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| line honing- crank turning needed? https://slantsix.org/forum/viewtopic.php?t=16367 |
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| Author: | sick6 [ Tue Feb 28, 2006 4:42 am ] |
| Post subject: | line honing- crank turning needed? |
1975 225, forged crank. got the whole thing at the machine shop right now, problem is when you set the crank on the bearings loose it wont turn freely. we took the cank off and stuck it on the lathe, and found it to be true within .002. we took a known straight edge to the mains, laid it across all four, and could not get a .002 feeler through underneath (or any other for that matter). I am not sure what the problem is, it just doesn't want to spin freely sitting on the bearings (just the mains, not with the caps yet). bearings are clevite 77 at .092 thick. assembled the main cap with bearings on the 1 area (without crank to check how round it was), and it was within .003, I am told this was normal also for oil. line machining the block is $200 and turning the crank is $155, I'd like to avoid the cost if I can. any suggestions? |
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| Author: | Charrlie_S [ Tue Feb 28, 2006 5:13 am ] |
| Post subject: | |
Might seem like a stupid question, but, are the bearings the correct ones for the crank? IE: crank standard and bearing standard, not crank standard, and bearing .010 under. |
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| Author: | dusty7t4 [ Tue Feb 28, 2006 5:43 am ] |
| Post subject: | |
I thought .092 was standard, did mother ever make a oversized crank? -dave |
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| Author: | zooter86 [ Tue Feb 28, 2006 7:01 am ] |
| Post subject: | |
use a micrometer & measure the diameter of your crank journals, then bolt & torque the caps back on the motor & measure the bore of the holes. Compare these numbers & make sure you have the right bearings. |
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| Author: | Charrlie_S [ Tue Feb 28, 2006 8:54 am ] |
| Post subject: | |
Hell, just look on the back side of the bearing. If it is under size it will be marked. Then mick the crank. If these parts are at the machine shop, your machinest should be able to determine the problem. Did this crank come out of this engine? Did it turn freely before it was dissambled? I don't understand where you are getting the .092 number. If that is the thickness of the bearing, that is not the correct way to measure. You install the bearoing shell in the engine and torque the main caps. Then measure the diameter of the bearing with a bore gauge. Then measure the diameter of the crank journal, and subtract the difference. The crank should be smaller the the bearing by .0005-.0015 (factory), I have run as much as .0025 in a race motor. |
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| Author: | sick6 [ Tue Feb 28, 2006 2:03 pm ] |
| Post subject: | |
both charlie and zooter, I did try that (bore gauge and measuring journals). that is what makes this so frustrating, everything measures out fine. the old bearing size is even the same thickness as the new ones. the bearing is marked as a standard. I am thinking the crank may be out, even thought it still measures true within .002, only because it sat on its side for a long time...... it is the original crank, ...as in never had anything done to it. HOWEVER, if you could point me to a decoder for the engine block stamp I would really appreciate it. that should shed some light on this. |
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| Author: | slantzilla [ Tue Feb 28, 2006 6:23 pm ] |
| Post subject: | |
Before you do anything, put the bearings in the block with oil in them, the crank in the bearings, and torque the caps down. THEN check and see if it turns or not. The way you are doing it is worse than shadetree.  When you don't know where the problem is, or even if there is a problem, always go back to square one and eliminate evrything possible. 
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| Author: | Pierre [ Tue Feb 28, 2006 6:26 pm ] |
| Post subject: | |
And yes bearing caps ARE directional, even though they may fit both ways. Don't ask me how I found that one out..... |
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| Author: | sick6 [ Wed Mar 01, 2006 2:07 pm ] |
| Post subject: | |
shadetree? I don't know what that is. anyway, I will try it the next chance I get to go down there. right now I found out that its much cheaper to buy new con rods than have the ones I own recondition and all that. figures. |
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