Bearing Clearance?
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Bearing Clearance?

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    Default Bearing Clearance?

    As to not to high jack a thread, back in '09 I was having bearing issues. I was running .0025/.003 clearance turning 7500 RPM with an Eagle crank. I found that the crank was bent and replaced it with a Compstar. I was also told my clearances were to tight and I was told to use .003/.0035. They ended up at .0029/.0034. Now lately I've been reading and it seems my clearances are big and it's being recommended to use the tighter ones again. I've checked my bearings and feel I can reuse them and only replace the rings. Now I'm wondering about clearances again.

    Tim

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    Quote Originally Posted by River Rat 005 View Post
    As to not to high jack a thread, back in '09 I was having bearing issues. I was running .0025/.003 clearance turning 7500 RPM with an Eagle crank. I found that the crank was bent and replaced it with a Compstar. I was also told my clearances were to tight and I was told to use .003/.0035. They ended up at .0029/.0034. Now lately I've been reading and it seems my clearances are big and it's being recommended to use the tighter ones again. I've checked my bearings and feel I can reuse them and only replace the rings. Now I'm wondering about clearances again.

    Tim
    I actually think you answered your own question! Jocko

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    Quote Originally Posted by River Rat 005 View Post
    As to not to high jack a thread, back in '09 I was having bearing issues. I was running .0025/.003 clearance turning 7500 RPM with an Eagle crank. I found that the crank was bent and replaced it with a Compstar. I was also told my clearances were to tight and I was told to use .003/.0035. They ended up at .0029/.0034. Now lately I've been reading and it seems my clearances are big and it's being recommended to use the tighter ones again. I've checked my bearings and feel I can reuse them and only replace the rings. Now I'm wondering about clearances again.

    Tim
    I don't remember anybody saying those numbers are too big. Maybe bigger than necessary, but they will work fine with the right oil.
    You don't mention what the "too tight" clearances were. Maybe they were, maybe they weren't. The clearance you can "get away with" has a lot to do with the quality of the crankshaft and block machining.
    A less than dead nuts straight crank and dead straight align bore require sloppier clearances.,



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    The tight clearance was the .0025/.0030. Thats what I had when I built the engine in'03. '08 I took it down for inspection and found #3 rod bearing down to the copper. The crank was turned .010/.010. After that is when I had the bearing problems and later found out the crank was bent from turning the mains. The mains have been honed before I built the engine in '03. They were confurmed straight by a different machine shop when I was having the problems. Now it seems that the .0025/.003 is the recommended clearance. Just curious that there seems to be a change on what is recommended.

    Tim

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    .003 mains, .0025 rods is a very generic, safe, "performance" bearing clearance. It's not even close to tight.
    Clearances are dictated by a number of factors; oil type and weight, oil temp, HP and rpm, and the quality of parts as well as the intended usage.
    FYI... .0002" of added bearing clearance on a SB Chev can mean as much as 6 gpm more oil consumption, (more on a BB Chev) and that's just more oil flying around inside your engine and not where it should be.
    Last edited by scott foxwell; 02-01-2014 at 04:59 PM.
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    Quote Originally Posted by steelcomp View Post
    .003 mains, .0025 rods is a very generic, safe, "performance" bearing clearance. It's not even close to tight.
    Clearances are dictated by a number of factors; oil type and weight, oil temp, HP and rpm, and the quality of parts as well as the intended usage.
    FYI... .0002" of added bearing clearance on a SB Chev can mean as much as 6 gpm more oil consumption, (more on a BB Chev) and that's just more oil flying around inside your engine and not where it should be.
    But it will require him to buy another set of bearings .001 smaller and use the half shells to reduce what he has .0005.
    But then, he will have a set of bearings for the next freshen up



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    Quote Originally Posted by gn7 View Post
    But it will require him to buy another set of bearings .001 smaller and use the half shells to reduce what he has .0005.
    But then, he will have a set of bearings for the next freshen up
    Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable.
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    Quote Originally Posted by gn7 View Post
    But it will require him to buy another set of bearings .001 smaller and use the half shells to reduce what he has .0005.
    But then, he will have a set of bearings for the next freshen up
    I have a few half-sets of one unders...oh well. No one ever said this was easy or cheap (to do it right)...
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    Quote Originally Posted by Infomaniac View Post
    Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable.
    I'd like to see the data to support that.
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    Quote Originally Posted by Infomaniac View Post
    Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable.
    I was told the same. Don't know if I buy it. But it sure does make me concerned about using the left over bearings from a the x set for the next rebuild.
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    Ill take all of those leftover sets. Wouldn't want you to put some in and worry about it the whole time.
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    Quote Originally Posted by Infomaniac View Post
    Ill take all of those leftover sets. Wouldn't want you to put some in and worry about it the whole time.
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    Quote Originally Posted by Infomaniac View Post
    Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable.
    Quote Originally Posted by steelcomp View Post
    I'd like to see the data to support that.
    Quote Originally Posted by Hass828 View Post
    I was told the same. Don't know if I buy it. But it sure does make me concerned about using the left over bearings from a the x set for the next rebuild.
    Its in one of their tech bulletins. Some BS about loads blah blah blah. The mains were one way and the rods were another. The idea in the rods is a complete joke due to the delta wall. In either case, its a .00025 difference in thickness at each butting. I never had problem doing it either way and stopped worrying about that years, I think it was means to sell more bearings.

    Also, according to Clevite, .001 X journal diameter or .0021. But then +.0005 "as a margin of safety" for a starting point. WTF does that mean. A starting point heading to where. They never say. Starting point if this is your first engine? Who flock knows.


    Any how, before I would use a half set, I would send the POS out to be coated. My favorite way to rid a little clearance.
    If this thing is blown, I would still use them as is, and still have them coated. But that's me. Your mileage may very.

    Page 6 installation and fitting tips

    http://www.stealth316.com/misc/clevi...n-bearings.pdf



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    Last edited by gn7; 02-01-2014 at 10:05 PM.

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    Quote Originally Posted by Infomaniac View Post
    Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable.
    Small blocks used to come like that from GM, something about a semi-line bore.

    I saw a guy hone a little extra on the big end to get a little more clearance,probably not the right way but it hasn't caused any problems so far.

    If i remember correctly GM calls .001 minimum on rods....fine for a basic mo ho but in a boat it will start pitching parts after a few min. @ 5500. 2.199 crank and std brngs and the dummy who assembled it didn't double check machine shop.

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