_customs » Mon May 28, 2018 12:17 pm

Warp Speed wrote:
Mon May 28, 2018 11:46 am
Minimum should be around .0045, and max .006-.007 depending on shell thickness. Any more can start to distort the bearing, any less and you can get bearing movement.
Is that per shell or total? What is your take on the bearings in my caps being recessed and the bearings in my block being proud?

What you’re saying jives if your numbers are total and King’s are per shell. There seems to be a lot of conflicting/misleading information floating around out there. I’m wondering how many people actually check their bearing crush...

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Re: Minimum Bearing Crush?

Post by Newold1 » Mon May 28, 2018 2:34 pm

All good answers here!

If the block was line bored or line honed any substantial amount the main caps will normally be shaved just slightly to bring the required crush back in line. If your block had this type of machining make sure to look at the bottom of the main caps and see whether they were touched slightly.

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Re: Minimum Bearing Crush?

Post by MotionMachine » Mon May 28, 2018 3:00 pm

In a perfect world, parting line to saddle depth would be the same for the cap and the block. But it's not and it doesn't matter that the actual bore is not exactly in the middle of the block/cap. This is why measuring total crush, as in the King example, eliminates any confusion with negative crush on one or the other.

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Re: Minimum Bearing Crush?

Post by Warp Speed » Mon May 28, 2018 4:27 pm

crazy_caseys_customs wrote:
Mon May 28, 2018 12:17 pm
Warp Speed wrote:
Mon May 28, 2018 11:46 am
Minimum should be around .0045, and max .006-.007 depending on shell thickness. Any more can start to distort the bearing, any less and you can get bearing movement.
Is that per shell or total? What is your take on the bearings in my caps being recessed and the bearings in my block being proud?

What you’re saying jives if your numbers are total and King’s are per shell. There seems to be a lot of conflicting/misleading information floating around out there. I’m wondering how many people actually check their bearing crush...
That is total for both shells.

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Re: Minimum Bearing Crush?

Post by BillK » Mon May 28, 2018 5:07 pm

Sorry guys, I don't see any of the above mentioned methods can really be that accurate. The real way to do it is to bolt the cap on the block and measure the id of the bearing housing with a bore gauge. That way you can also see if there is any taper. I you don't feel comfortable with that or don't have the correct tools then bolt the caps on and take the block to the guy that align honed it for you and have him check it while you are there. If you have the caps on it shouldn't take more than ten minutes.

As far as the amount of crush, I pretty much stick with the bore housing sizes that the bearing manufacturer gives and prefer to have them on the small end of specs.
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Re: Minimum Bearing Crush?

Post by modok » Mon May 28, 2018 5:40 pm

It seems logical to the layperson, that the split will be perfectly on center of the bore.
Once you get your feet wet in the machining world you learn that things that don't need to be precise.....aren't. Heck this is a ford. If there was any company that took that to the extreme it would be ford. :lol:


98% of the time the split is random located somewhere near the center. The remaining 2% comprises luck, rare antiques, and some things made in Germany.

In fact I got so used to the split NOT being in the center, that when I was confronted with a rare case that the split DID need to be in the center.........I was dumbfounded, and I it took me quite a while to come up with new tools and procedures to make it happen. The reason the split needed to be in the center was because this ancient design used solid shims to adjust the clearance, and the shims extended and sat between the parting of the bearing shells.
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Re: Minimum Bearing Crush?

Post by modok » Mon May 28, 2018 5:44 pm

Another way to measure crush is take the measured ID of the bearings in place, and compare it with the housing size minus 2x measured bearing thickness. The measured ID will always be some degree larger than the....lets call it...."theoretical ID", because the interference fit forces the housing BIGGER with the bearings in place.
There is no standard to compare against, but it does work.

The company that makes the bearings specifies what size holes they will fit. Usually, you trust this, and all is well. If you are a bit outside the range specified, AND/OR you do not trust the bearing company, it will be useful to know how to check the crush.
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Re: Minimum Bearing Crush?

Post by Newold1 » Mon May 28, 2018 10:44 pm

We seem to be getting into an involved discussion on the condition of mainline dimensions or measurement but what seems to be possibly the situation as posted by the OP here is that there is a definite situation here that the crush is non-existent or inadequate. The OP has not indicated that the block was line bored or line honed. If it was and the main bore was not accurately measured and then brought back to the stock specification this would affect crush and until the main bore dimension is now accurately measured it will be possible that correct crush does not now exist and it will not fix itself if the main bore dimension is not correct or brought back to the correct dimension. :?

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Re: Minimum Bearing Crush?

Post by modok » Mon May 28, 2018 11:33 pm

crazy_caseys_customs wrote:
Sun May 27, 2018 10:37 pm
.....The block was line-honed, but I’m not ultra confident in the quality of the work.
.....FWIW, main bearing bore is 2.442-2.4425”.
nothing on a old ford is REALLY +/- .00025, so I read that spec, and mentally change it to 2.4420-2.2430, right away, out of habit.
The clevite bearing company does the same thing.
They specifications in the clevite catalog are OE specifications, however it is also noted in the catalog that they manufacture their bearings to what they feel is maximum crush at the minimum size. This is also true of the clearance specifications. The clearance specifications are OE, but if the bearings are a different material than OE they may in fact need different clearance than specified.
You may find this confusing, but I think it is the better way. if each company printed slightly different specifications it would result in chaos, and really when that has happened it HAS created chaos. So I think they made the right choice to keep the specifications the same as OE, even though they don't necessarily apply to the bearings they make, strange as that is, that's how it is, or rather how it has been. The future is a mystery.

BUT what about KING???? How do THEY interpret this overly precise specification? Beats me. I've had three cases where king bearings had the crush wrong, a subaru, a MG, and another that escapes me. I don't know what it means, but basically I don't trust them. If anybody does know, do tell.
Glen Urban

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