Changing an oil pump and rod bearings
#16
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Are you changing the bearings with the engine in the vehicle or out of the vehicle?
If in the vehicle, using Plastigage will be a major pain in the butt. You’ll have to clean all the oil off of the journal otherwise the Plastigage will dissolve (and it will probably give an erroneous reading to boot). Plus, it’s just not a very precise measurement – you tighten down the bearing cap so it squeezes the Plastigage, remove the bearing cap then compare the width of the crushed Plastigage strip to a printed line on a sheet of paper. It totally sucks.
Anyway, if the engine is in the vehicle, and you can determine if it’s rebuilt or not, using Plastigage for a simple bearing replacement is sort of a moot point because changing the bearing will close up the oil clearance anyway. It still might not be within OE spec, but it should be better than what you started with at the beginning of the job.
If in the vehicle, using Plastigage will be a major pain in the butt. You’ll have to clean all the oil off of the journal otherwise the Plastigage will dissolve (and it will probably give an erroneous reading to boot). Plus, it’s just not a very precise measurement – you tighten down the bearing cap so it squeezes the Plastigage, remove the bearing cap then compare the width of the crushed Plastigage strip to a printed line on a sheet of paper. It totally sucks.
Anyway, if the engine is in the vehicle, and you can determine if it’s rebuilt or not, using Plastigage for a simple bearing replacement is sort of a moot point because changing the bearing will close up the oil clearance anyway. It still might not be within OE spec, but it should be better than what you started with at the beginning of the job.
#17
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Im so confussed right now it rediculous, so if i do use the plastigage where and what am i doin with it? like i get im supossed to see how worn the rods are to see if i need over sized bearings right? and if i dont use it what do i do? jus get the standered bearings and slap em in?
#18
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Im so confussed right now it rediculous, so if i do use the plastigage where and what am i doin with it? like i get im supossed to see how worn the rods are to see if i need over sized bearings right? and if i dont use it what do i do? jus get the standered bearings and slap em in?
Your old bearings will be worn, your crank may be worn some, yours prolly wont be worn so bad you need oversize bearings for what you are doing, unless the moter has been rebuilt in the past and the crank was turned and you need them. The plastiguage should mash down from ,001 - .003.....003 is alowable but alot......I had to do mine I went up to .006 mine still rattles at startup but it a trail jeep so i dont care it was a $300 jeep
#19
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Year: 1989
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Im so confussed right now it rediculous, so if i do use the plastigage where and what am i doin with it? like i get im supossed to see how worn the rods are to see if i need over sized bearings right? and if i dont use it what do i do? jus get the standered bearings and slap em in?
If you haven't already, open up the Plastigage package. There will be a strip of paper in there with lines of varying widths printed on it. This is what you compare the width of the smooshed Plastigage to in order to get the clearance reading.
#20
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I would check it anyway, just put your new bearings in place. take about 1/4 to 1/2 inch of plastiguage lay it across the bearing in the cap. Pot your rod cap in place and torque it down, remove rod cap and measure how much the plastiguage mashes down and compare to the measurements on the paper. wipe down the journal really good so it will be nice and clean. When your ready for the caps final instal coat it down really good with some oil or a touch of gearlube.
Your old bearings will be worn, your crank may be worn some, yours prolly wont be worn so bad you need oversize bearings for what you are doing, unless the moter has been rebuilt in the past and the crank was turned and you need them. The plastiguage should mash down from ,001 - .003.....003 is alowable but alot......I had to do mine I went up to .006 mine still rattles at startup but it a trail jeep so i dont care it was a $300 jeep
Your old bearings will be worn, your crank may be worn some, yours prolly wont be worn so bad you need oversize bearings for what you are doing, unless the moter has been rebuilt in the past and the crank was turned and you need them. The plastiguage should mash down from ,001 - .003.....003 is alowable but alot......I had to do mine I went up to .006 mine still rattles at startup but it a trail jeep so i dont care it was a $300 jeep
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Year: 1989
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this is the part i dont get, i buy new bearings and use the plastigage and if the clearance is too much i need the over sized bearings right? i thought the whole point of the plastigage is to figure out what bearings i need so i might wined up buying two sets of bearings?
The rod oil clearance is on the order of .0015” to .002” so you’re literally splitting hairs. A sheet of standard copier paper is .004” thick.
In your situation, replacing the rod bearings only, the Plastigage is only used to verify the clearance is between .001” and .002”. (This is an extremely rough tolerance, but it’s about the best you can do with Plastigage, and only if you’re very careful with it at that.) If it’s larger or smaller than that there’s not much you can do.
Sometimes you can get away with swapping bearing halves until everything fits. Even though all standard bearings are supposedly the same thickness, they have some manufacturing variance. And, you don’t have to swap the bearings in pairs, it’s okay to use two bearing shells with different thicknesses. You can even swap between the old used ones and new ones. (Not preferred, but better than an out-of-tolerance oil clearance.)
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If you've damaged the engine to the point that you think you may need to go with "oversized" (actually smaller diameter) bearings, you need to get the crank ground before you bother doing anything.
If all you're doing is replacing the bearings with new ones the same size as the existing ones, why bother with the measurement? What are you going to do with that information regardless of how it comes out? Unless you intend to have the crank ground if the clearances are out of spec, slap the new bearings in with some good assembly lube and put it back together.
If all you're doing is replacing the bearings with new ones the same size as the existing ones, why bother with the measurement? What are you going to do with that information regardless of how it comes out? Unless you intend to have the crank ground if the clearances are out of spec, slap the new bearings in with some good assembly lube and put it back together.
#23
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bouts to not even worrie about it, im just going to put the oil pump in and call it good, george said that probably my problem anyways.
#24
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Or atleast drop a bearing cap and see what the bearings look like, if they look new and smooth dont worry about it.
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i just came across this thread , but can you change out the bearings without removing the entire motor??? I mean i have low oil pressure when my jeep warms up and i have a constant tick/rattle and i have been told that its could be either the main and rod bearings, or the cam and cam bearings/lifters.... But i went the cheap route and just replaced the oil pump and it is still doing this so i am faced with this same decision but i am unsure of wat it is exactly, and if i can do it without removing the engine from the vehicle...
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Originally Posted by jpfouts1
i just came across this thread , but can you change out the bearings without removing the entire motor??? I mean i have low oil pressure when my jeep warms up and i have a constant tick/rattle and i have been told that its could be either the main and rod bearings, or the cam and cam bearings/lifters.... But i went the cheap route and just replaced the oil pump and it is still doing this so i am faced with this same decision but i am unsure of wat it is exactly, and if i can do it without removing the engine from the vehicle...
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