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Old September 23rd, 2009, 03:38 AM   #1
CountryBoy350
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Cam Bearings?

Ok so I drove my 94 F150 without oil pressure and I know I spun all my rod and main bearings. I just had the crank reground, replaced the rod, and main bearings, and started putting the whole motor back together. But I was just thinking that since those bearings went, shouldn't my camshaft bearings be screwed too???

When I started this rebuild I really didn't know what I was doing, so I hired this kid that told me he knew how to rebuild a motor to kind of help me out and show me what to do. Well it turns out the dumbass has no idea what the hell he's doing, and now I understand why his truck went up in flames a half hour after he rebuilt his motor. So do I have to take the whole motor back apart now and replace those cam bearings or what?

Last edited by CountryBoy350; September 23rd, 2009 at 04:02 AM.
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Old September 23rd, 2009, 04:42 AM   #2
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I have done several budget builds and have excluded cam bearings in them. a few specific engine you can't skip them like 2.8,3.1 & 3.4 liter chevys. the majority of engine have very little side load & wear on cam bearing even with low oil presure. since the cam is normally fed first in the line of things they ussally last when the crank fails. one of the things you talked about was "Spinning" the bearings, did you replace the rods that they spun on? if not then you'd better stop now. secondly if the crank spun any in the block and caused damage the block would need to be re aline bored.
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Old September 23rd, 2009, 04:56 AM   #3
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I have done several budget builds and have excluded cam bearings in them. a few specific engine you can't skip them like 2.8,3.1 & 3.4 liter chevys. the majority of engine have very little side load & wear on cam bearing even with low oil presure. since the cam is normally fed first in the line of things they ussally last when the crank fails. one of the things you talked about was "Spinning" the bearings, did you replace the rods that they spun on? if not then you'd better stop now. secondly if the crank spun any in the block and caused damage the block would need to be re aline bored.
Well I had a few guys take a look at the rods, block, and crank, and they all say that they still seem to be in good shape. I only ran the motor for 15 minutes with no oil pressure, but that was enough to screw the bearings and give it a very light knock. The oil pump seized up and that's what caused the damage. But honestly I probably could have just replaced the oil pump and the motor probably would've lasted a while since it wasn't knocking that bad at all. It did lose a pretty good amount of power though.

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Old September 23rd, 2009, 05:13 AM   #4
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the worst I seen made it 40,000 and they ran it till the pan cooked dry. totally wiped it out.

now as far as damage, if the motor knocked and the bearings were just gouged a little, they may not have spun, but when the knock under load comes and goes that is because the two halves of the bearing are moving inside the rod cap, they wedge themselves here & there in various positions and stop the noise from time to time. thats what cause the majority of damage.
as far as damage goes I guess it has yet to be seen by me that a spun rod can take another bearing without failing. when a rod spins a bearing it ussally makes an egg shape out of the end that holds the bearing and soon fails because it can no longer hold the bearing secure. just my $.02
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Old September 23rd, 2009, 05:21 AM   #5
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the worst I seen made it 40,000 and they ran it till the pan cooked dry. totally wiped it out.

now as far as damage, if the motor knocked and the bearings were just gouged a little, they may not have spun, but when the knock under load comes and goes that is because the two halves of the bearing are moving inside the rod cap, they wedge themselves here & there in various positions and stop the noise from time to time. thats what cause the majority of damage.
as far as damage goes I guess it has yet to be seen by me that a spun rod can take another bearing without failing. when a rod spins a bearing it ussally makes an egg shape out of the end that holds the bearing and soon fails because it can no longer hold the bearing secure. just my $.02
Ya know, now that I think about it I don't think they really did spin. The old bearings were still seated in the connecting rods where they should be when I took it apart, but they were completely worn. The connecting rods also have very little wear on them at all.

Here's a pic of one of the bearings

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Old September 23rd, 2009, 05:31 AM   #6
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and this is the best pic i have of the rod with new bearings
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Old September 23rd, 2009, 09:47 PM   #7
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spun bearings means the bearing changed location, basically...often one half spins over top of the other, or the both spin inside the rod or main bearing cap/block (like Yetti described)...this will almost always destroy the hole the bearing is suposed to be in, and normally shears off the locking tab....I've never seen an engine spin every bearing, and its highly unlikey yours did that...sounds like you actually just wore the bearings, so by replacing the main and rod bearings, even leaving the cam bearings (though they should have been looked at, in the least) you will probably be fine to run it
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