Main Clearances...
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TECH Junkie
iTrader: (11)
Joined: Jul 2005
Posts: 3,782
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From: Port Neches, TX
Main Clearances... Should I be worried? Had this block line-bored and here are the results:
#1 = 0.0013"
#2 = 0.0015"
#3 = 0.0016" (0.007" thrust)
#4 = 0.0023"
#5 = 0.0022"
All with standard bearings and a (new) stock LS7 crank, journals measured with a micrometer and bearing bores with dial bore gauge. At least I should have outstanding oil pressure...
#1 = 0.0013"
#2 = 0.0015"
#3 = 0.0016" (0.007" thrust)
#4 = 0.0023"
#5 = 0.0022"
All with standard bearings and a (new) stock LS7 crank, journals measured with a micrometer and bearing bores with dial bore gauge. At least I should have outstanding oil pressure...
I'm assuming this is an aluminum block and that the crank has been balanced/polished already.
The two back mains seem good, I'd remove the front three sets of bearing shells and hand scotch brite scrub them in a solvent tank. The last little procedure you can do is put the shell on a workbench, backside down and roll a wrist pin back and forth across the babbit layer, gently rocking the shell back and forth like you're rolling pizza dough. These two goofy steps will get the front clearances in that .0022"-.0023" range.
The two back mains seem good, I'd remove the front three sets of bearing shells and hand scotch brite scrub them in a solvent tank. The last little procedure you can do is put the shell on a workbench, backside down and roll a wrist pin back and forth across the babbit layer, gently rocking the shell back and forth like you're rolling pizza dough. These two goofy steps will get the front clearances in that .0022"-.0023" range.
Banned
Joined: Aug 2006
Posts: 326
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From: North Bay, CA
I would want to know what the main housing bore actually measures at...a full .001" spread and with where it's happening it looks like a lazy machinist didn't flip his mandrel if it was a line hone, or a worn line bore machine if it was only bored.
Launching!
Joined: Dec 2014
Posts: 215
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Agreed, do it once do it it right.
Thread Starter
TECH Junkie
iTrader: (11)
Joined: Jul 2005
Posts: 3,782
Likes: 7
From: Port Neches, TX
This is what I have:
---------journal ----- bearing ---- clearance
#1 ----- 2.5598 ----- 2.5611 ----- 0.0013
#2 ----- 2.5595 ----- 2.5610 ----- 0.0015
#3 ----- 2.5595 ----- 2.5611 ----- 0.0016 ----- (0.007 thrust)
#4 ----- 2.5595 ----- 2.5618 ----- 0.0023
#5 ----- 2.5593 ----- 2.5615 ----- 0.0022
The journals are all on the high side of the 2.5595 spec with a variance of 0.0005", the bearings have a variance of 0.0008". These are prolly within my margin of error. All I have read on alum blocks say 0.001 to 0.002 since the thermal expansion will open them up. One of my buds suggested the boring bar was wobbling, IDK, that's out of my control. Personally, I don't see a problem running it as-is. I don't think it's gonna come apart, cost HP, use excess oil, etc. If ya'll can say definitively why I should NOT run it, please post that reply.
Thanks!
EDIT: 171-MS-2199P - Clevite P-Series Main Bearing Set for STOCK CRANK APPLICATIONS
---------journal ----- bearing ---- clearance
#1 ----- 2.5598 ----- 2.5611 ----- 0.0013
#2 ----- 2.5595 ----- 2.5610 ----- 0.0015
#3 ----- 2.5595 ----- 2.5611 ----- 0.0016 ----- (0.007 thrust)
#4 ----- 2.5595 ----- 2.5618 ----- 0.0023
#5 ----- 2.5593 ----- 2.5615 ----- 0.0022
The journals are all on the high side of the 2.5595 spec with a variance of 0.0005", the bearings have a variance of 0.0008". These are prolly within my margin of error. All I have read on alum blocks say 0.001 to 0.002 since the thermal expansion will open them up. One of my buds suggested the boring bar was wobbling, IDK, that's out of my control. Personally, I don't see a problem running it as-is. I don't think it's gonna come apart, cost HP, use excess oil, etc. If ya'll can say definitively why I should NOT run it, please post that reply.
Thanks!
EDIT: 171-MS-2199P - Clevite P-Series Main Bearing Set for STOCK CRANK APPLICATIONS
Last edited by S10xGN; Aug 11, 2015 at 07:51 PM. Reason: forgot bearing specs
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There's problably some variance in the main bearings. I would try switching out the #1 and 2 bearings with the #4 and 5 bearings. That will sometimes make the difference.
Only .0013" on the mains is too tight for my liking but I have no empirical data to support my opinion. Clevite suggests at least .001" for every 1" of journal diameter, but I feel that's too loose for an aluminum block. That tight clearance might actually be perfectly fine for what you're doing and run forever, but I would want it a little looser. As the saying goes, "Too loose and only you know. Too tight and everyone will know."
Only .0013" on the mains is too tight for my liking but I have no empirical data to support my opinion. Clevite suggests at least .001" for every 1" of journal diameter, but I feel that's too loose for an aluminum block. That tight clearance might actually be perfectly fine for what you're doing and run forever, but I would want it a little looser. As the saying goes, "Too loose and only you know. Too tight and everyone will know."
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Brett Foote Launching!
Joined: Dec 2014
Posts: 215
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This is what I have:
---------journal ----- bearing ---- clearance
#1 ----- 2.5598 ----- 2.5611 ----- 0.0013
#2 ----- 2.5595 ----- 2.5610 ----- 0.0015
#3 ----- 2.5595 ----- 2.5611 ----- 0.0016 ----- (0.007 thrust)
#4 ----- 2.5595 ----- 2.5618 ----- 0.0023
#5 ----- 2.5593 ----- 2.5615 ----- 0.0022
The journals are all on the high side of the 2.5595 spec with a variance of 0.0005", the bearings have a variance of 0.0008". These are prolly within my margin of error. All I have read on alum blocks say 0.001 to 0.002 since the thermal expansion will open them up. One of my buds suggested the boring bar was wobbling, IDK, that's out of my control. Personally, I don't see a problem running it as-is. I don't think it's gonna come apart, cost HP, use excess oil, etc. If ya'll can say definitively why I should NOT run it, please post that reply.
Thanks!
EDIT: 171-MS-2199P - Clevite P-Series Main Bearing Set for STOCK CRANK APPLICATIONS
---------journal ----- bearing ---- clearance
#1 ----- 2.5598 ----- 2.5611 ----- 0.0013
#2 ----- 2.5595 ----- 2.5610 ----- 0.0015
#3 ----- 2.5595 ----- 2.5611 ----- 0.0016 ----- (0.007 thrust)
#4 ----- 2.5595 ----- 2.5618 ----- 0.0023
#5 ----- 2.5593 ----- 2.5615 ----- 0.0022
The journals are all on the high side of the 2.5595 spec with a variance of 0.0005", the bearings have a variance of 0.0008". These are prolly within my margin of error. All I have read on alum blocks say 0.001 to 0.002 since the thermal expansion will open them up. One of my buds suggested the boring bar was wobbling, IDK, that's out of my control. Personally, I don't see a problem running it as-is. I don't think it's gonna come apart, cost HP, use excess oil, etc. If ya'll can say definitively why I should NOT run it, please post that reply.
Thanks!
EDIT: 171-MS-2199P - Clevite P-Series Main Bearing Set for STOCK CRANK APPLICATIONS
In principal you should have them all 'nuts on'.002" However, I have seen main's as close as .0005" and live! So you definitely won't have an issue running what you have ended up with.
Cheers,
Mark.
Thread Starter
TECH Junkie
iTrader: (11)
Joined: Jul 2005
Posts: 3,782
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From: Port Neches, TX
Thanks for the input, but I need to put this up until fall. Unbagged it today and there were rust stains (from sweat drippings) in the bores. Hard to work comfortably when it's 104° with an index of 115°...
Thread Starter
TECH Junkie
iTrader: (11)
Joined: Jul 2005
Posts: 3,782
Likes: 7
From: Port Neches, TX
Had a nice day here today, weather was mid-80's and 35% humidity, so back to work. I pulled the crank, cleaned and inspected everything, and reset my dial bore gauge for each individual main. Also swapped the shells from #1 to #5 and #2 to #4 and got these numbers:
#1 = 0.0017"
#2 = 0.0020"
#3 = 0.0019" (0.007" thrust)
#4 = 0.0021"
#5 = 0.0019"
The first time, I did over-torque the studs to 70# (trying to work from memory) but reset them all when I found out a couple hrs later. I miked each shell in 6 places to make sure nothing was crushed and all spots were within 0.0002". Also checked the studs against ARP's stated lengths and while some were + 0.003", a couple were actually shorter. I feel better now...
#1 = 0.0017"
#2 = 0.0020"
#3 = 0.0019" (0.007" thrust)
#4 = 0.0021"
#5 = 0.0019"
The first time, I did over-torque the studs to 70# (trying to work from memory) but reset them all when I found out a couple hrs later. I miked each shell in 6 places to make sure nothing was crushed and all spots were within 0.0002". Also checked the studs against ARP's stated lengths and while some were + 0.003", a couple were actually shorter. I feel better now...