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Unread 04-27-2015, 01:34 AM   #1
agear
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258 engine knock

My remanufactured 258 engine knocks. Do you guys think it's a rod bearing and if so can it be repaired with the engine in the vehicle ? Do you think it's a crankshaft journal bearing thing and if so can the crankshaft be removed with the engine still in the jeep ? I'm thinking it might just be a bearing that needs to be replaced Could it be something with the piston or cylinder ?

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1984 jeep cj7, 258 I6, rebuilt T176,rebuilt Dana 300, amc 20 , dana 30, 4.10's Trac-lok in rear , 4.10's detroit soft locker in dana 30, 2.5 inch bds suspension lift, 1 inch polyurethan body mount lift. Line ex. weber carburetor. factory tach. factory clock ,oem replacement speedomter cluster, and oil pressure gauge, factory volt gauge.
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Unread 04-27-2015, 03:07 AM   #2
cuban11182
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Anything can be repaired with the engine in the vehicle (for the most part), but why not just take back the engine for a replacement. If you make a video and upload it, it might make it easier for us to diagnose.

Best of luck.
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Unread 04-27-2015, 03:26 AM   #3
gmakra
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agear how many miles on the engine? Does the engine knock all the time? Does is go away after the engine warms up?
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Unread 04-27-2015, 01:25 PM   #4
agear
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A guy on here went through 2 marshall remanufactured engines before he got a decent one. And I'm not going through the hassle. The engine is just a couple years old. I'm not sure how many miles-maybe 15,000. As a matter of fact when the engine warms up I can't hear it anymore.
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1984 jeep cj7, 258 I6, rebuilt T176,rebuilt Dana 300, amc 20 , dana 30, 4.10's Trac-lok in rear , 4.10's detroit soft locker in dana 30, 2.5 inch bds suspension lift, 1 inch polyurethan body mount lift. Line ex. weber carburetor. factory tach. factory clock ,oem replacement speedomter cluster, and oil pressure gauge, factory volt gauge.
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Unread 04-27-2015, 02:37 PM   #5
agear
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Okay, I went out there with the stethoscope and could here the knock through the valve cover but not the block at cylinders 4,3,2,1. But I think it was loudest at cylinder 2. Cylinder 3 was second loudest followed by cylinder 4 then 1 then six. I unplugged the spark plug wire 1 at a time and ran the engine each time. The knock didn't go away.
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1984 jeep cj7, 258 I6, rebuilt T176,rebuilt Dana 300, amc 20 , dana 30, 4.10's Trac-lok in rear , 4.10's detroit soft locker in dana 30, 2.5 inch bds suspension lift, 1 inch polyurethan body mount lift. Line ex. weber carburetor. factory tach. factory clock ,oem replacement speedomter cluster, and oil pressure gauge, factory volt gauge.
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Unread 04-27-2015, 04:26 PM   #6
gmakra
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So the noise disappears when the engine is hot?
If that's the case it could be piston slap and its not a big deal.
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Unread 04-27-2015, 04:33 PM   #7
agear
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Yes, I think so. Why is piston slap not a big deal ? What causes it ?
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Unread 04-28-2015, 03:23 AM   #8
gmakra
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Its a matter of geometry were the wrist pin is located at and that the piston grows in diameter after warming up.
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Unread 04-28-2015, 04:39 PM   #9
agear
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I guess if check all the bearings and they're good and so are the wrist pins then the problem is an excessively enlarged or ovate cylinder ?
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Unread 04-28-2015, 06:39 PM   #10
80cj
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Quote:
Originally Posted by gmakra View Post
So the noise disappears when the engine is hot?
If that's the case it could be piston slap and its not a big deal.
Those are the symptoms of piston slap. If it goes away to the point that you can't hear it when it warms up, I wouldn't worry about it. I used to work at a NASA tracking station and we had GSA contract vehicles...Ford Torinos. Several of them sounded like they had piston slap. The sound went away when warmed up and never gave any problems.
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Unread 04-29-2015, 01:55 AM   #11
agear
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Okay. Is it something that can be corrected if I ever rebuild the motor , by like boring it out a little or...... ?
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1984 jeep cj7, 258 I6, rebuilt T176,rebuilt Dana 300, amc 20 , dana 30, 4.10's Trac-lok in rear , 4.10's detroit soft locker in dana 30, 2.5 inch bds suspension lift, 1 inch polyurethan body mount lift. Line ex. weber carburetor. factory tach. factory clock ,oem replacement speedomter cluster, and oil pressure gauge, factory volt gauge.
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Unread 04-29-2015, 02:04 AM   #12
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Okay. Is it something that can be corrected if I ever rebuild the motor , by like boring it out a little or...... ?
Probably. Usually piston slap occurs when the piston fit is slightly out of spec...loose in the bore. Careful final honing and matching pistons to the bore should eliminate or reduce chances of piston slap.
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Unread 04-30-2015, 02:05 PM   #13
agear
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Im planning on doing a head gasket so ill have the head off. anything I can check for with the head off ?
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Unread 04-30-2015, 08:11 PM   #14
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Im planning on doing a head gasket so ill have the head off. anything I can check for with the head off ?
You could mike the bores and check for taper and out of round but you wouldn't be able to get the full cylinder with the pistons in place. I guess if you detected excessive taper or out of round, that would tell you why you have piston slap.
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Unread 05-01-2015, 09:47 AM   #15
mastercraftka
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Could it be the hydraulic lifters? mine knocks when cold, once they get lubed up it goes away, typical.
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