Trust Machine Shop On Bearing Clearance or Plastigage?
#1
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Trust Machine Shop On Bearing Clearance or Plastigage?
I am building my first engine (LT1 383) and picked up my block and rotating assembly from the machine shop (well respected performance shop with a lot of experience). They speced the bearings and I have the measured clearance of each individual bearing and not just a general number/range.
Considering that, do you think I should still plastigage them to double check? I had originally planned to, but in thinking about it their measuring tools were clearly superior and they know what they're doing.
Thoughts?
Considering that, do you think I should still plastigage them to double check? I had originally planned to, but in thinking about it their measuring tools were clearly superior and they know what they're doing.
Thoughts?
#2
TECH Addict
I am building my first engine (LT1 383) and picked up my block and rotating assembly from the machine shop (well respected performance shop with a lot of experience). They speced the bearings and I have the measured clearance of each individual bearing and not just a general number/range.
Considering that, do you think I should still plastigage them to double check? I had originally planned to, but in thinking about it their measuring tools were clearly superior and they know what they're doing.
Thoughts?
Considering that, do you think I should still plastigage them to double check? I had originally planned to, but in thinking about it their measuring tools were clearly superior and they know what they're doing.
Thoughts?
If you do want to double check then use bore gauges and a micrometer that reads to the 10 thousands of an inch.
#4
TECH Resident
IMHO...
Bore gauges and micrometers are what is best(with the proper resolution), but plastigauge is better than nothing to do a double check(....and as with a bore gauge, you must use it properly). After all, we are all human and we do make mistakes from time to time. Better to double check now than find out later with engine trouble.
For what it's worth, the GM factory F-body manual(1996) specifically states(page 6A3B-24) to use plastigauge to check the main/rod bearing clearances. It does not mention anything about using a bore gauge. They didn't call it plastigauge though, they called it "gaging plastic". So...for them not to even mention bore gauge tells me that there is validity in the measurement method.
I used plastigauge to select the new bearing shells when I replaced the rod and main bearings in my LT1. I must have done something right as I still have 25-30psi at idle 3+ years later(and many, many track passes). I also had no trouble with my crank being out of round/spec either(I verified that with a micrometer).
Plastigauge is something I would not expect a performance engine shop to use as the defacto measurement standard for checking clearances. However, it does have it's place as being useful for those of us who do not build engines on a day to day basis.
Bore gauges and micrometers are what is best(with the proper resolution), but plastigauge is better than nothing to do a double check(....and as with a bore gauge, you must use it properly). After all, we are all human and we do make mistakes from time to time. Better to double check now than find out later with engine trouble.
For what it's worth, the GM factory F-body manual(1996) specifically states(page 6A3B-24) to use plastigauge to check the main/rod bearing clearances. It does not mention anything about using a bore gauge. They didn't call it plastigauge though, they called it "gaging plastic". So...for them not to even mention bore gauge tells me that there is validity in the measurement method.
I used plastigauge to select the new bearing shells when I replaced the rod and main bearings in my LT1. I must have done something right as I still have 25-30psi at idle 3+ years later(and many, many track passes). I also had no trouble with my crank being out of round/spec either(I verified that with a micrometer).
Plastigauge is something I would not expect a performance engine shop to use as the defacto measurement standard for checking clearances. However, it does have it's place as being useful for those of us who do not build engines on a day to day basis.
Last edited by ACE1252; 02-24-2015 at 12:40 AM.
#5
TECH Resident
Just for reference, here are a few threads on what I went through a few years ago when working on the bearing replacement for my LT1...cam, rod, and mains(and why I replaced them).
http://www.camaroz28.com/forums/lt1-...ctures-713070/
http://www.camaroz28.com/forums/lt1-...arings-746672/
http://www.camaroz28.com/forums/lt1-...arings-749300/
http://www.camaroz28.com/forums/lt1-...ctures-713070/
http://www.camaroz28.com/forums/lt1-...arings-746672/
http://www.camaroz28.com/forums/lt1-...arings-749300/
#6
TECH Addict
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I think this poster means tenths of an inch (0.0001") not to be confused with 10 thousands of an inch (0.010"). digital mics will be preferred, a standard analog can be a little bit up to interpretation when it comes to reading in such fine measurements in regards to a mic.
#7
TECH Fanatic
If you are assembling the motor I would check and compare it to their measurements. And I would use plastigage at the very least. Just for the piece of mind.
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#8
TECH Addict
I think this poster means tenths of an inch (0.0001") not to be confused with 10 thousands of an inch (0.010"). digital mics will be preferred, a standard analog can be a little bit up to interpretation when it comes to reading in such fine measurements in regards to a mic.
Last edited by hrcslam; 02-24-2015 at 07:50 PM.
#9
TECH Addict
IMHO...
Bore gauges and micrometers are what is best(with the proper resolution), but plastigauge is better than nothing to do a double check(....and as with a bore gauge, you must use it properly). After all, we are all human and we do make mistakes from time to time. Better to double check now than find out later with engine trouble.
For what it's worth, the GM factory F-body manual(1996) specifically states(page 6A3B-24) to use plastigauge to check the main/rod bearing clearances. It does not mention anything about using a bore gauge. They didn't call it plastigauge though, they called it "gaging plastic". So...for them not to even mention bore gauge tells me that there is validity in the measurement method.
I used plastigauge to select the new bearing shells when I replaced the rod and main bearings in my LT1. I must have done something right as I still have 25-30psi at idle 3+ years later(and many, many track passes). I also had no trouble with my crank being out of round/spec either(I verified that with a micrometer).
Plastigauge is something I would not expect a performance engine shop to use as the defacto measurement standard for checking clearances. However, it does have it's place as being useful for those of us who do not build engines on a day to day basis.
Bore gauges and micrometers are what is best(with the proper resolution), but plastigauge is better than nothing to do a double check(....and as with a bore gauge, you must use it properly). After all, we are all human and we do make mistakes from time to time. Better to double check now than find out later with engine trouble.
For what it's worth, the GM factory F-body manual(1996) specifically states(page 6A3B-24) to use plastigauge to check the main/rod bearing clearances. It does not mention anything about using a bore gauge. They didn't call it plastigauge though, they called it "gaging plastic". So...for them not to even mention bore gauge tells me that there is validity in the measurement method.
I used plastigauge to select the new bearing shells when I replaced the rod and main bearings in my LT1. I must have done something right as I still have 25-30psi at idle 3+ years later(and many, many track passes). I also had no trouble with my crank being out of round/spec either(I verified that with a micrometer).
Plastigauge is something I would not expect a performance engine shop to use as the defacto measurement standard for checking clearances. However, it does have it's place as being useful for those of us who do not build engines on a day to day basis.
I used both the plastigage and bore Guage with a Mic on my build. I went with the bore guages for my official measurements. For a stock rebuild, I wouldn't bother with bore guages.
#12
Village Troll
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OP, if you are on the east coast near Maryland I can recommend a shop that has done many LTx/LSx platforms.
#13
TECH Fanatic
Exactomundo. Machine shops should be chosen or avoided on their reputation. If you are going to take caps off and measure you might as well build the thing yourself.
OP, if you are on the east coast near Maryland I can recommend a shop that has done many LTx/LSx platforms.
OP, if you are on the east coast near Maryland I can recommend a shop that has done many LTx/LSx platforms.
#17
Village Troll
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Last edited by SS RRR; 02-26-2015 at 06:52 AM.
#18
TECH Addict
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I meant to the ten thousands of an inch. Like 0.000X". A tenth of an inch is 0.X". What you typed was 10 thousands inch or 0.010", also known a hundredths of an inch. Versus to the thousandth of an inch which is 0.00X". If someone says 25 ten thousandths inch they are saying 0.0025". If they say 25 thousandths inch they are saying 0.025". Make sense? Bearings should have clearances to the 10 thousandths of an inch.
Since this topic refers to automotive machine shops and machinist inspection tools, machine shop nomenclature is what takes presidence.
#20
TECH Addict
Tenths of thousandths of an inch, I forgot to include the "of thousands" portion. In machining a tenth is short hand for this, almost never will anyone refer to a tenth as 0.100" unless they've not been in the environment long, and almost as unlikely will anyone call it by its longer name. I've yet to hear anyone refer to 0.0001" as 10 thousandths of an inch. If someone called out a true position of 10 thousandths on a hole position, you'd think you had a pretty wide open geometric tolerance, not butt pucker tight 1 tenth. You might be thinking of 1/10 of a thousandths of an inch (aka 1 tenth to a machinist/engineer/drafter).
Since this topic refers to automotive machine shops and machinist inspection tools, machine shop nomenclature is what takes presidence.
Since this topic refers to automotive machine shops and machinist inspection tools, machine shop nomenclature is what takes presidence.