how do i measure bearing clearances??
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how do i measure bearing clearances??

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    Senior Member $uperJoe's Avatar
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    Default how do i measure bearing clearances??

    just got all my bottom end parts back from the shop and want to know my exact bearing clearances. both mains and rods. i tried plasti-gage but that seems like a guess at best. all i know is i have more than .002" on one main. that is all i checked with that system.

    what is the procedure to measure the clearance?


    also what should i be looking for as ideal. this is a 460 jet boat application. mild cam and stock heads. probably not over 415 HP and wont rev past 5500RPM unless i air the boat out. i do want to be able to hold 5k RPM for miles at a time however

    thanks in advance
    Joe

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    The most accurate method is to use precision inside and outside mic's to measure the torqued up bearings and the crank. Subtract the difference to get the clearance.

    Plastigage can be used but does not work reliably with rod and main caps that have anti-shuffle (alignment) sleeves. It's almost impossible to get the caps off without effecting the results.

    You should be looking for .0025" on the mains and .0020" on the rods.

    MrE
    Last edited by MrEracer; 11-11-2012 at 06:56 AM.

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    Blown, OHBA Member Wild Hair's Avatar
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    I run mine a bit more than that. 0.003 on the mains and 0.0035 on the rods. Cold idle 75 psi, hot is 45, and 80psi at 6100. Oil moving through the bearings helps pull heat out of the rotating assembly.
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    Senior Member ICECREAMAN's Avatar
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    Spend $400.00 - $500.00 on mics and get proficient using them, which takes a little time. Then it's just math. You should invest in a quality "How to" manual that shows you how the measure your crank and rods, as well as other components. Plasti gauge won't cut it if you want to build a quality motor.
    These books are really well done.
    Reher Morrison Racing Engines

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    Senior Member CNC BLOCKS's Avatar
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    If your going to use a bore gauge use one like a Sunnen bore gauge with floating fingers as the cheap ridgid finger bore gauages and not very accurate when dealing with bearings with eccentricity.


    Ask Mahle/Clevite which is the better gauge to measure bearings with !!

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    Senior Member rocket98's Avatar
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    Joe Here is a good thread from awhile back How to properly check bearing clearance . Hope this helps
    Rick
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    gn7
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    Quote Originally Posted by CNC BLOCKS View Post


    Ask Mahle/Clevite which is the better gauge to measure bearings with !!
    I did call. They said to put your Sunnen bore gauge where the sun's ultra violet rays won't harm it.



    I don't know if this thread is about the best and most expensive way to measure bearing clearances.
    Not EVERYBODY here is making 850 HP from a 350" small block spinning 9500 for hours with 1.5 thou main clearance and 0 WT oil.

    Millions of engines assembled EVERYDAY by the oems, and NOTHING is measured once it leaves its station. When the crank is finished, nobody measures it again. Same with the rods and main bores. Nobody select fits the bearings. MILLIONS of them run for 100,000 miles or more.

    Millions more are assembled by guys in there garage with nothing more than plastigauge. They run a and live just fine.

    So whats the BEST according to YOU and Mahle, is fare from the best for a guy that probably isn't really all that apt at reading a micrometer. Because if he was, I doubt he would have started this thread.

    Know ANYBODY, that asks that question, and doesn't own a mic and bore gauge setup, and is EXPERT at reading one?

    CNC, the measuring device is ONLY as good as the person holding it!

    A suspect a 100.00 bore gauge is well within the requirements of the OP.



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    Last edited by gn7; 11-11-2012 at 11:55 AM.

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    steelcomp was here
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    Quote Originally Posted by gn7 View Post
    I did call. They said to put your Sunnen bore gauge where the sun's ultra violet rays won't harm it.



    I don't know if this thread is about the best and most expensive way to measure bearing clearances.
    Not EVERYBODY here is making 850 HP from a 350" small block spinning 9500 for hours with 1.5 thou main clearance and 0 WT oil.

    Millions of engines assembled EVERYDAY by the oems, and NOTHING is measured once it leaves its station. When the crank is finished, nobody measures it again. Same with the rods and main bores. Nobody select fits the bearings. MILLIONS of them run for 100,000 miles or more.

    Millions more are assembled by guys in there garage with nothing more than plastigauge. They run a and live just fine.

    So whats the BEST according to YOU and Mahle, is fare from the best for a guy that probably isn't really all that apt at reading a micrometer. Because if he was, I doubt he would have started this thread.

    Know ANYBODY, that asks that question, and doesn't own a mic and bore gauge setup, and is EXPERT at reading one?

    CNC, the measuring device is ONLY as good as the person holding it!

    A suspect a 100.00 bore gauge is well within the requirements of the OP.
    No offense Bob, but I'd recommend plasti long before I'd tell someone to waste (yes waste) less than 500.00 on a bore gauge. Cheap bore gauges are just that, and it's not necessarily their accuracy that's an issue, but more, their reliablity and their repeatability. I quit using my -decent- SPI bore gauge that reads in tenths becuase it just wasn't reliable/repeatable. It wasn't cheap, either, but I just couldn't trust it. Frankly, I don't trust dial bore gauges in general. I prefer an inside mic that I know I can trust, and I read that with a C mic. Analog doesn't lie.
    JMO
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    Quote Originally Posted by rocket98 View Post
    Joe Here is a good thread from awhile back How to properly check bearing clearance . Hope this helps
    Rick
    Holy crap!, just read that whole thread, those were good times.
    Sent from my electric web watchin tv thing.

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    gn7
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    Quote Originally Posted by steelcomp View Post
    Frankly, I don't trust dial bore gauges in general. I prefer an inside mic that I know I can trust, and I read that with a C mic. Analog doesn't lie.
    JMO
    I agree. I personally would even consider snap gauges and an outside mic over a cheap bore gauge. Yes, I also perfer a inside/outside mic. But then thats because I didn't even own a bore gauge until a couple years ago, and not all that thrilled either.
    Would I set up a tight clearanced crank with a bore gauge? NO!
    But like I said, there are thousands of engines assembled everyday with less desirable tools. But they aren't trying to run 1.5 on the mains and turn 9500.

    No offense to the OP at all, but what do you think the repeatability would be if you handed him a Starrett inside and outside set?
    Try to keep in mind that the people that are recommending or commenting on what they use, would have never started this thread. Does the OP really need a 500.00 plus bore gauge, or 1000.00 inside out side set up.

    My suggestion if he REALLY wants to know the REAL clearances, would be to haul it all to somebody that has the RIGHT stuff, and he KNOWS they have the knowledge, and have them check it all. But you and I know that makes a few assumptions you and I don't trust either.
    Which to you trust more Steel? YOU and your bore gauge, or the guy at the nearest machine shop?
    Like I said, it all only as good as the person holding the tool.



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    Last edited by gn7; 11-11-2012 at 01:25 PM.

  13. #11
    Senior Member $uperJoe's Avatar
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    Default does my crank need a poish??

    jet boat application

    mains with bearing clearances show

    they are as follows.
    1 .003
    2 .002
    3 .002
    4 .002
    5. 003

    got the rod journals measured.
    i didnt do each rod but each lobe. front to back
    1 .0020
    2 .0027
    3 .0027
    4 .0023
    i want to make sure i have enough clearance to keep the bearing cool with oil and live a long happy life at idle or 5k RPM

  14. #12
    Senior Member CNC BLOCKS's Avatar
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    Quote Originally Posted by gn7 View Post
    I did call. They said to put your Sunnen bore gauge where the sun's ultra violet rays won't harm it.



    I don't know if this thread is about the best and most expensive way to measure bearing clearances.
    Not EVERYBODY here is making 850 HP from a 350" small block spinning 9500 for hours with 1.5 thou main clearance and 0 WT oil.

    Millions of engines assembled EVERYDAY by the oems, and NOTHING is measured once it leaves its station. When the crank is finished, nobody measures it again. Same with the rods and main bores. Nobody select fits the bearings. MILLIONS of them run for 100,000 miles or more.

    Millions more are assembled by guys in there garage with nothing more than plastigauge. They run a and live just fine.

    So whats the BEST according to YOU and Mahle, is fare from the best for a guy that probably isn't really all that apt at reading a micrometer. Because if he was, I doubt he would have started this thread.

    Know ANYBODY, that asks that question, and doesn't own a mic and bore gauge setup, and is EXPERT at reading one?

    CNC, the measuring device is ONLY as good as the person holding it!

    A suspect a 100.00 bore gauge is well within the requirements of the OP.

    I highly doubt you were told this by Mahle/Clveite nice try though. Cheap bore gauges with ridgid fingers are not as accurate as the sunnen bore gauges.

    I would say plastigause is more accurate then some of the cheap bore gauges oth there.

    I have had plenty of bore gauge wars and both of my shops and the sunnen seems to be a much better gauge over the cheap ones. The reason I have to bore gauge wars is the customers are having issues with bearing and I am not.

    I can only imagine what you are using for bore gauges to check bearingsJust saying.

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    gn7
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    Quote Originally Posted by CNC BLOCKS View Post

    I would say plastigause is more accurate then some of the cheap bore gauges oth there.

    I can only imagine what you are using for bore gauges to check bearingsJust saying.
    I use a Stanley 25ft tape from Home Depot asshole!

    I agree, too many bore guages, either cheaply made of ill designed for the task do exist.
    Yea, plastigauge is the shiznit for checking out of round and taper.

    99.9% of us use feeler gauges to lash valves. You can have 5 people lash a set of valves and you get 6 different settings, all of which are wrong.



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    Last edited by gn7; 11-11-2012 at 07:35 PM.

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    steelcomp was here
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    Quote Originally Posted by gn7 View Post
    I agree. I personally would even consider snap gauges and an outside mic over a cheap bore gauge. Yes, I also perfer a inside/outside mic. But then thats because I didn't even own a bore gauge until a couple years ago, and not all that thrilled either.
    Would I set up a tight clearanced crank with a bore gauge? NO!
    But like I said, there are thousands of engines assembled everyday with less desirable tools. But they aren't trying to run 1.5 on the mains and turn 9500.

    No offense to the OP at all, but what do you think the repeatability would be if you handed him a Starrett inside and outside set?
    Try to keep in mind that the people that are recommending or commenting on what they use, would have never started this thread. Does the OP really need a 500.00 plus bore gauge, or 1000.00 inside out side set up.

    My suggestion if he REALLY wants to know the REAL clearances, would be to haul it all to somebody that has the RIGHT stuff, and he KNOWS they have the knowledge, and have them check it all. But you and I know that makes a few assumptions you and I don't trust either.
    Which to you trust more Steel? YOU and your bore gauge, or the guy at the nearest machine shop?Like I said, it all only as good as the person holding the tool.
    Well funny you should ask. I thought I was pretty damn accurate with my dial bore gauge...until I started using the machine shop I use now. You think I'm anal???LOL...
    We were coming up with a .0004 "difference of opinion" on some measurements which led me to hauling all my measuring equipment to the machine shop and finding out why. We measured apples for apples, same time, same journals, same rod bores, etc. Short story shorter, I no longer use my dial bore gauge and bought a Mit ID mic. F that bore gauge. My shop had some discrepancies as well, but it was clear that my bore gauge was lying. I trusted my shop's info enough to question my own, and glad I did.
    As far as the OP goes, this is why I suggest the Plastigage. It doesn't require any real technical "skill" and if someone takes the time to do it carefully and do it correctly...with fresh Plasti...then your advice is sound in that, for most performance clearances (not trying to run .0015 +/- .00005), the Plasti will tell him what he needs to know. I also agree that if he really wants to know what the clearances are accurately, he needs someone to help him with that.
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