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Discussion Starter #1
I have read a few of the threads on measuring bearing clearances.
I have read that some prefer using inside mic's with out side mic's, rather than a dial bore gauge.
What type and brand of inside mic, would you use, a straight style( for lack of a better word), a telescoping snap gauge, a tri point mic or a mic with the outward facing points( again for a lack of a better word)?













 

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The advantage a dial bore guage has is that you can set it to the outside micrometer reading for a journal, the use to not only check bearing clearance, but also taper and how far out of round the bearing is in the housing.

Many, many years ago, before I bought a dial bore gauge, I used snap gauges. In my opinion it's quite a bit more tedious, since you have to carefully set it, pull it out and measure with the outside mic, then go back and double check, or check another angle, etc. I don't think you will be quite as accurate, but if you are careful, you should be able to use them to verify clearance.
 

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Like Barry said, they all work, and they all can be pretty accurate. Its all in the user. I can get pretty good readings with snap gauges, but its a PITA, and time consuming.
Inside mics work, but I never use the number on the mic, I check it against the mic I used on the crank and compare the two to get the clearance.
I still actually prefer them for crank work, but the bore is small and narrow, and frankly I don't get to hung up in the "side" measurement. It is what it is. I only care about the vertical clearance, and the front to back saddle bore measurement before the bearing went in the block to check for bore taper.

For cylinders, like Barry said, you can check the bore top to bottom relatively quickly with a bore gauge. Again, I check it against the outside mic, or a standard I measured with the outside mic.
However, if the block was honed with a deck plate, and you measure it with the heads off, you can get numbers that can be down right scary. Specially if you spin it to check roundness, Because it won't be, specially up near the deck.



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As mentioned..

I've found the quickest/easiest way is use the "outside" standard Mic, set at the journal size to "zero" the dial bore gage. Measure the journal, "lock" the mic and carefully set it up in a bench vise with padding, then "zero" the bore gage using the "just measured" and locked mic...
Once zeroed, measure the bearing ID, and you'll see the clearance directly on the dial.... I would add that you "plan ahead" when measuring the mains so that you have room to measure without other caps being in the way... AND, a BIG and, be sure to fully support the big end of the rods while torquing/untorquing them... Rods WILL twist if not properly supported... I use a set of custom made aluminum "jaws" in my Kurt mill vise and leave just enough room to get to the bolts/nuts...
Ray
PS Hal, if you're using NEW ARP bolts be sure to measure, and RECORD, the "new" length before you even start. List the bolts, and the rod numbers, as well as "tang" side.... Oh, and remember to use the .0001 readings on the back side of the mic barrel... Yes, it's THAT critical.... If those bolts are ever reused, you'll need those numbers to assure they haven't "grown"...... 2nd OH yeah, wear plastic gloves while handling the ARP bolts...
 

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Micrometers are all about the hands. If your a big brute type person and you can't get the "feel" correctly, you may end up with big/little readings.
Practice is your friend !
 

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steelcomp was here
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The tri-mic you have pictured is awesome for lifter bores.
Telescoping gauges, IMO, are last choice for places where you can't get an ID mic.
Bore gauges can get you in trouble if you're not spending the coin on a very good one. I have a fairly expensive one and it's caused me problems. I've since put it away and now use inside mics and C mics. I use the inside mic sort of like a telescoping gauge. I set it, then measure it with the C mic. My inside mic is very similar to the second on in your pics. Dial bore gauge is faster, but IMO you shouldn't be in a hurry doing this sort of thing.
ID mics and C mics are pretty fool proof but as mentioned, they take practice and feel. They are also very temperature sensitive if you're measuring tenths or less.
Choose your poison.
 

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Ambient temperature changes...I could believe what a temp swing does to parts and what the mics show :shock:
 

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steelcomp was here
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Ambient temperature changes...I could believe what a temp swing does to parts and what the mics show :shock:
Just hold a mic in your hand for more than a minute and then re-check it on your standard. You do that frequently, right? Check your mics with the standards? :)bulb
 

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Like Barry said, they all work, and they all can be pretty accurate. Its all in the user. I can get pretty good readings with snap gauges, but its a PITA, and time consuming.
Inside mics work, but I never use the number on the mic, I check it against the mic I used on the crank and compare the two to get the clearance.
I still actually prefer them for crank work, but the bore is small and narrow, and frankly I don't get to hung up in the "side" measurement. It is what it is. I only care about the vertical clearance, and the front to back saddle bore measurement before the bearing went in the block to check for bore taper.

For cylinders, like Barry said, you can check the bore top to bottom relatively quickly with a bore gauge. Again, I check it against the outside mic, or a standard I measured with the outside mic.
However, if the block was honed with a deck plate, and you measure it with the heads off, you can get numbers that can be down right scary. Specially if you spin it to check roundness, Because it won't be, specially up near the deck.
Spot on IMHO.... I'd invest in dial bore gauges if I built a lot of motors or was doing it for $$$. For the number of motors I build, T gauges/inside mics are fine...
 

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The used parts hunt

When I'm out on the hunt for blocks, cranks, etc a good tool to have is a quality pair of calipers. Always good to check the claimed sizes for yourself before dropping any coin. They will give you a quick reference. Kinda like "measure twice-cut once" rule of thumb. I'm guessing most all wrenchers on this site propably have a pair or two in their boxes.
 

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I have a dial bore guage, snap gauges, mics & stuff, but for the novice, or just to double check you work its hard to beat the old plastiguage. One thing you can say for it, it removes all of the variables and will show taper.
 

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I have to disagree with plastiguage. I have been lied to too many times to use that stuff. Old guage gives terrible readings. Even if you buy a new stick it can be old stock and worthless. I guess if you have
nothing else to use. But if that's the case you better really trust your machine shop.

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I have to disagree with plastiguage. I have been lied to too many times to use that stuff. Old guage gives terrible readings. Even if you buy a new stick it can be old stock and worthless. I guess if you have
nothing else to use. But if that's the case you better really trust your machine shop.

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I haven't used it in yrs, but used to and never had a problem. Unless its changed I don't see the issue. I'm not saying to just use plastiguage. But I don't see the problem with using it to double check your work just to see if it agrees with your measurements.
 

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Discussion Starter #16
I've found the quickest/easiest way is use the "outside" standard Mic, set at the journal size to "zero" the dial bore gage. Measure the journal, "lock" the mic and carefully set it up in a bench vise with padding, then "zero" the bore gage using the "just measured" and locked mic...
Once zeroed, measure the bearing ID, and you'll see the clearance directly on the dial.... I would add that you "plan ahead" when measuring the mains so that you have room to measure without other caps being in the way... AND, a BIG and, be sure to fully support the big end of the rods while torquing/untorquing them... Rods WILL twist if not properly supported... I use a set of custom made aluminum "jaws" in my Kurt mill vise and leave just enough room to get to the bolts/nuts...
Ray
PS Hal, if you're using NEW ARP bolts be sure to measure, and RECORD, the "new" length before you even start. List the bolts, and the rod numbers, as well as "tang" side.... Oh, and remember to use the .0001 readings on the back side of the mic barrel... Yes, it's THAT critical.... If those bolts are ever reused, you'll need those numbers to assure they haven't "grown"...... 2nd OH yeah, wear plastic gloves while handling the ARP bolts...
Ray, why plastic gloves for handeling the arp bolts?
 

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Discussion Starter #17
The tri-mic you have pictured is awesome for lifter bores.
Telescoping gauges, IMO, are last choice for places where you can't get an ID mic.
Bore gauges can get you in trouble if you're not spending the coin on a very good one. I have a fairly expensive one and it's caused me problems. I've since put it away and now use inside mics and C mics. I use the inside mic sort of like a telescoping gauge. I set it, then measure it with the C mic. My inside mic is very similar to the second on in your pics. Dial bore gauge is faster, but IMO you shouldn't be in a hurry doing this sort of thing.
ID mics and C mics are pretty fool proof but as mentioned, they take practice and feel. They are also very temperature sensitive if you're measuring tenths or less.
Choose your poison.
Scott, one reason i asked about the tri mic was what I saw in this engine building series on youtube. This guy has a 27 video series on building a bbc, and used a tri mic for measuring bearing clearances. The guy is a bit of a goof, but his vids are intresting.
Part 7 Measure, Order & Install Main Bearings For The Big Block Chevy - YouTube
 

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Moisture/acids...

Ray, why plastic gloves for handeling the arp bolts?
Hal, it's the acids and moisture in our hands/finger tips that CAN pollute the metals... The same can be said for handling bearing shells... Depending on the ARP type, moisture CAN be a big no no....

Ray
 

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Scott, one reason i asked about the tri mic was what I saw in this engine building series on youtube. This guy has a 27 video series on building a bbc, and used a tri mic for measuring bearing clearances. The guy is a bit of a goof, but his vids are intresting.
Part 7 Measure, Order & Install Main Bearings For The Big Block Chevy - YouTube
Bearing shells are not round, and using a tri-finger mic like that on main and rod bearings will get you in big trouble real fast. It's a very cool tool but it needs to be used in it's proper application.
 

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Hal, it's the acids and moisture in our hands/finger tips that CAN pollute the metals... The same can be said for handling bearing shells... Depending on the ARP type, moisture CAN be a big no no....

Ray
Only bolt you really have to worry about is the L19 bolt. Having said that, everybody's PH is different. We had a guy at one shop that we just flat would not allow to touch any bare steel. In minutes, his finger prints were turning brown. Some people are just like that.
 
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