Engine bulid
06-18-2019, 04:52 PM
#1
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Model: Cherokee (XJ)
Engine bulid
Looking for technical help. Rebuilding my sons 4.0. The rod and main bearings have a standard half and a .001 half. Finding replacement.001 half’s is next to impossible. My question is will standard for both halves work. If so what is the plastiguage clearance for the rod and mains so I can check to make sure it is not too tight? Please help. Thank you!
06-18-2019, 05:53 PM
#2
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If I am understanding you right, you are saying they mixed a std bearing with a .001 bearing on each journal? If so, you need to find the person who did that and knock some sense into them, physically.
After you do that, please throw the strip of plastigauge in the trash. It is nearly worthless. I would rather you use a digital caliper, which still isnt the right thing to do. You really need to get the correct type of caliper to know what kind of clearances you are dealing with. .001" is a lot when talking about bearing clearances so everything must be precise or you are going to be creating even bigger problems.
Step one - Measure both the rod and main journals on the crank. Compare your measurements to what it should have been from the factory (I dont know what they are off the top of my head. If you have a factory service manual, it will get you the info needed). Technically, you should measure the big end of the rod journals too but chances of the rods being out of spec is slim, unless a bearing spun at one point in time. Are any of the rod caps darker then the others?
If you crank is within the factory spec, you should be able to just get std size bearings and slap them in, again, assuming the rods are fine. If its out of spec, I wouldnt waste your time with .001" bearings as the crank probably needs a polish which will take off at least .001". Just have it turned .010"/.010" and call it a day.
My go to bearing is a Clevite 77. I used them in the last 3 Jeep engines I rebuilt. Rods are #960 and mains are #1947. For the bearings they come in different grades. Example - CB960A is the bottom of the line rod bearing (CB is for rods / MS is for mains). CB960P is the middle of the road. And CB960HN is the race series. I like the P series for daily drivers. If you want me to go in to deeper details on all this, just ask but hopefully this helps.
After you do that, please throw the strip of plastigauge in the trash. It is nearly worthless. I would rather you use a digital caliper, which still isnt the right thing to do. You really need to get the correct type of caliper to know what kind of clearances you are dealing with. .001" is a lot when talking about bearing clearances so everything must be precise or you are going to be creating even bigger problems.
Step one - Measure both the rod and main journals on the crank. Compare your measurements to what it should have been from the factory (I dont know what they are off the top of my head. If you have a factory service manual, it will get you the info needed). Technically, you should measure the big end of the rod journals too but chances of the rods being out of spec is slim, unless a bearing spun at one point in time. Are any of the rod caps darker then the others?
If you crank is within the factory spec, you should be able to just get std size bearings and slap them in, again, assuming the rods are fine. If its out of spec, I wouldnt waste your time with .001" bearings as the crank probably needs a polish which will take off at least .001". Just have it turned .010"/.010" and call it a day.
My go to bearing is a Clevite 77. I used them in the last 3 Jeep engines I rebuilt. Rods are #960 and mains are #1947. For the bearings they come in different grades. Example - CB960A is the bottom of the line rod bearing (CB is for rods / MS is for mains). CB960P is the middle of the road. And CB960HN is the race series. I like the P series for daily drivers. If you want me to go in to deeper details on all this, just ask but hopefully this helps.
06-18-2019, 06:00 PM
#3
Old fart with a wrench
In my experience, most lead babbit bearings are usually .001 to .002 clearance. My book for the 4.0 says rod bearings, .0015 to .002, wear limit .003. Main bearing .002, allowable .001 to .0025. I prefer micrometers for measuring journals. Digital calipers are for barnyard mechanics. I measure them in 4 places 90* from each other, front and back.
Using mismatched shell halves is standard procedure for factory assembly if the crank or rods are out of limits.
5-Speed, you are right about Clevite 77. That's all I've ever used. Good enough for Richard Petty, good enough for me.
Using mismatched shell halves is standard procedure for factory assembly if the crank or rods are out of limits.
5-Speed, you are right about Clevite 77. That's all I've ever used. Good enough for Richard Petty, good enough for me.
Last edited by dave1123; 06-18-2019 at 06:18 PM.
06-21-2019, 06:50 AM
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Rings
5 Speed, what is your choice for rings?
If I am understanding you right, you are saying they mixed a std bearing with a .001 bearing on each journal? If so, you need to find the person who did that and knock some sense into them, physically.
After you do that, please throw the strip of plastigauge in the trash. It is nearly worthless. I would rather you use a digital caliper, which still isnt the right thing to do. You really need to get the correct type of caliper to know what kind of clearances you are dealing with. .001" is a lot when talking about bearing clearances so everything must be precise or you are going to be creating even bigger problems.
Step one - Measure both the rod and main journals on the crank. Compare your measurements to what it should have been from the factory (I dont know what they are off the top of my head. If you have a factory service manual, it will get you the info needed). Technically, you should measure the big end of the rod journals too but chances of the rods being out of spec is slim, unless a bearing spun at one point in time. Are any of the rod caps darker then the others?
If you crank is within the factory spec, you should be able to just get std size bearings and slap them in, again, assuming the rods are fine. If its out of spec, I wouldnt waste your time with .001" bearings as the crank probably needs a polish which will take off at least .001". Just have it turned .010"/.010" and call it a day.
My go to bearing is a Clevite 77. I used them in the last 3 Jeep engines I rebuilt. Rods are #960 and mains are #1947. For the bearings they come in different grades. Example - CB960A is the bottom of the line rod bearing (CB is for rods / MS is for mains). CB960P is the middle of the road. And CB960HN is the race series. I like the P series for daily drivers. If you want me to go in to deeper details on all this, just ask but hopefully this helps.
After you do that, please throw the strip of plastigauge in the trash. It is nearly worthless. I would rather you use a digital caliper, which still isnt the right thing to do. You really need to get the correct type of caliper to know what kind of clearances you are dealing with. .001" is a lot when talking about bearing clearances so everything must be precise or you are going to be creating even bigger problems.
Step one - Measure both the rod and main journals on the crank. Compare your measurements to what it should have been from the factory (I dont know what they are off the top of my head. If you have a factory service manual, it will get you the info needed). Technically, you should measure the big end of the rod journals too but chances of the rods being out of spec is slim, unless a bearing spun at one point in time. Are any of the rod caps darker then the others?
If you crank is within the factory spec, you should be able to just get std size bearings and slap them in, again, assuming the rods are fine. If its out of spec, I wouldnt waste your time with .001" bearings as the crank probably needs a polish which will take off at least .001". Just have it turned .010"/.010" and call it a day.
My go to bearing is a Clevite 77. I used them in the last 3 Jeep engines I rebuilt. Rods are #960 and mains are #1947. For the bearings they come in different grades. Example - CB960A is the bottom of the line rod bearing (CB is for rods / MS is for mains). CB960P is the middle of the road. And CB960HN is the race series. I like the P series for daily drivers. If you want me to go in to deeper details on all this, just ask but hopefully this helps.
06-21-2019, 04:53 PM
#6
Old fart with a wrench
I've never had experience with Totalseal, but I know Hasting and have used them before. Perfect Circle was my dad's go to.
06-21-2019, 05:09 PM
#7
CF Veteran
The most important thing is to stay away from "chrome" rings. They are way too hard and eat cylinder walls. I like the plasma moly or steel nitride ones better. Ductile iron works great in lower HP engines too and are cost effective. Lots of choices out there.
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