--Mike
grinding noise
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grinding noise
fellas i need some help
just finished a rebuild on a 390 put a few HiPo mods in it and have it purrin' real nice. my problem is i hear a bit of grinding (i think) when i push the clutch in. you can actually see the crank move about a 1/4 of an inch while pushing on the clutch. i imagine the noise are my rods getting tourqed at a funny angle, and any advice on how to fix this without tearing the engine apart would be appreciated.
just finished a rebuild on a 390 put a few HiPo mods in it and have it purrin' real nice. my problem is i hear a bit of grinding (i think) when i push the clutch in. you can actually see the crank move about a 1/4 of an inch while pushing on the clutch. i imagine the noise are my rods getting tourqed at a funny angle, and any advice on how to fix this without tearing the engine apart would be appreciated.
Posting Guru
Joined: Jul 2003
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From: Colville, Washington
There is no way to fix it without tearing the crank out. The thrust surface of the crank or #3 main bearing is worn-badly. The crank should only move .004-.010", yes thats 4-10 THOUSANDTHS of an inch.
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there is only about an hours worth of actual running time on the motor so far. did i completely screw up the rebuild or is there any other possibility? the crank had to be reground, could the machinist messed up? if it is the crank thrust surface, is it now junk?
Lead Driver
Joined: Jan 2003
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From: Ohio
Well, it's definitely MAJOR problems.
Sounds like you might have had it too tight, in which it wore prematurely trying to make room for itself. You actually are not at fault, unless the fact you did not check it. After putting the caps on, did you "seat" the thrust bearing by tapping each way on the crankshaft? This "squares" the bearing and makes sure it is not twisted. You should have then used a dial indicator to measure how much the crank moves forward/backward to make sure it was within specs. That aside, it may have only worn the bearing surface and not hurt the crank yet. Only thing to do is pull it down and check the damage. If you're lucky, a new set of bearings will fix it. Keep your fingers crossed.
I would definitely double check the next one. Usually all the ones I have done are a bit on the loose side(maybe .012), but never have been too tight.
Good Luck
Sounds like you might have had it too tight, in which it wore prematurely trying to make room for itself. You actually are not at fault, unless the fact you did not check it. After putting the caps on, did you "seat" the thrust bearing by tapping each way on the crankshaft? This "squares" the bearing and makes sure it is not twisted. You should have then used a dial indicator to measure how much the crank moves forward/backward to make sure it was within specs. That aside, it may have only worn the bearing surface and not hurt the crank yet. Only thing to do is pull it down and check the damage. If you're lucky, a new set of bearings will fix it. Keep your fingers crossed.
I would definitely double check the next one. Usually all the ones I have done are a bit on the loose side(maybe .012), but never have been too tight.
Good Luck
Post Fiend
Joined: Feb 2001
Posts: 6,624
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From: Missouri
I replaced a crank in a 289 once where I could move it back and forth by hand. It was an automatic though. The real funny thing was is that the thrust bearing didn't look damaged at all but the crank had a huge gash cut in it.
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From: Iowa
Originally Posted by Ratsmoker
I replaced a crank in a 289 once where I could move it back and forth by hand. It was an automatic though. The real funny thing was is that the thrust bearing didn't look damaged at all but the crank had a huge gash cut in it.
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Post Fiend
Joined: Feb 2001
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From: Missouri
The only thing I could figure is that the last guy who rebuilt the 289 (it had TRW flattops in it when I took it apart) used an already bad crank with a new bearing. I just don't see how a bearing can eat into a crank without eating itself up. In order to cause abrasion it needs to be abrasive. Weird. I am going to stop thinking about it before I get a headache.
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thanks for the help. i must have missed the section on setting the thrust bearing in the chilton manual. i guess my only option now is to pull out the crank, pray it's not damaged, and try again. if i have any other options let me know. until then i'll be yanking that engine out.
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