.0004-.0005 Clearance on mains, new bearings
01-05-2004, 07:38 PM
#1
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.0004-.0005 Clearance on mains, new bearings I dont remember the LS1 clearances off hand, but a friend of mine is putting new bearings in his 346" stock rods/crank ls1. The old bearings only had 20k miles on them & same mileage on rods/crank. He just put them in because he had it apart to put forged pistons in.
On the mains he got .0004 thousandths on 3 caps and about .00045-.0005 on the other 2
Most guys aim for .0002-.0003.
Also he reused the factory mains (which you shouldnt but he is) and the torque spec is 15 lbs + 80 degrees. Shouldnt have he to torque it alittle now that the bolts are already pre stretched? If hes not going to put new bolts in, i told him he might want to try torqueing it to 15 lbs + 100 degrees and check his main clearance again.
Will 4-5 thousandths work or no?
Any ideas? (this isnt what i would do building a motor, but i dont build the motors in our shop, our engine builder does and hes not here).
On the mains he got .0004 thousandths on 3 caps and about .00045-.0005 on the other 2
Most guys aim for .0002-.0003.
Also he reused the factory mains (which you shouldnt but he is) and the torque spec is 15 lbs + 80 degrees. Shouldnt have he to torque it alittle now that the bolts are already pre stretched? If hes not going to put new bolts in, i told him he might want to try torqueing it to 15 lbs + 100 degrees and check his main clearance again.
Will 4-5 thousandths work or no?
Any ideas? (this isnt what i would do building a motor, but i dont build the motors in our shop, our engine builder does and hes not here).
01-05-2004, 07:59 PM
#2
Originally Posted by C4VetteLS1
I dont remember the LS1 clearances off hand, but a friend of mine is putting new bearings in his 346" stock rods/crank ls1. The old bearings only had 20k miles on them & same mileage on rods/crank. He just put them in because he had it apart to put forged pistons in.
On the mains he got .0004 thousandths on 3 caps and about .00045-.0005 on the other 2
Most guys aim for .0002-.0003.
Also he reused the factory mains (which you shouldnt but he is) and the torque spec is 15 lbs + 80 degrees. Shouldnt have he to torque it alittle now that the bolts are already pre stretched? If hes not going to put new bolts in, i told him he might want to try torqueing it to 15 lbs + 100 degrees and check his main clearance again.
Will 4-5 thousandths work or no?
Any ideas? (this isnt what i would do building a motor, but i dont build the motors in our shop, our engine builder does and hes not here).
On the mains he got .0004 thousandths on 3 caps and about .00045-.0005 on the other 2
Most guys aim for .0002-.0003.
Also he reused the factory mains (which you shouldnt but he is) and the torque spec is 15 lbs + 80 degrees. Shouldnt have he to torque it alittle now that the bolts are already pre stretched? If hes not going to put new bolts in, i told him he might want to try torqueing it to 15 lbs + 100 degrees and check his main clearance again.
Will 4-5 thousandths work or no?
Any ideas? (this isnt what i would do building a motor, but i dont build the motors in our shop, our engine builder does and hes not here).
Factory spec. on main bearing clearance is .0007" to .0021". I generally aim for the center of this range as I am certain is the case with most engine builders. I think you are confusing tenths of a thousandth with thousandths. Your figure of .0004" - .0005" is what is termed four to five tenths clearance in the trade. This is insufficient. If on the other hand you are off one decimal place and your measured clearance is .004" to .005" you have way too much clearance unless this is a top fuel motor!
Use new fasteners. I prefer studs for most applications but ARP bolts will work fine. The factory bolts, either head or main, should not be reused. The factory uses torque to yield bolts. These bolts are put under much greater tensile load than normal high performance hardware when tightened per factory procedures. You run a great risk of bolt failure if you reuse the original fasteners.
Steve Demirjian
Race Engine Development
Last edited by Steve - Race Eng; 01-05-2004 at 08:05 PM. Reason: Forgot your bolt question
01-05-2004, 08:10 PM
#3
I guess my first reponse would be, WTF would he go forged pistons(I know the answer to that)and NOT use good studs/bolts, or AT LEAST new TTY bolts in the mains 
I don't follow the logic. I geuss that's not for me to understand though....
Factory mains are fine unless he's gone insane on his PA, but if that's the case....see above.
I know some folks re-use the stock main/rod bolts and have had no issues. You will not get an accurrate TTY # on a pre-stretched bolt. I would "think" that by torqueing over spec, you "could" run the risk of snapping the bolt? Dunno, as I've never re-used a TTY bolt. I guesss if I were going that route, I'd put ~ another 30-45* on the Tq. angle to ensure propper clamping pressures? I guess he could tq. angle in increments until he got his oil clearences to spec(0.0007-0.0021), but don't know how much more angle that is on a stretched bolt, and where the bolt's failure point is.
Can't answer w/any certainy on the main cap #'s. .00045-.0005 seems a lil' loose on a bolt that you don't really know if that's what you've really got.
Talk him into doing it right for the sake of longevity.....no reason to skimp on bolts, just to come back later and re-build the carnage. JMFUO...
I don't follow the logic. I geuss that's not for me to understand though....Factory mains are fine unless he's gone insane on his PA, but if that's the case....see above.
I know some folks re-use the stock main/rod bolts and have had no issues. You will not get an accurrate TTY # on a pre-stretched bolt. I would "think" that by torqueing over spec, you "could" run the risk of snapping the bolt? Dunno, as I've never re-used a TTY bolt. I guesss if I were going that route, I'd put ~ another 30-45* on the Tq. angle to ensure propper clamping pressures? I guess he could tq. angle in increments until he got his oil clearences to spec(0.0007-0.0021), but don't know how much more angle that is on a stretched bolt, and where the bolt's failure point is.
Can't answer w/any certainy on the main cap #'s. .00045-.0005 seems a lil' loose on a bolt that you don't really know if that's what you've really got.
Talk him into doing it right for the sake of longevity.....no reason to skimp on bolts, just to come back later and re-build the carnage. JMFUO...
01-05-2004, 09:25 PM
#4
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I do agree with Steve. You probably meant .004-.005".
How is he measuring the bearing clearance? The best way is to measure the main journal diameters with a good, quality micrometer that resolves to .0001". Once this value is obtained, zero your dial bore gauge to the journal diameter measured. With the main caps torque and the bearing installed, measure the inside diameter of the bearing installed in main cap. The measurement on your dial bore gauge will be your bearing clearance (+ side of the gauge). Just remember you will have to re-zero your dial bore gauge for each change in journal diameter.
Another thing to look into (if the clearances you measured were accurate) would be the main housing bore diameter. If it is out of spec (on the loose side), your bearing clearance will increase. The maximum housing bore diameter is 2.7515" if I remember correctly (I can check in the morning).
Also check to make sure the bearings are indeed STD bearings. I have seen some cases where the wrong bearings were packed from the manufacturer.
From the LS1s I have built, a STD/STD set of Federal Mogul bearings (152M) will very rarely give you the desired clearance (I shoot for .0017-.0018" on the mains), especially if the housing bore is on the looser side of the factory specifications. I usually end up with a +1/STD bearing set to achieve the above clearance.
Jason
How is he measuring the bearing clearance? The best way is to measure the main journal diameters with a good, quality micrometer that resolves to .0001". Once this value is obtained, zero your dial bore gauge to the journal diameter measured. With the main caps torque and the bearing installed, measure the inside diameter of the bearing installed in main cap. The measurement on your dial bore gauge will be your bearing clearance (+ side of the gauge). Just remember you will have to re-zero your dial bore gauge for each change in journal diameter.
Another thing to look into (if the clearances you measured were accurate) would be the main housing bore diameter. If it is out of spec (on the loose side), your bearing clearance will increase. The maximum housing bore diameter is 2.7515" if I remember correctly (I can check in the morning).
Also check to make sure the bearings are indeed STD bearings. I have seen some cases where the wrong bearings were packed from the manufacturer.
From the LS1s I have built, a STD/STD set of Federal Mogul bearings (152M) will very rarely give you the desired clearance (I shoot for .0017-.0018" on the mains), especially if the housing bore is on the looser side of the factory specifications. I usually end up with a +1/STD bearing set to achieve the above clearance.
Jason
01-05-2004, 09:59 PM
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Ok! I talked him into using a set of ARP main bolts i have at the shop.
It took almost ZERO effort to torque the factory used bolts to 80 degrees (id guess 40-50 lbs of torque) and the ARP studs are 65 lbs i think.
Would you think the clearances would be tighter at 65lbs then 40-50lbs?
It took almost ZERO effort to torque the factory used bolts to 80 degrees (id guess 40-50 lbs of torque) and the ARP studs are 65 lbs i think.
Would you think the clearances would be tighter at 65lbs then 40-50lbs?
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01-05-2004, 10:04 PM
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hahaha..no it was balanced...
and now we got arp main studs going into it...
I think im going to take over putting this motor together before it goes boom
and now we got arp main studs going into it...
I think im going to take over putting this motor together before it goes boom
01-06-2004, 07:14 AM
#9
I usually shoot for .002 to .003, but don't get too concerned unless they are tighter than .0015 or looser than .003. I don't think the TTY mains are as likely to stretch as the head bolts due to being a different material and the fact that thaey are not torqued nearly as much as head bolts. I always recommend ARP main studs when I rebuild someone else's motor though 
01-06-2004, 07:33 AM
#10
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Never ever ever ever re-use TTY bolts. If you do, you are asking for trouble. Understand what TTY is. Torque to Yield.... That should give you an idea of what the bolt is doing. You are putting the fastner in a "stretched" condition. It has a certain elasticity at this point. This is particularly good when you are using dis-similar metals like an aluminum head and an iron block, since they have different rates of expansion. It allows for it to stetch, and still have good clamping force.
Once a fastner is streched, thats it. It is pretty much a one time use deal. To re-use them is only asking for issues. On the clearances, I think most folks have summed it up. If you don't have a good mic/inside bore gauge to check the stuff, at least get some plastigauge and check it and make sure you have the proper clearances.
Once a fastner is streched, thats it. It is pretty much a one time use deal. To re-use them is only asking for issues. On the clearances, I think most folks have summed it up. If you don't have a good mic/inside bore gauge to check the stuff, at least get some plastigauge and check it and make sure you have the proper clearances.
01-06-2004, 08:33 AM
#11
J-Rod...all your points are valid. But there is such a thing as needless worrying, and I believe this is not a good time for it. If you think about the design of the LS1 mains with the sdie bolts and all, there is very little reason for a main bolt to loosen. Not saying it can't happen, but to this date, have you seen it?
01-06-2004, 09:58 AM
#13
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Its not a matter of needless worry, its about the correct procedure for assembling a motor. As a general rule of thumb, once a TTY fastener has been stretched, it is no longer re-usable period. Its not to say that you can't, you simply are not supposed to. Its like setting up springs. Do you have to check them, no actually, you can just pop them on the heads and hope for the best. You might get lucky and they ar right where you need them to be, on the other hand they could be way off. Again, the proper procedure is to check your set-up height. As a side note, TTY bolt heads will snap if they become over-stretched.
Here is what Joe Mondello says about fasteners:
Here is what Joe Mondello says about fasteners:
There are three types of procedures used for torquing: torque to yield/angle to turn; torque to maximum stretch yield; and torque to a specific torque number and hope it's correct. If cycling is not done properly, especially before machining, your dimensions will change drastically in the cylinder bore, cam tunnel and main bearing housing bore. I have seen these dimensions change anywhere from .0004" to .0015" and the size gets smaller not bigger.
On all performance fasteners you must cycle the bolts or studs four or five times before any machine work like boring or honing can be done. If you’re using torque plates, use the same fasteners and gaskets, especially if you’re using a hard or soft wire o-ring gasket. If this isn’t done, as much as 0.0004” to 0.0015” less diameter will be noticed. If you don’t torque cycle the main caps four or five times, between .0002" and .0007" less diameter will be noticed.
We have used many rod bolt torque specs of 60 to 65 lbs. that are supposed to stretch the bolt .0058” to .0063” and it only stretched the bolt 0.0034”. Usually it will take between 80 and 94 lbs. to obtain the proper stretch. Buy yourself a rod bolt stretch gauge. You will be surprised how far off you have been. And always follow the torque sequence supplied by the manufacturer; otherwise you won’t achieve your maximum clamping force. Once a non-“J” type aircraft quality bolt is torqued to a specific figure, then stretched another 30° to 80° to stretch it to maximum yield and clamping force, I fell they should be thrown away. New ones should be used each time the heads are changed. If you are angle torquing there are several angle gauges I recommend. Fel-Pro, K-line and Snap-On are real good. I’m sure there are many more good ones out there. I use these at my school.
On all performance fasteners you must cycle the bolts or studs four or five times before any machine work like boring or honing can be done. If you’re using torque plates, use the same fasteners and gaskets, especially if you’re using a hard or soft wire o-ring gasket. If this isn’t done, as much as 0.0004” to 0.0015” less diameter will be noticed. If you don’t torque cycle the main caps four or five times, between .0002" and .0007" less diameter will be noticed.
We have used many rod bolt torque specs of 60 to 65 lbs. that are supposed to stretch the bolt .0058” to .0063” and it only stretched the bolt 0.0034”. Usually it will take between 80 and 94 lbs. to obtain the proper stretch. Buy yourself a rod bolt stretch gauge. You will be surprised how far off you have been. And always follow the torque sequence supplied by the manufacturer; otherwise you won’t achieve your maximum clamping force. Once a non-“J” type aircraft quality bolt is torqued to a specific figure, then stretched another 30° to 80° to stretch it to maximum yield and clamping force, I fell they should be thrown away. New ones should be used each time the heads are changed. If you are angle torquing there are several angle gauges I recommend. Fel-Pro, K-line and Snap-On are real good. I’m sure there are many more good ones out there. I use these at my school.
01-06-2004, 11:53 AM
#15
6600 rpm clutch dump of death Administrator
I see it regularly at the machine shop. Mostly on cylinder heads when folks re-use TTYs and the head lifts and they can't seem to understand why they keep blowing head gaskets, and don't want to spring for new bolts...
Want to see someting realy interesting. Watch how much a stock PM rod deforms. When you mic it you'd swear there is no way it will true up. Once you torque it up, boom, its round all of the sudden... Before that though it is all egg shaped....
Want to see someting realy interesting. Watch how much a stock PM rod deforms. When you mic it you'd swear there is no way it will true up. Once you torque it up, boom, its round all of the sudden... Before that though it is all egg shaped....
01-06-2004, 12:08 PM
#16
Well, my thoughts are on a daily driver that is too much. As steve said if its not a top fuel drag car I wouldn't use it. Top fuel drag cars run larger clearances and higher volume/high pressure oil pumps, and not to mention like 20-50 or thicker oil. If you run any street motor with those clearances and a 10w30 or so oil you are asking to turn bearings. Think about this. if clearances are .002-.004 optimally, and you have more than .012 clearances you should move to a .010 oversized bearing. 
01-06-2004, 01:43 PM
#17
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Well guy's.....if the cost of a set of studs or new bolts is to much. What will your world be like if it does cause a engine failure? It's going to cost a lot more to fix the engine than an extra $100. You should not reuse TTY bolts. Spend the money and do it right. This way you won't have to worry about driving over all of your internal engine parts.
Chris
Chris
