bearing clearances too tight?
08-24-2007, 06:51 PM
#1
bearing clearances too tight? I just measured and my main and rod bearing clearances.
Results where
mains
#1 .0015
#2 .0015
#3 .0020
#4 .0017
#5 .0017
Rods
#1 .0015
#2 .0018
#3 .0015
#4 .0015
#5 .0018
#6 .0015
#7 .0018
#8 .0017
Question is how much do you think the main clearances will open up with heat at operating temp? Also i think the rod bearings need another .0005 on the crank to be polished.
Who else thinks the clearances are too tight?
Results where
mains
#1 .0015
#2 .0015
#3 .0020
#4 .0017
#5 .0017
Rods
#1 .0015
#2 .0018
#3 .0015
#4 .0015
#5 .0018
#6 .0015
#7 .0018
#8 .0017
Question is how much do you think the main clearances will open up with heat at operating temp? Also i think the rod bearings need another .0005 on the crank to be polished.
Who else thinks the clearances are too tight?
08-25-2007, 07:37 AM
#4
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as stated by the factory service manual for a 1998 ls1 the connecting rod bearing clearance should be 0.015-0.076mm, so the rods look good The mains if geater than 0.00212" need to be undersized, according to the manual
08-25-2007, 07:51 AM
#5
Originally Posted by rpmauto
as stated by the factory service manual for a 1998 ls1 the connecting rod bearing clearance should be 0.015-0.076mm, so the rods look good The mains if geater than 0.00212" need to be undersized, according to the manual
Is tighter (like factory) specs better or looser? I know i've spun bearings in the past cuz of too tight of clearances but that was with old skool SBC.
08-25-2007, 07:59 AM
#6
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it depends what you are looking to do with the engine. If you want to get long life out of it build it to spec. When i build a race engine i build it looser. looser wont last as long though. High rpms dont cause a bearing to spin unless it is way way to tight. too much clearance and wear will cause a bearing to spin. My .02
08-25-2007, 09:46 AM
#7
I'm building a 6.2L(376)
stock rods
stock crank
stock pistons
MS3
ported 243 ls6 heads
11.8-1 compression
carbed Vic Jr. (might be swapping to performer RPM)
mighty demon 750
1 7/8 headers w/ dual 3in exhaust
looking to drive the truck some but not everyday.
limit rpm around 6700 or so.
Nothing fancy just something that is reliable.
stock rods
stock crank
stock pistons
MS3
ported 243 ls6 heads
11.8-1 compression
carbed Vic Jr. (might be swapping to performer RPM)
mighty demon 750
1 7/8 headers w/ dual 3in exhaust
looking to drive the truck some but not everyday.
limit rpm around 6700 or so.
Nothing fancy just something that is reliable.
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08-26-2007, 03:43 PM
#9
Looks good to me! Here were mine for my 427...
Main #1: .0016
Main #2: .0017
Main #3: .0018
Main #4: .0018
Main #5: .0018
Rods: .0018
Aluminum block motors built reliably for the street like tighter clearances. Drag iron blocks like looser clearances. You will be fine and you will have some good oil pressure also.
Main #1: .0016
Main #2: .0017
Main #3: .0018
Main #4: .0018
Main #5: .0018
Rods: .0018
Aluminum block motors built reliably for the street like tighter clearances. Drag iron blocks like looser clearances. You will be fine and you will have some good oil pressure also.
08-26-2007, 04:13 PM
#10
Originally Posted by Ferocity02
Looks good to me! Here were mine for my 427...
Main #1: .0016
Main #2: .0017
Main #3: .0018
Main #4: .0018
Main #5: .0018
Rods: .0018
Aluminum block motors built reliably for the street like tighter clearances. Drag iron blocks like looser clearances. You will be fine and you will have some good oil pressure also.
Main #1: .0016
Main #2: .0017
Main #3: .0018
Main #4: .0018
Main #5: .0018
Rods: .0018
Aluminum block motors built reliably for the street like tighter clearances. Drag iron blocks like looser clearances. You will be fine and you will have some good oil pressure also.
How high do you spin the motor and how many miles do you have on it with those specs?
Sorry so many ?s just wanted a few opinions before i finish bolting this all together.
TIA
Sroka
08-26-2007, 06:46 PM
#12
Looks like i'm getting answers anywhere from .0018 to .0025?
Does anyone really think it matters if they are exact? Isnt like someone could measure bearing clearances when the motor is up to temp and running. Kinda souds like its the luck of the draw.
Does anyone really think it matters if they are exact? Isnt like someone could measure bearing clearances when the motor is up to temp and running. Kinda souds like its the luck of the draw.
08-26-2007, 06:57 PM
#13
Originally Posted by sroka
So yours is doing fine at those clearance? How high oil pressure are you seeing? Oil pump? oil weight?
How high do you spin the motor and how many miles do you have on it with those specs?
Sorry so many ?s just wanted a few opinions before i finish bolting this all together.
TIA
Sroka
How high do you spin the motor and how many miles do you have on it with those specs?
Sorry so many ?s just wanted a few opinions before i finish bolting this all together.
TIA
Sroka
08-27-2007, 05:25 PM
#15
Originally Posted by Ferocity02
Well i dont have the car anymore, but I put almost 2k miles on it and then tore it down and the bearings and journals were perfect. I ran a ported LS6 pump with 10w-40 and oil pressure was 50 at idle and 70-80 wot warm. I spun it up to 7000rpm.
08-27-2007, 05:39 PM
#16
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The all look a thou tight to me. I've always run between 2 and 3 on my motors. Are Ls1s different than the old SBC? Factory specs for the SBC are similar to the clearances posted, but everyone runs more.
08-27-2007, 07:35 PM
#17
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You have to run more clearance, factory specs are just that.. Factory 300hp specs... Not 400 or 500, etc etc like we're all doing here. Get them over .002"...
08-27-2007, 08:01 PM
#18
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.002" R / .0025" M
Make sure to get your line bore checked even if you have not upgraded to stud, I have seen those blocks settle in quite a bit, or the factory does a poor job - either way the line bore is not were it should be.
Make sure to get your line bore checked even if you have not upgraded to stud, I have seen those blocks settle in quite a bit, or the factory does a poor job - either way the line bore is not were it should be.
08-27-2007, 08:50 PM
#20
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Smaller journals require less clearance... General rule, .001 per 1" of journal... 2.100 rods, should be roughly .0021, and the mains at 2.559 should be roughly .0025"...
