Measuring Bearing Clearances - Help
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From: Upstate NY
Originally Posted by MadBill
Speaking of temperature effects, I calculated this three times because it seems surprisingly high, but with a coefficient of thermal expansion of 7 parts per million per degree F., a 3" main journal (OK, maybe no one here's doing Pontiacs but it's a nice round number...), warmed from the previously mentioned minus 40 F. to plus 70 F., would expand 7 x 3 x 110 = 2310/1,000,000 or over two thousandths of an inch! Proportionally, a 2 tenths change would result from a mere 10 degree difference, so the combination of a cool crank and a micrometer clenched in the hot sweaty fist of the builder is of much more than just theoretical concern...
If we get a crank delivered by UPS it's usually just about the outside temp (25F today), so it has to soak in the shop air for 8 hours or more to get to a temp to measure it. I'm not sure I'd want to measure one @ -40F!
Hot honing a block presents a measurement challenge. Sure, with 6.8 millionths/in/F for cast iron, a 4.030 bore hot-honed @ 230F should be about .0038 bigger than it will be at 70F room temp. The bore gage is about 70F before you put it in the hole, but heat transfer thru the gage tips into the bore gage happens quickly. I suppose you could have a setting ring to recheck the bore gage thermal growth as soon as you pulled it out of the hot bore, but it still seems like a challenge to get exact size.
Teching In
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From: Alaska
Couldn’t agree more with the “feel” statements. I suggest playing with standards for a while prior to measuring a journal. Especially as tight as clearances are getting anymore.
Also, make damn sure whatever your measuring is clean. Very clean. I like to keep a few cans of electric motor cleaner around just for this.
The marks your bore gauge is leaving on the bearings is normal, no matter how gentle you are. If your not leaving them on H or coated bearings, your doing something wrong. I usually take scotch bright to my bearings, so the marks get removed anyway.
Also, make damn sure whatever your measuring is clean. Very clean. I like to keep a few cans of electric motor cleaner around just for this.
The marks your bore gauge is leaving on the bearings is normal, no matter how gentle you are. If your not leaving them on H or coated bearings, your doing something wrong. I usually take scotch bright to my bearings, so the marks get removed anyway.
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Just for giggles, I looked up what the accepted linear expansion rates are for a couple of materials. #'s are from Machinery's Handbook, 17th edition (1964, but some things don't change that much)
Steel: 0.00000633 inch expansion per inch per degree F
Cast Iron: 0.00000655 inch expansion per inch per degree F
Aluminum: 0.00001244 inch expansion per inch per degree F
Makes me think that an aluminum block is going to move around a bunch at temperature. For example a 9.240" deck height at room temperature (70°F) is all of a sudden going to be 0.015" taller at 200°F. And shorter at lower temperatures (luckily not enough to eat up the quench space since the reduction in height is about .012" at -30°F).
All the mixed materials involved these days really makes one think hard about building an engine. Have to decide exactly what clearances are needed, especially considering the materials involved and the operating environment they will see. Makes something that seems trivial (yeah, I've got a balanced & blueprinted motor....) a lot more tricky when you start really looking hard at it from an engineering standpoint.
'JustDreamin'
Steel: 0.00000633 inch expansion per inch per degree F
Cast Iron: 0.00000655 inch expansion per inch per degree F
Aluminum: 0.00001244 inch expansion per inch per degree F
Makes me think that an aluminum block is going to move around a bunch at temperature. For example a 9.240" deck height at room temperature (70°F) is all of a sudden going to be 0.015" taller at 200°F. And shorter at lower temperatures (luckily not enough to eat up the quench space since the reduction in height is about .012" at -30°F).
All the mixed materials involved these days really makes one think hard about building an engine. Have to decide exactly what clearances are needed, especially considering the materials involved and the operating environment they will see. Makes something that seems trivial (yeah, I've got a balanced & blueprinted motor....) a lot more tricky when you start really looking hard at it from an engineering standpoint.
'JustDreamin'
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From: Tinker till it blows, then back it off a notch, maybe!!
Originally Posted by JustDreamin
Just for giggles, I looked up what the accepted linear expansion rates are for a couple of materials. #'s are from Machinery's Handbook, 17th edition (1964, but some things don't change that much)
Steel: 0.00000633 inch expansion per inch per degree F
Cast Iron: 0.00000655 inch expansion per inch per degree F
Aluminum: 0.00001244 inch expansion per inch per degree F
Makes me think that an aluminum block is going to move around a bunch at temperature. For example a 9.240" deck height at room temperature (70°F) is all of a sudden going to be 0.015" taller at 200°F. And shorter at lower temperatures (luckily not enough to eat up the quench space since the reduction in height is about .012" at -30°F).
All the mixed materials involved these days really makes one think hard about building an engine. Have to decide exactly what clearances are needed, especially considering the materials involved and the operating environment they will see. Makes something that seems trivial (yeah, I've got a balanced & blueprinted motor....) a lot more tricky when you start really looking hard at it from an engineering standpoint.
'JustDreamin'
Steel: 0.00000633 inch expansion per inch per degree F
Cast Iron: 0.00000655 inch expansion per inch per degree F
Aluminum: 0.00001244 inch expansion per inch per degree F
Makes me think that an aluminum block is going to move around a bunch at temperature. For example a 9.240" deck height at room temperature (70°F) is all of a sudden going to be 0.015" taller at 200°F. And shorter at lower temperatures (luckily not enough to eat up the quench space since the reduction in height is about .012" at -30°F).
All the mixed materials involved these days really makes one think hard about building an engine. Have to decide exactly what clearances are needed, especially considering the materials involved and the operating environment they will see. Makes something that seems trivial (yeah, I've got a balanced & blueprinted motor....) a lot more tricky when you start really looking hard at it from an engineering standpoint.
'JustDreamin'
Also, steel or iron mains on an aluminum block. What is happening there?
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Yes, I brought up the quench/squish thing re aluminum blocks in another ls1 thread. Much of the lore re how tight you can run is from iron SBC block experiences; you should be able to safely run at least 0.006" less in an aluminum block.
Speaking again of expansion (Holy thread hijack, Batman!), a prestigious US Porsche tuner a few years ago was going through valve lash loops on an air-cooled 911 mill on the dyno and gaining power each time they closed them down. They knocked off for lunch and when they returned, couldn't get the engine started. Eventually discovered there was no compression, due to negative cold lash...
Speaking again of expansion (Holy thread hijack, Batman!), a prestigious US Porsche tuner a few years ago was going through valve lash loops on an air-cooled 911 mill on the dyno and gaining power each time they closed them down. They knocked off for lunch and when they returned, couldn't get the engine started. Eventually discovered there was no compression, due to negative cold lash...
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From: Upstate NY
Originally Posted by JustDreamin
Just for giggles, I looked up what the accepted linear expansion rates are for a couple of materials. #'s are from Machinery's Handbook, 17th edition (1964, but some things don't change that much)
Steel: 0.00000633 inch expansion per inch per degree F
Cast Iron: 0.00000655 inch expansion per inch per degree F
Aluminum: 0.00001244 inch expansion per inch per degree F
Makes me think that an aluminum block is going to move around a bunch at temperature. For example a 9.240" deck height at room temperature (70°F) is all of a sudden going to be 0.015" taller at 200°F. And shorter at lower temperatures (luckily not enough to eat up the quench space since the reduction in height is about .012" at -30°F).
All the mixed materials involved these days really makes one think hard about building an engine. Have to decide exactly what clearances are needed, especially considering the materials involved and the operating environment they will see. Makes something that seems trivial (yeah, I've got a balanced & blueprinted motor....) a lot more tricky when you start really looking hard at it from an engineering standpoint.
'JustDreamin'
Steel: 0.00000633 inch expansion per inch per degree F
Cast Iron: 0.00000655 inch expansion per inch per degree F
Aluminum: 0.00001244 inch expansion per inch per degree F
Makes me think that an aluminum block is going to move around a bunch at temperature. For example a 9.240" deck height at room temperature (70°F) is all of a sudden going to be 0.015" taller at 200°F. And shorter at lower temperatures (luckily not enough to eat up the quench space since the reduction in height is about .012" at -30°F).
All the mixed materials involved these days really makes one think hard about building an engine. Have to decide exactly what clearances are needed, especially considering the materials involved and the operating environment they will see. Makes something that seems trivial (yeah, I've got a balanced & blueprinted motor....) a lot more tricky when you start really looking hard at it from an engineering standpoint.
'JustDreamin'
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Originally Posted by rjw
We must of taken a wrong turn in Albuquerque.
I don't know that we're terribly off topic. But I'm not sure if the original question got answered fully.
'JustDreamin'
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Back to the main topic... Lets say I found that one of my mains has a clearance of .0012", which from what I've read would be an acceptable tolerance... Does this mean that .0012" is the clearance between the crank journal and the bearing surface on both sides... meaning there is actually .0006" of spacing between the journal surface and the bearing surface?
Also, LME said that they shoot for a clearance of .0007" to .0021" on their main bearings. Is anywhere in that range acceptable, or will .0007" have a lot of friction and .0021" have little oil pressure? I assume the middle of the range like .0014" would be a great clearance to have?
Final question, are the goal clearances on the main AND rod bearings the same? Thanks!
Also, LME said that they shoot for a clearance of .0007" to .0021" on their main bearings. Is anywhere in that range acceptable, or will .0007" have a lot of friction and .0021" have little oil pressure? I assume the middle of the range like .0014" would be a great clearance to have?
Final question, are the goal clearances on the main AND rod bearings the same? Thanks!
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From: Tinker till it blows, then back it off a notch, maybe!!
Originally Posted by Ferocity02
Back to the main topic... Lets say I found that one of my mains has a clearance of .0012", which from what I've read would be an acceptable tolerance... Does this mean that .0012" is the clearance between the crank journal and the bearing surface on both sides... meaning there is actually .0006" of spacing between the journal surface and the bearing surface?
Also, LME said that they shoot for a clearance of .0007" to .0021" on their main bearings. Is anywhere in that range acceptable, or will .0007" have a lot of friction and .0021" have little oil pressure? I assume the middle of the range like .0014" would be a great clearance to have?
Final question, are the goal clearances on the main AND rod bearings the same? Thanks!
Also, LME said that they shoot for a clearance of .0007" to .0021" on their main bearings. Is anywhere in that range acceptable, or will .0007" have a lot of friction and .0021" have little oil pressure? I assume the middle of the range like .0014" would be a great clearance to have?
Final question, are the goal clearances on the main AND rod bearings the same? Thanks!
Clearances would depend on your application. Give details...
I will say that I would never run 7 tenths on anything, but that's just me.
Originally Posted by rjw
That is correct. 6 tenths per side for a total of 1.2 thou...
Clearances would depend on your application. Give details...
I will say that I would never run 7 tenths on anything, but that's just me.
Clearances would depend on your application. Give details...
I will say that I would never run 7 tenths on anything, but that's just me.
My application is a NA street motor, aiming for around 550rwhp. There is a slight chance of a little N20, but that won't be for awhile. I am looking for reliability, long life, and good oil pressure(40+psi), and ofcourse good power. Basically, I think halfway in between acceptably tight and acceptably loose, if that makes sense. I would prefer the motor be built tighter than looser.
Originally Posted by Ferocity02
Back to the main topic... Lets say I found that one of my mains has a clearance of .0012", which from what I've read would be an acceptable tolerance... Does this mean that .0012" is the clearance between the crank journal and the bearing surface on both sides... meaning there is actually .0006" of spacing between the journal surface and the bearing surface?
Also, LME said that they shoot for a clearance of .0007" to .0021" on their main bearings. Is anywhere in that range acceptable, or will .0007" have a lot of friction and .0021" have little oil pressure? I assume the middle of the range like .0014" would be a great clearance to have?
Final question, are the goal clearances on the main AND rod bearings the same? Thanks!
Also, LME said that they shoot for a clearance of .0007" to .0021" on their main bearings. Is anywhere in that range acceptable, or will .0007" have a lot of friction and .0021" have little oil pressure? I assume the middle of the range like .0014" would be a great clearance to have?
Final question, are the goal clearances on the main AND rod bearings the same? Thanks!
If we are talking cast iron block for an LS1, we generally set up the mains at
.0024"- .0027". This will give you great oil pressure and durability. On aluminum we like the mains to be a bit tighter.
I would not run the mains as tight as .0007".
If you have ever checked a stock aluminum LS1. You may be suprised how tight they will run.
Originally Posted by Ferocity02
Thanks for the help! I agree that 7 tenths seems like practically no space at all, even for a thin layer of oil.
My application is a NA street motor, aiming for around 550rwhp. There is a slight chance of a little N20, but that won't be for awhile. I am looking for reliability, long life, and good oil pressure(40+psi), and ofcourse good power. Basically, I think halfway in between acceptably tight and acceptably loose, if that makes sense. I would prefer the motor be built tighter than looser.
My application is a NA street motor, aiming for around 550rwhp. There is a slight chance of a little N20, but that won't be for awhile. I am looking for reliability, long life, and good oil pressure(40+psi), and ofcourse good power. Basically, I think halfway in between acceptably tight and acceptably loose, if that makes sense. I would prefer the motor be built tighter than looser.
Originally Posted by Beast96Z
FWIW, with the crank that was in that motor, they showed .0024" on the main bearings and .0022" on the rod bearings. Depending on how close the Eagle crank is in diameter to the Lunati, I'd look for the clearence to be similar with the same bearings.
Originally Posted by Old SStroker
It depends. Set a bore gage and have 5 people measure a hole. Then give 5 people a T-gage and the same micrometer used to set the bore gage and have them measure the same hole. I'll bet the range of sizes with the T-Gage is 2-3 times the range of the bore gage measurement. As in many things, "feel" is important.
My $.02
My $.02
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From: Berkeley, California
Resurrecting a very old thread because I appreciate good information. I am a machine shop class dropout who knows how elusive accurate measurements can be. rjw's micrometer lesson is excellent.
On The Tree
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Makes me think that an aluminum block is going to move around a bunch at temperature. For example a 9.240" deck height at room temperature (70°F) is all of a sudden going to be 0.015" taller at 200°F. And shorter at lower temperatures (luckily not enough to eat up the quench space since the reduction in height is about .012" at -30°F).
Now imagine that the torque + angle sequence for those fasteners had been determined by GM engineers after taking thermal expansion into account.
What temp is the engine when the fasteners are tightened? Yours was at the same temp, right? ...right? What? You assembled your aluminum engine in a 30degree garage? Wooops....
