Engine rebuild advice
03-15-2012, 09:32 AM
#1
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Year: 1993
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Engine: 4.0
Engine rebuild advice
So i have my spare engine sitting in the shop and i'd like to do a mild rebuild on it. If the crankshaft is good, i'll stick with that but basically i just want a dependable motor that doesnt make any damn noises that it's not suppose to. Can i keep the crank, rods, and pistons and just swap out all the bearings and rings? I'll probably have the block dipped and honed too. I'm also thinking of throwing in a performance camshaft so if anyone knows a good one, let me know. I guess i'm just looking to see if anyone else has rebuilt thier motor without breaking the bank. Thanks
03-15-2012, 10:02 AM
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Year: 90,84
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Engine: 4.0,2.5
You gotta hone anytime you install new rings so they can seat. Usually you want to remove the ring ridge before honing. No big deal. (to rent the ring ridge remover along with the hone).
On a couple JY engines I just stuck in new rod inserts in on GP since it's so easy & cheap with the engine out. Re ringing is not a bad idea, just don't get carried away honing. Cylinder wear and taper. (a little misleading since they get larger below), wear and taper is the killer there and honing you are taking a little more off. (big enough and piston slap turns to piston "bang")
You can get an idea of taper by putting a ring in the bore near the top, (below the ridge, which hopefully you don't have!), and measure the end gap with a feeler gauge, then do the same lower and compare. Really you might want a manual. So, yes, you can use the original pistons if your taper isn't so bad you need to have the block bored and go with oversize pistons.
(^Generally^)
On a couple JY engines I just stuck in new rod inserts in on GP since it's so easy & cheap with the engine out. Re ringing is not a bad idea, just don't get carried away honing. Cylinder wear and taper. (a little misleading since they get larger below), wear and taper is the killer there and honing you are taking a little more off. (big enough and piston slap turns to piston "bang")
You can get an idea of taper by putting a ring in the bore near the top, (below the ridge, which hopefully you don't have!), and measure the end gap with a feeler gauge, then do the same lower and compare. Really you might want a manual. So, yes, you can use the original pistons if your taper isn't so bad you need to have the block bored and go with oversize pistons.
(^Generally^)
Last edited by DFlintstone; 03-15-2012 at 10:13 AM. Reason: Generally
03-15-2012, 11:06 AM
#4
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Year: 1990
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Rent an outside micrometer. What's the limit on taper don .006? If there is too much taper the rings will have to expand and contract too much and will quickly lose seal.
03-15-2012, 11:20 AM
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Year: 1993
Model: Cherokee
Engine: 4.0
You gotta hone anytime you install new rings so they can seat. Usually you want to remove the ring ridge before honing. No big deal. (to rent the ring ridge remover along with the hone).
On a couple JY engines I just stuck in new rod inserts in on GP since it's so easy & cheap with the engine out. Re ringing is not a bad idea, just don't get carried away honing. Cylinder wear and taper. (a little misleading since they get larger below), wear and taper is the killer there and honing you are taking a little more off. (big enough and piston slap turns to piston "bang")
You can get an idea of taper by putting a ring in the bore near the top, (below the ridge, which hopefully you don't have!), and measure the end gap with a feeler gauge, then do the same lower and compare. Really you might want a manual. So, yes, you can use the original pistons if your taper isn't so bad you need to have the block bored and go with oversize pistons.
(^Generally^)
On a couple JY engines I just stuck in new rod inserts in on GP since it's so easy & cheap with the engine out. Re ringing is not a bad idea, just don't get carried away honing. Cylinder wear and taper. (a little misleading since they get larger below), wear and taper is the killer there and honing you are taking a little more off. (big enough and piston slap turns to piston "bang")
You can get an idea of taper by putting a ring in the bore near the top, (below the ridge, which hopefully you don't have!), and measure the end gap with a feeler gauge, then do the same lower and compare. Really you might want a manual. So, yes, you can use the original pistons if your taper isn't so bad you need to have the block bored and go with oversize pistons.
(^Generally^)
03-15-2012, 11:33 AM
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Dude you could just drop the pan and slap a new set of bearings in the current engine. 99% the noise is either rod knock or piston slap. Clap your hands quietly in time with the noise. If it matches up its the piston. If its deeper its rod. If the thing runs good pull the pan and all the plugs and carefully change out the bearings. Plastigauge it to check the clearance. Should be ~.005. Bearings are cheap and you need em anyways. If the clearance is >.008 its excessive. Thing is if your oil pressure is decent chances are a new set of rod bearings will do the trick. Mechanics used to do rods mains and rings without pulling the engine all the time. It's called an in frame. Popular with fleet vehicles or used to be before labor went through the roof. Oh ya if you do this you can build a stroker with the other block. Take your time and do it right I.e. bore it with a torque plate and have it line honed, grind the crank and get new rods, have everything balanced. That's what I would do. My .02
Last edited by Slick761; 03-15-2012 at 11:51 AM.
03-15-2012, 12:27 PM
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Year: 90,84
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BOD, First off you are gonna want to get familiar with plstagauge. On their page there is a little link on the bottom "how it works". Shooten for 2 or three thou would be nice. (if it's up at 5, sell it to Slick! Lol.)
A big issue with the rod journal on the crank is, is it round. You defiantly want to go with the round kind. Once or twice I've found the ovule type doesn't work out so well.
This guy in this thread seems to have gotten by with some questionable clearance. Idk exactly...anyway he said his oil pump did indeed fail...
Plastagauge link is in there somewhere as well>>> https://www.cherokeeforum.com/f2/met...il-pan-124867/
Last edited by DFlintstone; 03-15-2012 at 01:51 PM. Reason: guy in
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03-15-2012, 12:35 PM
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Yes inside Mic..... I like 4 to 5... I like to run a little looser clearance especially in mains. Thing is though on a worn in crank journal 5 is not bad. If its knocking its prob on the high side of 6-7 now. All im saying is you will not get a factory spec without having the journals ground. Don guess it comes down to personnal preference. By the book it is 3-5... I like to run the ragged edge of things so..... If I were building a motor for power I would always run on the loose side for the extra power. How about this... No more then .005 clearance... Fair compromise? :gunsmile:
03-15-2012, 12:46 PM
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You're right I'm wrong. Been a long time since I've done it..005 is too much..003 is $.... Where did I come up with .005.....
Last edited by Slick761; 03-15-2012 at 12:58 PM.
03-15-2012, 01:49 PM
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It's all good.
, WAS talking about rods, don't really know what you might get away with, with mains. Oil pressure would be an issue Imo. Anyway , agreed. Just because shop time, (and there insurance), is so high doesn't mean that I myself don't have time to put brushes in a alternator or bearings or bushings or seals (rings) in something that's shot. That hasn't left me time to finish the wheel balancer though. 
, WAS talking about rods, don't really know what you might get away with, with mains. Oil pressure would be an issue Imo. Anyway , agreed. Just because shop time, (and there insurance), is so high doesn't mean that I myself don't have time to put brushes in a alternator or bearings or bushings or seals (rings) in something that's shot. That hasn't left me time to finish the wheel balancer though.
03-15-2012, 01:54 PM
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Year: 1993
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Dude you could just drop the pan and slap a new set of bearings in the current engine. 99% the noise is either rod knock or piston slap. Clap your hands quietly in time with the noise. If it matches up its the piston. If its deeper its rod. If the thing runs good pull the pan and all the plugs and carefully change out the bearings. Plastigauge it to check the clearance. Should be ~.005. Bearings are cheap and you need em anyways. If the clearance is >.008 its excessive. Thing is if your oil pressure is decent chances are a new set of rod bearings will do the trick. Mechanics used to do rods mains and rings without pulling the engine all the time. It's called an in frame. Popular with fleet vehicles or used to be before labor went through the roof. Oh ya if you do this you can build a stroker with the other block. Take your time and do it right I.e. bore it with a torque plate and have it line honed, grind the crank and get new rods, have everything balanced. That's what I would do. My .02
Yeah i always have good oil pressure and otherwise she runs like new. I had the spare so i could build a stoker but these bearings kinda took the wind outta that lol. I kinda figured it's pretty straight forward replacing just the rod bearings. thats what i'll do then. How do i know what size bearings to order? Should i just get standard size, undersize, ect..?
03-15-2012, 02:06 PM
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BOD, I just listened to that Vid. I might lean toward a lifter, Idk. How many miles on that anyway? Oil pressure? Also be sure to go ahead and check the bolts holding the torque converter. Guess they are known to loosen and can make a real racket. 5 min. job, there under the little dust cover on the bellhousing.
03-15-2012, 02:12 PM
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Whoops! (both typing). You gotta pull one bearing insert and look at the back.
If you look through that thread I posted you can see the process. Yea, I think I saw them for $20 at rockauto...maybe $100 and one truly miserable day will get you some more K's.
If you look through that thread I posted you can see the process. Yea, I think I saw them for $20 at rockauto...maybe $100 and one truly miserable day will get you some more K's.
03-15-2012, 02:25 PM
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Yeah, miserable days with my XJ just make the fun ones all that more fun haha. I already checked the flywheel and converter bolts. They were all tight and the flywheel looked to be ok. I just did a seafoam treatment to see if it would help considering it is said to "help free stuck lifters" but the noise is still there. I'm going to do a compression test after an oil change tonight. I'll let you know what the #s are. If the rings are good i'm just gonna take a saturday and replace those bearings.