Spun 5 and 6 after rebuild
09-17-2009, 11:37 AM
#1
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Spun 5 and 6 after rebuild I rebuilt my engine and after 1,000+ miles I had metal in the oil and a knock. After tearing it back down I found #5 and #6 rod bearings spun. The rest of the bearings looked good,other than some metal going through the motor. When I rebuilt it I had the crank turned and replaced most everything. Eagle rods,Wiseco pistons,LS1 oil pump,roller timing set,cam,lifter,pushrods,etc...everything new. My question is what would cause 5 and 6 to go? Will a 6.0l crank work in my 5.7 block?
09-17-2009, 12:29 PM
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I checked the clearance's when I assembled it and everything was good. Oil pressure was good too,gauge showed almost 60 at idle but as the noise came the pressure dropped,before I pulled it out it still had 30+ hot at an idle.
Would 5,6 be affected by oil press first or 7,8 since they are furthest from the oil pump?
Would 5,6 be affected by oil press first or 7,8 since they are furthest from the oil pump?
09-17-2009, 01:32 PM
#6
Was the clearances too tight? I've read some other post where the clearances were set on the tight side (.0008-.0012) which is within GM specs for a production engine. However, many has complained that those clearances proved to be too tight when building for higher HP and RPM. If you had 60psi hot oil pressure and 30 when things let go, I'll say they were on the tight side.
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09-18-2009, 06:51 AM
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Everything else looked GREAT....of course there was a little metal in the other bearings but none of the other rods or the mains had any signs of wear.
09-18-2009, 12:02 PM
#11
Some people have problems with tight clearances after mods are done and some don't. .0015 is well within GM specs, but I would not want extra tight clearances on the rods or mains after rebuilding it for higher HP. From what I've read you can set the mains up at .0015 because the aluminum constructed block will increase the clearance by about .001 when brought up to operating temps. However, the rods will not expand as much, therefore I would try to set them at .002 minimum. Let me point out that I'm in NO WAY a professional engine builder but a home hobbyist that has built a few SBC's and BBC's. I'm new to the LS family so maybe I can learn something here also. What type of RPM was you turning?
Last edited by Monte4ever; 09-18-2009 at 12:36 PM.
09-20-2009, 09:13 AM
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Some people have problems with tight clearances after mods are done and some don't. .0015 is well within GM specs, but I would not want extra tight clearances on the rods or mains after rebuilding it for higher HP. From what I've read you can set the mains up at .0015 because the aluminum constructed block will increase the clearance by about .001 when brought up to operating temps. However, the rods will not expand as much, therefore I would try to set them at .002 minimum. Let me point out that I'm in NO WAY a professional engine builder but a home hobbyist that has built a few SBC's and BBC's. I'm new to the LS family so maybe I can learn something here also. What type of RPM was you turning?
09-20-2009, 12:24 PM
#15
I would say that the clearances were to tight. When clearances get tighter everything has to be perfect as far as roundness etc. That is why you can get by with tighter clearances sometimes. The looser clearances also let more oil through which helps keep the bearing cool. Bearing metal is very soft.
09-20-2009, 05:58 PM
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60 psi oil pressure seems allot on an ls1 oil pump, i have a meling 296 and i have 55 psi idle. and that's a high volume/high pressure pump.
anyway, i think the high oil pressure was giving you a sign that the bearing clearances are too tight.
anyway, i think the high oil pressure was giving you a sign that the bearing clearances are too tight.
09-20-2009, 06:48 PM
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Your clearances were a little on the tight side. I'm not saying that there is no way they could survive that way but I wouldn't set the rods that tight. A good rule of thumb is to have .001" of clearance per inch diameter of the journal. The LS1 has a 2.100" rod journal so .0021" clearance would work for most applications.
09-21-2009, 11:01 AM
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I would say that the clearances were to tight. When clearances get tighter everything has to be perfect as far as roundness etc. That is why you can get by with tighter clearances sometimes. The looser clearances also let more oil through which helps keep the bearing cool. Bearing metal is very soft.
