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Unread 01-22-2013, 12:52 AM   #1
Greekcj5
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Rebuilt AMC 304 crank won't turn manually

Hey ladies and gents. Here's the jist. I have a 72 AMC 304 that I just had honed, had the crank turned to .020 and installing new main and rod bearings. I got the .020 bearings and installed them with a ton of assembly lube. The problem is when I torque the 1,2,3,4 rod end caps and try to turn the crank to torque 5,6,7,8 it won't budge. If I loosen 3 of 4 caps it turns easily. I'm positive the pistons are in the right cylinders and facing the right way. Is this normal or should I be worried about something else? Thanks

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Unread 01-22-2013, 06:34 AM   #2
roboto65
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Need to get some plastigauge and check your clearances just because the bearing says one thing does not mean it is so it is best to check before assembly. I bet one of the bearings is binding down and that in turn locks the crank down it happens. When I do engines I always check the clearances not knocking the machine shop but we are human.
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Unread 01-22-2013, 06:40 AM   #3
Matt1981CJ7
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Have you checked the connecting rod side-to-side endplay?

Did you check the bearing tolerances with plasti-gauge?

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Unread 01-22-2013, 06:49 AM   #4
timgr
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Yes, measure everything you can - don't assume that the shop did everything right.

Did you assemble the crank in the block without the rods? That assembly should turn freely, and you can Plastigage the mains. Then assemble the pistons and rods one by one and Plastigage.
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Unread 01-22-2013, 06:57 AM   #5
Matt1981CJ7
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When properly installed, the entire assembly should turn smoothly with moderate effort using a 3/4" wrench, or socket on the crank's end bolt.

Matt
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Unread 01-22-2013, 07:37 AM   #6
Greekcj5
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I didn't measure end gaps because I'm reinstalling the same crank and rods. I'll get some plasti-gage and measure them. Is it possible the crank is just a bit bigger than the rod guides and it just needs to be worn in?
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Unread 01-22-2013, 07:49 AM   #7
Matt1981CJ7
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Not likely. If it's binding at all, there is a problem, and it will likely cause fire-up problems, or worse. I learned that lesson the hard way....

My heads had residual glass bead dust in them, that wasn't cleaned out properly before reassembly. This caused to much friction between the pistons and the cylinder walls. Although my crank assembly would turn manually, it took a considerable amount of force to do it. My first fire-up attempt, at the dyno shop, was a complete bust due to this condition. The engine wouldn't spin fast enough to fire. It cost me another $800 to have the dyno shop diagnose and correct the problem.

Hope this helps,

Matt
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Unread 01-22-2013, 08:13 AM   #8
Greekcj5
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Ok so plasti-gauge the rod ends for side to side gaps. Should i worry about the crank end gap? I already rtv'd and installed the timing cover and water pump.
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Unread 01-22-2013, 08:17 AM   #9
CSP
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Plasti-gauge isn't for side to side gaps. It's for the clearance between the bearing and the journals, both main and piston.

And yes, you should worry about the end play of the crank.

This makes me wonder what else you've missed in the assembly.
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Unread 01-22-2013, 08:17 AM   #10
Greekcj5
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Quote:
Originally Posted by timgr View Post
Did you assemble the crank in the block without the rods?
Yes. I got as much done on the engine as i could while i was waiting for the new piston rings.
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Unread 01-22-2013, 08:23 AM   #11
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The only reason i didn't check end play out rod end gap is cause that's the word i got from the machinist who honed the block and turned the crank. It's my first rebuild and everything else has been done according to specs. Ring gap, timing, timing chain play allowance etc. i just started with the pistons last night so plasti-gauging the rod ends can still be done. What if the gaps are too small?
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Unread 01-22-2013, 08:26 AM   #12
Matt1981CJ7
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As CSP stated, you use plasti-gauge to check bearing clearances. A feeler gauge is used to check endplay.

Please tell me you are using a manual, of some sort, to do this overhaul.

Matt
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Unread 01-22-2013, 08:27 AM   #13
82JeepCJ7
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Just a thought.... bearing caps mixed up, installed backwards?
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Unread 01-22-2013, 08:48 AM   #14
Greekcj5
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Quote:
Originally Posted by Matt1981CJ7 View Post

Please tell me you are using a manual, of some sort, to do this overhaul.

Matt
Yeah. I'm using a Chilton manual. I'm mechanically inclined but mostly on helicopters.. I do all our auto maintenance, I've just never been this deep. Its fun so far, i just wanna do it right. Thank u all so far.
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Unread 01-22-2013, 08:55 AM   #15
Greekcj5
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Quote:
Originally Posted by 82JeepCJ7 View Post
Just a thought.... bearing caps mixed up, installed backwards?
I wish it was as simple as that. I double and triple checked them all.
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