weird problem not chevy - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 6 (permalink) Old Aug 20th, 02, 10:52 AM Thread Starter
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Jeff
 
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ok, i know this isnt about a chevy but we need some help, my friend has a 68 amc amx with a 390 ci engine,when he got the car the engine ran but had a rod knock, so we took the engine out, we had the crank cut .010 on the mains and .020 on the rods, had the rods resized with new bolts and the block was bored .040 over.ok bare with me! on the amc engine the thrust bearing is on the center cap or the #3 cap, when we torqe that cap down to 100 ft lb the crank will not turn. loosen up on the cap and it spins fine. checked the bearings to make sure they were .010 and they are,it only gets tight when we torqe the thrust bearing all others are fine? so we plasti gauged it, all bearings were ok around .0015 the thrust one was .001 or smaller? our next thing was to have the block line bored, we figured that would solve our problem, but it didn't same thing happened. we bought the crank back to the machine shop and they said it was fine and measured out fine. anyone ever have a problem like this, what could be the problem is it posible that the bearing could be defective. oh and its not tight on the thrust part either? help.

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post #2 of 6 (permalink) Old Aug 20th, 02, 11:03 AM
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Don
 
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Sounds like the crank is bent.

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post #3 of 6 (permalink) Old Aug 20th, 02, 02:47 PM
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Could be a side clearance issue on the thrust bearing.

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post #4 of 6 (permalink) Old Aug 20th, 02, 04:43 PM
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David Pozzi
 
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Check the edges of the bearings. If the crank was turned and the crank throw radius is a larger radius than before, the edges of the bearings will have to be narrowed to fit.
David

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post #5 of 6 (permalink) Old Aug 21st, 02, 12:54 AM
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Before putting block assy back together, be sure to use the long skinny rifle barrel brushes to clean out the oil passages, with soap and hot water, to remove metal shavings and other stuff. It would be a pity to assemble and crank it up only to have the bearings go bad due to trash being pumped through them. Where else is the stuff going to go?

Another technique you might do is to clean all the journals & bearings. Coat the journals with Machinist's Bluing. Make sure there is no foreign mat'l between the bearing and its saddle in the block. Place the crank into position in the block. Tighten the bolts. Remove the crank. Check for bluing on the bearing shells, this is where its touching (binding). As David suggested, it may be the journal radii too big. Clean the machinist's bluing from parts using alcohol and a lint-free rag.

Put crank on V-blocks and dial indicator on center bearing journal and rotate crank to check for run-out. Should be no run-out.

A '68 AMX, nice ride. Been looking for a '69 to fix.

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post #6 of 6 (permalink) Old Aug 21st, 02, 10:50 AM Thread Starter
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thanks guys, i'm gonna go over this with a fine tooth comb and try to figure it out, i told him to stick with chevy lol. also we put the crank in another 390 block and it would spin, but kind of tight for my liking, i think dave might be on to something i'm gonna check the edges on those bearings thanx.

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