Unsure what to do with 0.0020" Main Clearance
Moderator: Team
Re: Unsure what to do with 0.0020" Main Clearance
I can't imagine why you would need to re-nitride the crank only taking a thou off. Seems ridiculous.
Pullin' for Christ
Re: Unsure what to do with 0.0020" Main Clearance
I knew a guy who raced 351C's back in the day with stock rods. As I said... BACK IN THE DAY before everyone was using aftermarket stuff. He kept wiping out rod bearings. His theory, was that at high rpm, the cap was stretching, pulling the sides of the rod in, and the bearing halves were squeegee-ing the oil off the crank. He started having the rods machined wider at the parting line, and no more spun bearings.
It's 2nd hand info, as it wasn't me... but sounded reasonable!
Re: Unsure what to do with 0.0020" Main Clearance
That's what I was doing. Measuring the crank, locking the mic... then zeroing the bore gauge with the mic. After the bore gauge was zero'd on the crank measurement, it measures the clearance directly when you place it in the bearing.BigBlocksOnTop2 wrote: ↑Sun Mar 29, 2020 7:01 pm Are you setting the dial bore gauge to zero on the journal (using a mic) and then measuring the corresponding bearing? May make you feel a little better....
I had mentioned that I locked the mic while it was still on the crank, then pulled it off to take the reading/set the gauge... and someone said that would change the reading... so I might do some comparisons, and see if it holds merit with my mics.
Re: Unsure what to do with 0.0020" Main Clearance
Good idean2omike wrote: ↑Sun Mar 29, 2020 10:19 pmThat's what I was doing. Measuring the crank, locking the mic... then zeroing the bore gauge with the mic. After the bore gauge was zero'd on the crank measurement, it measures the clearance directly when you place it in the bearing.BigBlocksOnTop2 wrote: ↑Sun Mar 29, 2020 7:01 pm Are you setting the dial bore gauge to zero on the journal (using a mic) and then measuring the corresponding bearing? May make you feel a little better....
I had mentioned that I locked the mic while it was still on the crank, then pulled it off to take the reading/set the gauge... and someone said that would change the reading... so I might do some comparisons, and see if it holds merit with my mics.
Racing a NA NHRA stocker should be mandatory before any posting.
-
- Expert
- Posts: 537
- Joined: Mon Dec 12, 2016 3:37 pm
- Location:
Re: Unsure what to do with 0.0020" Main Clearance
what do you have for clearance with those Oliver rods Mike with the same x bearing?
-
- New Member
- Posts: 7
- Joined: Sun Mar 29, 2020 9:35 pm
- Location: Calanazi, CA
Re: Unsure what to do with 0.0020" Main Clearance
I'm in shock on some of the replies to your post. First, other than the plasti-gauge, what are you checking the bearing clearance with? Some have mentioned using the Sunnen dial bore gauge, or a bore gauge of similar fashion. While the "bore gauge" is fairly accurate it not, repeat, not the definitive say on clearance. Here is the dilemma.... the carbide stylus, due to spring pressure, plus the feet will dig into the bearing. If you turn the spring tension down low enough to not drag the stylus, it will not center. Secondly, would you check a curved surface with a standard mic? Due to the dial bore gauge (the Sunnen model) being used repeatedly in a 4"+ bore, the stylus has worn itself almost flat, the line bore gauge would not be as inaccurate. I realize this equates to around .0003 to .0004, however if you had an extra .0004 clearance, this post wouldn't exist.
Increasing housing bore diameter is a dangerous scenario, in today's boosted or nitrous world.... main cap bounce is a very real issue.If you know your math (Pi=3.1415) if you were to open up the housing bore .0005, it should increase bearing clearance approx .0015, taking into account the housing bore is within .0002 @ any position with no shadows on the parting line or cap. If you were on the tight, a few more tenths in the housing bore clearance shouldn't present a problem. Stay away from max diameter whenever possible, hearty bearing crush is your friend. Also, ACL offers bearings in .009, and .011 undersizes to dial in your clearance when the crankshaft has been turned .010. I am unaware of any manufacturer that offers this in anything other than .010, however there may be an offering somewhere on the planet.
I cannot begin to fathom anyone sanding bearings for clearance..... this is wrong on so many levels, I don't know where to start. First, you are changing concentricity, meaning the bearing is no longer centered to the axis of the crank. Sure, there's more clearance, but what effect is having on the rest of the bearing? No one on this forum has the ability to answer the question. Taper, oil pressure bleed off, I could go on and on.
Re-grinding? If I could find a shop that could take .0005 off, you have my business for the rest of my natural life. The shear nature of the process dictates it's an impossibility. You are attempting to take .00025 off with a consumable, the grinding stone. Let's say you could for arguments sake, and managed to get the .00025 off the number 1 main. By the time you got the number 5 main, the rest of it is going to be a mess if we're using .0001. The slightest pressure indifference on the steady rest is going to have you chasing your tail, ultimately working into a bigger problem. I would love to run a profilometer over those journals.... it would look like the Swiss Alps.
Let's talk heat. How much additional clearance would you calculate the clearances open to at operating temperature? Surely we have all honed blocks to where is you could not touch the cylinder. Letting it cool, you are now say .0007 to .001 tight when you were to size previously.... The crankshaft is a much denser alloy, and would expand somewhat, but nothing like cast iron would. How about Aluminum? So is it a half? 3 tenths? I can tell you approximately it is around .0005 to .0007 depending on. How do I know this? We heated blocks to operating temperature and measured clearance. We also ran 190 degree water thru the block while honing to final size.
.002 clearance will be absolutely fine. Ever looked at the back of a bearing on freshen up? The hone marks are impregnated in the steel backing, giving it a couple two three tenths.
Enough ranting, best of luck on your build.
Increasing housing bore diameter is a dangerous scenario, in today's boosted or nitrous world.... main cap bounce is a very real issue.If you know your math (Pi=3.1415) if you were to open up the housing bore .0005, it should increase bearing clearance approx .0015, taking into account the housing bore is within .0002 @ any position with no shadows on the parting line or cap. If you were on the tight, a few more tenths in the housing bore clearance shouldn't present a problem. Stay away from max diameter whenever possible, hearty bearing crush is your friend. Also, ACL offers bearings in .009, and .011 undersizes to dial in your clearance when the crankshaft has been turned .010. I am unaware of any manufacturer that offers this in anything other than .010, however there may be an offering somewhere on the planet.
I cannot begin to fathom anyone sanding bearings for clearance..... this is wrong on so many levels, I don't know where to start. First, you are changing concentricity, meaning the bearing is no longer centered to the axis of the crank. Sure, there's more clearance, but what effect is having on the rest of the bearing? No one on this forum has the ability to answer the question. Taper, oil pressure bleed off, I could go on and on.
Re-grinding? If I could find a shop that could take .0005 off, you have my business for the rest of my natural life. The shear nature of the process dictates it's an impossibility. You are attempting to take .00025 off with a consumable, the grinding stone. Let's say you could for arguments sake, and managed to get the .00025 off the number 1 main. By the time you got the number 5 main, the rest of it is going to be a mess if we're using .0001. The slightest pressure indifference on the steady rest is going to have you chasing your tail, ultimately working into a bigger problem. I would love to run a profilometer over those journals.... it would look like the Swiss Alps.
Let's talk heat. How much additional clearance would you calculate the clearances open to at operating temperature? Surely we have all honed blocks to where is you could not touch the cylinder. Letting it cool, you are now say .0007 to .001 tight when you were to size previously.... The crankshaft is a much denser alloy, and would expand somewhat, but nothing like cast iron would. How about Aluminum? So is it a half? 3 tenths? I can tell you approximately it is around .0005 to .0007 depending on. How do I know this? We heated blocks to operating temperature and measured clearance. We also ran 190 degree water thru the block while honing to final size.
.002 clearance will be absolutely fine. Ever looked at the back of a bearing on freshen up? The hone marks are impregnated in the steel backing, giving it a couple two three tenths.
Enough ranting, best of luck on your build.
You do not have the required permissions to view the files attached to this post.
Re: Unsure what to do with 0.0020" Main Clearance
Only has to be as good as what your working with.
Taking a file to a bearing......? Sometimes you'd be an idiot, other times that would be an improvement, and you'd be an idiot NOt to do it.
Checking the bearing thickness and housings and shaft sizes carefully, and checking the crush.... you will find out what's going on, and where the problem lies. probably the housing is too small, or shaft too big, so, fix that, whichever it may be.
Re: Unsure what to do with 0.0020" Main Clearance
And all these measured numbers being mentioned are the high spots that are being measured. How many tenths more do the low spots add [ hills & valleys ] add to the measured dimension? Was it Shakespeare who said, 'Much ado about nothing...'
-
- Guru
- Posts: 1649
- Joined: Tue Mar 06, 2007 7:23 pm
- Location: San Tan Valley, AZ
- Contact:
Re: Unsure what to do with 0.0020" Main Clearance
I don't know....we all get to measure the reason some guys drive monster trucks on the street.....
Re: Unsure what to do with 0.0020" Main Clearance
Nothing wrong with opening up the housing bores .0005 as long as there within spec. If you try to run every hosing bore on the absolute small end, you will at some point find bearings that the sides will try to close in on.BabyFinster wrote: ↑Sun Mar 29, 2020 11:35 pm I'm in shock on some of the replies to your post. First, other than the plasti-gauge, what are you checking the bearing clearance with? Some have mentioned using the Sunnen dial bore gauge, or a bore gauge of similar fashion. While the "bore gauge" is fairly accurate it not, repeat, not the definitive say on clearance. Here is the dilemma.... the carbide stylus, due to spring pressure, plus the feet will dig into the bearing. If you turn the spring tension down low enough to not drag the stylus, it will not center. Secondly, would you check a curved surface with a standard mic? Due to the dial bore gauge (the Sunnen model) being used repeatedly in a 4"+ bore, the stylus has worn itself almost flat, the line bore gauge would not be as inaccurate. I realize this equates to around .0003 to .0004, however if you had an extra .0004 clearance, this post wouldn't exist.
Increasing housing bore diameter is a dangerous scenario, in today's boosted or nitrous world.... main cap bounce is a very real issue.If you know your math (Pi=3.1415) if you were to open up the housing bore .0005, it should increase bearing clearance approx .0015, taking into account the housing bore is within .0002 @ any position with no shadows on the parting line or cap. If you were on the tight, a few more tenths in the housing bore clearance shouldn't present a problem. Stay away from max diameter whenever possible, hearty bearing crush is your friend. Also, ACL offers bearings in .009, and .011 undersizes to dial in your clearance when the crankshaft has been turned .010. I am unaware of any manufacturer that offers this in anything other than .010, however there may be an offering somewhere on the planet.
I cannot begin to fathom anyone sanding bearings for clearance..... this is wrong on so many levels, I don't know where to start. First, you are changing concentricity, meaning the bearing is no longer centered to the axis of the crank. Sure, there's more clearance, but what effect is having on the rest of the bearing? No one on this forum has the ability to answer the question. Taper, oil pressure bleed off, I could go on and on.
Re-grinding? If I could find a shop that could take .0005 off, you have my business for the rest of my natural life. The shear nature of the process dictates it's an impossibility. You are attempting to take .00025 off with a consumable, the grinding stone. Let's say you could for arguments sake, and managed to get the .00025 off the number 1 main. By the time you got the number 5 main, the rest of it is going to be a mess if we're using .0001. The slightest pressure indifference on the steady rest is going to have you chasing your tail, ultimately working into a bigger problem. I would love to run a profilometer over those journals.... it would look like the Swiss Alps.
Let's talk heat. How much additional clearance would you calculate the clearances open to at operating temperature? Surely we have all honed blocks to where is you could not touch the cylinder. Letting it cool, you are now say .0007 to .001 tight when you were to size previously.... The crankshaft is a much denser alloy, and would expand somewhat, but nothing like cast iron would. How about Aluminum? So is it a half? 3 tenths? I can tell you approximately it is around .0005 to .0007 depending on. How do I know this? We heated blocks to operating temperature and measured clearance. We also ran 190 degree water thru the block while honing to final size.
.002 clearance will be absolutely fine. Ever looked at the back of a bearing on freshen up? The hone marks are impregnated in the steel backing, giving it a couple two three tenths.
Enough ranting, best of luck on your build. baby finster.jpg
Tightening up the hosing bores .0005 will not tighten up the vertical clearance .0015. It will be closer to .0005. Don’t know how many blocks you have align honed but I’m guessing probably very few.
Re: Unsure what to do with 0.0020" Main Clearance
To paraphrase:
"Not everything that can be counted (measured) counts, and not everything that counts can be counted (measured)."
- Albert Einstein (1879-1955)
"Not everything that can be counted (measured) counts, and not everything that counts can be counted (measured)."
- Albert Einstein (1879-1955)
Re: Unsure what to do with 0.0020" Main Clearance
Yup, that’s why the bearing manufacturers give a max,, it will still give enough crush.houser45 wrote: ↑Mon Mar 30, 2020 8:01 amNothing wrong with opening up the housing bores .0005 as long as there within spec. If you try to run every hosing bore on the absolute small end, you will at some point find bearings that the sides will try to close in on.BabyFinster wrote: ↑Sun Mar 29, 2020 11:35 pm I'm in shock on some of the replies to your post. First, other than the plasti-gauge, what are you checking the bearing clearance with? Some have mentioned using the Sunnen dial bore gauge, or a bore gauge of similar fashion. While the "bore gauge" is fairly accurate it not, repeat, not the definitive say on clearance. Here is the dilemma.... the carbide stylus, due to spring pressure, plus the feet will dig into the bearing. If you turn the spring tension down low enough to not drag the stylus, it will not center. Secondly, would you check a curved surface with a standard mic? Due to the dial bore gauge (the Sunnen model) being used repeatedly in a 4"+ bore, the stylus has worn itself almost flat, the line bore gauge would not be as inaccurate. I realize this equates to around .0003 to .0004, however if you had an extra .0004 clearance, this post wouldn't exist.
Increasing housing bore diameter is a dangerous scenario, in today's boosted or nitrous world.... main cap bounce is a very real issue.If you know your math (Pi=3.1415) if you were to open up the housing bore .0005, it should increase bearing clearance approx .0015, taking into account the housing bore is within .0002 @ any position with no shadows on the parting line or cap. If you were on the tight, a few more tenths in the housing bore clearance shouldn't present a problem. Stay away from max diameter whenever possible, hearty bearing crush is your friend. Also, ACL offers bearings in .009, and .011 undersizes to dial in your clearance when the crankshaft has been turned .010. I am unaware of any manufacturer that offers this in anything other than .010, however there may be an offering somewhere on the planet.
I cannot begin to fathom anyone sanding bearings for clearance..... this is wrong on so many levels, I don't know where to start. First, you are changing concentricity, meaning the bearing is no longer centered to the axis of the crank. Sure, there's more clearance, but what effect is having on the rest of the bearing? No one on this forum has the ability to answer the question. Taper, oil pressure bleed off, I could go on and on.
Re-grinding? If I could find a shop that could take .0005 off, you have my business for the rest of my natural life. The shear nature of the process dictates it's an impossibility. You are attempting to take .00025 off with a consumable, the grinding stone. Let's say you could for arguments sake, and managed to get the .00025 off the number 1 main. By the time you got the number 5 main, the rest of it is going to be a mess if we're using .0001. The slightest pressure indifference on the steady rest is going to have you chasing your tail, ultimately working into a bigger problem. I would love to run a profilometer over those journals.... it would look like the Swiss Alps.
Let's talk heat. How much additional clearance would you calculate the clearances open to at operating temperature? Surely we have all honed blocks to where is you could not touch the cylinder. Letting it cool, you are now say .0007 to .001 tight when you were to size previously.... The crankshaft is a much denser alloy, and would expand somewhat, but nothing like cast iron would. How about Aluminum? So is it a half? 3 tenths? I can tell you approximately it is around .0005 to .0007 depending on. How do I know this? We heated blocks to operating temperature and measured clearance. We also ran 190 degree water thru the block while honing to final size.
.002 clearance will be absolutely fine. Ever looked at the back of a bearing on freshen up? The hone marks are impregnated in the steel backing, giving it a couple two three tenths.
Enough ranting, best of luck on your build. baby finster.jpg
Tightening up the hosing bores .0005 will not tighten up the vertical clearance .0015. It will be closer to .0005. Don’t know how many blocks you have align honed but I’m guessing probably very few.
Yet some on here are more than willing to hand sand the backside, to remove concentricity and crush... before going to a concentric housing bore that’s within recommended specs
-
- New Member
- Posts: 7
- Joined: Sun Mar 29, 2020 9:35 pm
- Location: Calanazi, CA
Re: Unsure what to do with 0.0020" Main Clearance
houser45 wrote: ↑Mon Mar 30, 2020 8:01 amNothing wrong with opening up the housing bores .0005 as long as there within spec. If you try to run every hosing bore on the absolute small end, you will at some point find bearings that the sides will try to close in on.BabyFinster wrote: ↑Sun Mar 29, 2020 11:35 pm I'm in shock on some of the replies to your post. First, other than the plasti-gauge, what are you checking the bearing clearance with? Some have mentioned using the Sunnen dial bore gauge, or a bore gauge of similar fashion. While the "bore gauge" is fairly accurate it not, repeat, not the definitive say on clearance. Here is the dilemma.... the carbide stylus, due to spring pressure, plus the feet will dig into the bearing. If you turn the spring tension down low enough to not drag the stylus, it will not center. Secondly, would you check a curved surface with a standard mic? Due to the dial bore gauge (the Sunnen model) being used repeatedly in a 4"+ bore, the stylus has worn itself almost flat, the line bore gauge would not be as inaccurate. I realize this equates to around .0003 to .0004, however if you had an extra .0004 clearance, this post wouldn't exist.
Increasing housing bore diameter is a dangerous scenario, in today's boosted or nitrous world.... main cap bounce is a very real issue.If you know your math (Pi=3.1415) if you were to open up the housing bore .0005, it should increase bearing clearance approx .0015, taking into account the housing bore is within .0002 @ any position with no shadows on the parting line or cap. If you were on the tight, a few more tenths in the housing bore clearance shouldn't present a problem. Stay away from max diameter whenever possible, hearty bearing crush is your friend. Also, ACL offers bearings in .009, and .011 undersizes to dial in your clearance when the crankshaft has been turned .010. I am unaware of any manufacturer that offers this in anything other than .010, however there may be an offering somewhere on the planet.
I cannot begin to fathom anyone sanding bearings for clearance..... this is wrong on so many levels, I don't know where to start. First, you are changing concentricity, meaning the bearing is no longer centered to the axis of the crank. Sure, there's more clearance, but what effect is having on the rest of the bearing? No one on this forum has the ability to answer the question. Taper, oil pressure bleed off, I could go on and on.
Re-grinding? If I could find a shop that could take .0005 off, you have my business for the rest of my natural life. The shear nature of the process dictates it's an impossibility. You are attempting to take .00025 off with a consumable, the grinding stone. Let's say you could for arguments sake, and managed to get the .00025 off the number 1 main. By the time you got the number 5 main, the rest of it is going to be a mess if we're using .0001. The slightest pressure indifference on the steady rest is going to have you chasing your tail, ultimately working into a bigger problem. I would love to run a profilometer over those journals.... it would look like the Swiss Alps.
Let's talk heat. How much additional clearance would you calculate the clearances open to at operating temperature? Surely we have all honed blocks to where is you could not touch the cylinder. Letting it cool, you are now say .0007 to .001 tight when you were to size previously.... The crankshaft is a much denser alloy, and would expand somewhat, but nothing like cast iron would. How about Aluminum? So is it a half? 3 tenths? I can tell you approximately it is around .0005 to .0007 depending on. How do I know this? We heated blocks to operating temperature and measured clearance. We also ran 190 degree water thru the block while honing to final size.
.002 clearance will be absolutely fine. Ever looked at the back of a bearing on freshen up? The hone marks are impregnated in the steel backing, giving it a couple two three tenths.
Enough ranting, best of luck on your build. baby finster.jpg
Tightening up the hosing bores .0005 will not tighten up the vertical clearance .0015. It will be closer to .0005. Don’t know how many blocks you have align honed but I’m guessing probably very few.
You didn't reference my statement correctly. I said increasing "a few more tenths in the housing bore clearance shouldn't present a problem."As for your statement on housing bore dimension... I tried to keep it simplistic and again said approximately... So in layman's terms.. Bearing "crush" or whatever you want to call it, is actually stored energy, increasing the housing bore dimension will decrease this, of course. Pi is still a constant, however the expansion of the bearing itself will follow the constant with some being shown in the bearing clearance. If you would like, I can explain the design of the Sunnen line hone mandrel... why the feet are offset from center, effects of stone pressure and overstroke... I don't know your resume', as neither you do mine, but I can assure you I have been at this for almost 40 years at a level a very small percentage could survive in. I'm now retired, and joined this forum to A: maybe pass on some of that 35+ years of experience, and B: Learn something for myself, there are some brilliant individuals on here.houser45 wrote: ↑Mon Mar 30, 2020 8:01 amNothing wrong with opening up the housing bores .0005 as long as there within spec. If you try to run every hosing bore on the absolute small end, you will at some point find bearings that the sides will try to close in on.BabyFinster wrote: ↑Sun Mar 29, 2020 11:35 pm I'm in shock on some of the replies to your post. First, other than the plasti-gauge, what are you checking the bearing clearance with? Some have mentioned using the Sunnen dial bore gauge, or a bore gauge of similar fashion. While the "bore gauge" is fairly accurate it not, repeat, not the definitive say on clearance. Here is the dilemma.... the carbide stylus, due to spring pressure, plus the feet will dig into the bearing. If you turn the spring tension down low enough to not drag the stylus, it will not center. Secondly, would you check a curved surface with a standard mic? Due to the dial bore gauge (the Sunnen model) being used repeatedly in a 4"+ bore, the stylus has worn itself almost flat, the line bore gauge would not be as inaccurate. I realize this equates to around .0003 to .0004, however if you had an extra .0004 clearance, this post wouldn't exist.
Increasing housing bore diameter is a dangerous scenario, in today's boosted or nitrous world.... main cap bounce is a very real issue.If you know your math (Pi=3.1415) if you were to open up the housing bore .0005, it should increase bearing clearance approx .0015, taking into account the housing bore is within .0002 @ any position with no shadows on the parting line or cap. If you were on the tight, a few more tenths in the housing bore clearance shouldn't present a problem. Stay away from max diameter whenever possible, hearty bearing crush is your friend. Also, ACL offers bearings in .009, and .011 undersizes to dial in your clearance when the crankshaft has been turned .010. I am unaware of any manufacturer that offers this in anything other than .010, however there may be an offering somewhere on the planet.
I cannot begin to fathom anyone sanding bearings for clearance..... this is wrong on so many levels, I don't know where to start. First, you are changing concentricity, meaning the bearing is no longer centered to the axis of the crank. Sure, there's more clearance, but what effect is having on the rest of the bearing? No one on this forum has the ability to answer the question. Taper, oil pressure bleed off, I could go on and on.
Re-grinding? If I could find a shop that could take .0005 off, you have my business for the rest of my natural life. The shear nature of the process dictates it's an impossibility. You are attempting to take .00025 off with a consumable, the grinding stone. Let's say you could for arguments sake, and managed to get the .00025 off the number 1 main. By the time you got the number 5 main, the rest of it is going to be a mess if we're using .0001. The slightest pressure indifference on the steady rest is going to have you chasing your tail, ultimately working into a bigger problem. I would love to run a profilometer over those journals.... it would look like the Swiss Alps.
Let's talk heat. How much additional clearance would you calculate the clearances open to at operating temperature? Surely we have all honed blocks to where is you could not touch the cylinder. Letting it cool, you are now say .0007 to .001 tight when you were to size previously.... The crankshaft is a much denser alloy, and would expand somewhat, but nothing like cast iron would. How about Aluminum? So is it a half? 3 tenths? I can tell you approximately it is around .0005 to .0007 depending on. How do I know this? We heated blocks to operating temperature and measured clearance. We also ran 190 degree water thru the block while honing to final size.
.002 clearance will be absolutely fine. Ever looked at the back of a bearing on freshen up? The hone marks are impregnated in the steel backing, giving it a couple two three tenths.
Enough ranting, best of luck on your build. baby finster.jpg
Tightening up the hosing bores .0005 will not tighten up the vertical clearance .0015. It will be closer to .0005. Don’t know how many blocks you have align honed but I’m guessing probably very few.
Cheers.
-
- New Member
- Posts: 7
- Joined: Sun Mar 29, 2020 9:35 pm
- Location: Calanazi, CA
Re: Unsure what to do with 0.0020" Main Clearance
Well stated, Sir.gmrocket wrote: ↑Mon Mar 30, 2020 9:10 amYup, that’s why the bearing manufacturers give a max,, it will still give enough crush.houser45 wrote: ↑Mon Mar 30, 2020 8:01 amNothing wrong with opening up the housing bores .0005 as long as there within spec. If you try to run every hosing bore on the absolute small end, you will at some point find bearings that the sides will try to close in on.BabyFinster wrote: ↑Sun Mar 29, 2020 11:35 pm I'm in shock on some of the replies to your post. First, other than the plasti-gauge, what are you checking the bearing clearance with? Some have mentioned using the Sunnen dial bore gauge, or a bore gauge of similar fashion. While the "bore gauge" is fairly accurate it not, repeat, not the definitive say on clearance. Here is the dilemma.... the carbide stylus, due to spring pressure, plus the feet will dig into the bearing. If you turn the spring tension down low enough to not drag the stylus, it will not center. Secondly, would you check a curved surface with a standard mic? Due to the dial bore gauge (the Sunnen model) being used repeatedly in a 4"+ bore, the stylus has worn itself almost flat, the line bore gauge would not be as inaccurate. I realize this equates to around .0003 to .0004, however if you had an extra .0004 clearance, this post wouldn't exist.
Increasing housing bore diameter is a dangerous scenario, in today's boosted or nitrous world.... main cap bounce is a very real issue.If you know your math (Pi=3.1415) if you were to open up the housing bore .0005, it should increase bearing clearance approx .0015, taking into account the housing bore is within .0002 @ any position with no shadows on the parting line or cap. If you were on the tight, a few more tenths in the housing bore clearance shouldn't present a problem. Stay away from max diameter whenever possible, hearty bearing crush is your friend. Also, ACL offers bearings in .009, and .011 undersizes to dial in your clearance when the crankshaft has been turned .010. I am unaware of any manufacturer that offers this in anything other than .010, however there may be an offering somewhere on the planet.
I cannot begin to fathom anyone sanding bearings for clearance..... this is wrong on so many levels, I don't know where to start. First, you are changing concentricity, meaning the bearing is no longer centered to the axis of the crank. Sure, there's more clearance, but what effect is having on the rest of the bearing? No one on this forum has the ability to answer the question. Taper, oil pressure bleed off, I could go on and on.
Re-grinding? If I could find a shop that could take .0005 off, you have my business for the rest of my natural life. The shear nature of the process dictates it's an impossibility. You are attempting to take .00025 off with a consumable, the grinding stone. Let's say you could for arguments sake, and managed to get the .00025 off the number 1 main. By the time you got the number 5 main, the rest of it is going to be a mess if we're using .0001. The slightest pressure indifference on the steady rest is going to have you chasing your tail, ultimately working into a bigger problem. I would love to run a profilometer over those journals.... it would look like the Swiss Alps.
Let's talk heat. How much additional clearance would you calculate the clearances open to at operating temperature? Surely we have all honed blocks to where is you could not touch the cylinder. Letting it cool, you are now say .0007 to .001 tight when you were to size previously.... The crankshaft is a much denser alloy, and would expand somewhat, but nothing like cast iron would. How about Aluminum? So is it a half? 3 tenths? I can tell you approximately it is around .0005 to .0007 depending on. How do I know this? We heated blocks to operating temperature and measured clearance. We also ran 190 degree water thru the block while honing to final size.
.002 clearance will be absolutely fine. Ever looked at the back of a bearing on freshen up? The hone marks are impregnated in the steel backing, giving it a couple two three tenths.
Enough ranting, best of luck on your build. baby finster.jpg
Tightening up the hosing bores .0005 will not tighten up the vertical clearance .0015. It will be closer to .0005. Don’t know how many blocks you have align honed but I’m guessing probably very few.
Yet some on here are more than willing to hand sand the backside, to remove concentricity and crush... before going to a concentric housing bore that’s within recommended specs
Re: Unsure what to do with 0.0020" Main Clearance
Fat cranks sure can make life frustrating for engine builders! When we are hunting for a a few more tenths of main oil clearance AFTER we have line honed block to max housing bore spec, crank has been polished as far as we are comfortable doing, and all bearing size options have been tried, then we go after the back of the bearing shells. Typically there is quite a bit of raised, displaced steel around the letter and numbers stamped on the back of the shells. Many times the shells will also have displaced steel all along the edges lengthwise. A skilled machinist armed with a fine precision file or diamond lapp can detail the back of the shells to gain a few tenths of a thou clearance and IMPROVE accuracy and heat transfer. Now try to get paid for your time!
Carlquist Competition Engines