Proper method for determining bearing clearances?

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ValiantOne

ValiantOne

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I'm going to start assy on my 5.9 magnum this weekend. I have my bearings from Hughes, prepped block and polished crank.

I am aware of plastigauge, but don't have any. What I do have is a full set of inside and outside micrometers, snap gauges, gauge blocks, dial bore gauge, etc (I am a machinist, just not automotive)

I am guessing that I put my bearings in place, torque to spec, take several readings around the circumference, then measure the rod/main journal and do the math.

Is that about right?

Thanks for any pointers.

CE
 
I would think that the most important directions are parallel and perpendicular to the joint face... (top and sides)...

But yeah, torque to spec and then measure with micrometers...


Plastic gauge is easy, they should have some at the parts store - get the green one if you go that direction...
 
ValiantOne said:
I'm going to start assy on my 5.9 magnum this weekend. I have my bearings from Hughes, prepped block and polished crank.

I am aware of plastigauge, but don't have any. What I do have is a full set of inside and outside micrometers, snap gauges, gauge blocks, dial bore gauge, etc (I am a machinist, just not automotive)

I am guessing that I put my bearings in place, torque to spec, take several readings around the circumference, then measure the rod/main journal and do the math.

Is that about right?

Thanks for any pointers.

CE
Click to expand...
Summit Racing sells it as does napa. i paid 1.99 for mine
 
ValiantOne said:
I'm going to start assy on my 5.9 magnum this weekend. I have my bearings from Hughes, prepped block and polished crank.

I am aware of plastigauge, but don't have any. What I do have is a full set of inside and outside micrometers, snap gauges, gauge blocks, dial bore gauge, etc (I am a machinist, just not automotive)

I am guessing that I put my bearings in place, torque to spec, take several readings around the circumference, then measure the rod/main journal and do the math.

Is that about right?

Thanks for any pointers.

CE
Click to expand...


Tighten them once and leave them tightened until you are ready to assemble... Every time you torque the bolts/nuts they stretch...

They recommend only 5 clamp cycles on each bolt before replacing... If you replace the rod bolts, you need to recondition that end...

Keep them secure in case you need to re-check your readings later...
 
krazykuda said:
If he's a machinist, he may prefer using micrometers...
Click to expand...
you can still use micrometers, i was just saying if he wanted to check the torqued down clearances, he can get plastigauge.
 
I always did both hard measurement and plastgage, but have never seen plastigage go wrong.

For standard production tolerance it should be fine and will show taper quite well.

I don't know how much error is standard with snap gauges and mics, or dbg's. Lots of operator variance on that.
 
Either method will work...

The micrometer method is a little more accurate if done properly...

Plastic gauge is easier to do "in the garage"....
 
jos51700 said:
I always did both hard measurement and plastgage, but have never seen plastigage go wrong.

For standard production tolerance it should be fine and will show taper quite well.

I don't know how much error is standard with snap gauges and mics, or dbg's. Lots of operator variance on that.
Click to expand...

Just be careful how many times you tighten the crank and rod bolts, so they don't get overstretched and will fail....

And you don't want one of those to fail....

It is recommended that you only tighten a main or rod bolt 5 times, then replace.... After that you are taking chances...
 
krazykuda said:
Just be careful how many times you tighten the crank and rod bolts, so they don't get overstretched and will fail....

And you don't want one of those to fail....

It is recommended that you only tighten a main or rod bolt 5 times, then replace.... After that you are taking chances...
Click to expand...

While I'm not a fan of reusing rod bolts, this is the first time in my life I've ever heard this (tty fasteners excluded).

If properly torqued, any given fastener can be reused countless times because it never goes into plastic deformation.

How many times have you replaced wheel studs on your vehicles? ;-)
 
jos51700 said:
While I'm not a fan of reusing rod bolts, this is the first time in my life I've ever heard this (tty fasteners excluded).

If properly torqued, any given fastener can be reused countless times because it never goes into plastic deformation.

How many times have you replaced wheel studs on your vehicles? ;-)
Click to expand...

I used to set-up the torquing stations in an engine factory...

I've done bolt stretch studies... They stretch a little every time you torque them...

If you do not go into plastic deformation, you are not getting proper clamp load... It's the stretching of the bolt that provides the maximum clamp...


If you want to torque yours repeatedly, go ahead, but don't be surprised if it ever blows up....

If it does, it will take out the block and crank minimum... Is it worth the price of new bolts to blow up an engine...


How many sets of tires does a car go through before it's past it's useful life???
 
Dial bore gauge is best. Set it to the size of the crank, then measure the torqued bearings to get your clearances.
 
lilcuda said:
Dial bore gauge is best. Set it to the size of the crank, then measure the torqued bearings to get your clearances.
Click to expand...

Dial bore gauges or inside ball micrometers for bearings, I like dial bore gauges if available... :thumbsup:

Micrometer for crank....
 
lilcuda said:
Of course. You mic the crank, then set the dial bore gauge with that mic, then measure your bearings. :thumbsup:
Click to expand...

We had dedicated dial bore gauges with "master" gauge rings set to the bore diameter that we were checking....

Always verify your gauges before measuring parts...

Anybody could have dropped or bumped the gauge and thrown off it's calibration..
 
krazykuda said:
We had dedicated dial bore gauges with "master" gauge rings set to the bore diameter that we were checking....

Always verify your gauges before measuring parts...

Anybody could have dropped or bumped the gauge and thrown off it's calibration..
Click to expand...

Dial bore gauges change when you breathe on them! Yes, always set up a standard and test. At home I dont have a way to stack up a decent standars so I use a mic which has been set with a gauge block. Not perfect but close enough for this kind of work.

In fact I was going to do some measuring of the bores last night but i had left the block out in the sun. It was hot! My tools were down in the basement, nice and cool. Not a good combo for accurate measurements.
 
ValiantOne said:
Dial bore gauges change when you breathe on them! Yes, always set up a standard and test. At home I dont have a way to stack up a decent standars so I use a mic which has been set with a gauge block. Not perfect but close enough for this kind of work.

In fact I was going to do some measuring of the bores last night but i had left the block out in the sun. It was hot! My tools were down in the basement, nice and cool. Not a good combo for accurate measurements.
Click to expand...

Yeah, it's best to measure them at room temperature....

However, it doesn't matter what temperature the room is - it's always at room temperature.... :rolleyes:

If you feel cold, go sit in the corner - they are 90°.... :rolleyes:
 
krazykuda said:
I used to set-up the torquing stations in an engine factory...

I've done bolt stretch studies... They stretch a little every time you torque them...

If you do not go into plastic deformation, you are not getting proper clamp load... It's the stretching of the bolt that provides the maximum clamp...


If you want to torque yours repeatedly, go ahead, but don't be surprised if it ever blows up....

If it does, it will take out the block and crank minimum... Is it worth the price of new bolts to blow up an engine...


How many sets of tires does a car go through before it's past it's useful life???
Click to expand...

Ha, now you got me all paranoid. The machine shop used the main bolts to hold the block in the honing machine, etc. There has to be at least two or thee cycles on them at this point... I'm gonna use em' but I won't sleep well tonight.....:BangHead:

Incidentally, I just replaced all of the wheel studs on my 2013 impala after 3 of them went soft while torquing to spec. Cheap crap!
 
krazykuda said:
I used to set-up the torquing stations in an engine factory...

I've done bolt stretch studies... They stretch a little every time you torque them...

If you do not go into plastic deformation, you are not getting proper clamp load... It's the stretching of the bolt that provides the maximum clamp...


If you want to torque yours repeatedly, go ahead, but don't be surprised if it ever blows up....

If it does, it will take out the block and crank minimum... Is it worth the price of new bolts to blow up an engine...


How many sets of tires does a car go through before it's past it's useful life???
Click to expand...
And I'm the engineer that determines how tight you tighten the bolts at the torque station. If you take it to plastic deformation, you done fucked it.

Every bolt stretches when tightened, that's how they work. The key is to NOT tighten it to the point that they don't restore themselves. If it stretches and can't return to it's original dimension, it's experienced plastic deformation.

At that point, it's "gone soft" as a previous poster put it.

The bolt tension should only be eighty to ninety percent of its yield strength, depending on application.

Think about your lug studs. If you had to replace them every five uses, you'd never make it to a new set of tires without replacing studs, assuming you rotate your tires when recommended.

Rods and mains' bolts have a limited re -use spec due to the fatigue nature of the application; fully torque they're still seeing cyclic stress thousand of times a minute.

If you tightened them to the plastic deformation point they would not last an hour.

Screenshot_2017-06-30-15-51-28.png
 
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Don't worry about it one second more. These old bolts have a lot of life in them. Rod bolts can be a point of failure but mains bolts tend to not be so. Examine them carefully for 'necking' and damaged threads; side by side comparisons can be useful. If it bothers you enough, just buy new and start fresh.

Honestly, I dunno HOW many times I reused my Opel and Mitsu racing engine rod and mains bolts... the former revved to 8K all day long and the latter was 14-15 psi boosted.

FWIW... plastigage is all over the place and does not go 'out of calibration' LOL
 
ValiantOne said:
Ha, now you got me all paranoid. The machine shop used the main bolts to hold the block in the honing machine, etc. There has to be at least two or thee cycles on them at this point... I'm gonna use em' but I won't sleep well tonight.....:BangHead:

Incidentally, I just replaced all of the wheel studs on my 2013 impala after 3 of them went soft while torquing to spec. Cheap crap!
Click to expand...

Rest easy, they are good for millions of cycles if not abused.

Or.....ARP! (With resizing)
 
jos51700 said:
And I'm the engineer that determines how tight you tighten the bolts at the torque station. If you take it to plastic deformation, you done fucked it.

Every bolt stretches when tightened, that's how they work. The key is to NOT tighten it to the point that they don't restore themselves. If it stretches and can't return to it's original dimension, it's experienced plastic deformation.

At that point, it's "gone soft" as a previous poster put it.

The bolt tension should only be eighty to ninety percent of its yield strength, depending on application.
Click to expand...


Do a bolt stretch study to prove it...

Take both ends of the rod bolts and have them ground flat and parallel, then have centers put in so your micrometers measure EXACTLY on center...

Run them through your equipment and record the tightening data, torque and angle and any other parameters that you measure...

Then take them apart and re-measure with ball mic's and if you torque to spec, there will be a small amount of permanent deformation usually about .0005"-.0015" per cycle....
 
I measure the journal for the bearing I want to check tolerance on, lock the mike to hold the reading, zero my Dial bore gauge to the mike, then check the bearing. If you do it all carefully, it is pretty much fool proof, because you are doing a direct measurement of the difference, and you are not depending on the mike being dead accurate and perfectly calibrated.
 
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