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Old 12-18-2002, 09:17 AM
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Post CONNECTING ROD SLOP

2 Months ago I took my 2.8 liter V6 173CID To the machine shop. I had the block bored .040 over, the crank turned .010/.010. Since I fly around alot fixing airplanes I thought I would save myself some time and let them put some of the block togeather for me. When I went to pick up the engine everything looked good. New pistons,Crank installed, and connecting rods. The thing is I got the engine home and when I was mounting it on the engine stand I started noticeing there was alot of play in the connecting rod to crank mounting clearance. I went to the book and it called out I think .005 for max clearance. So I called the guy up and told him what I found. He said everthing is good trust him. So my question is if the book says says .005 even if the crank was turned and the rods were cut don't you still have to mantain .005 clearance as the max. I have'nt had a chance to measure it becuase I'm on the road alot, but it is always on my mind like the song. it is either .0005 or .005 I can't remember.

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Old 12-18-2002, 10:56 AM
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Take one of the rod caps off and the bearing should say if it is standard or .001 over or something. I would think if the crank was ground and they used standard size bearings then you would have some play. He may have even used the old ones instead of replacing with new ones. I hate it when people do things half ars!

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Old 12-18-2002, 01:56 PM
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if the motor isnt in the car yet take the oil pan off and plasta gadge the main bearings..
go by the engines speck youll have to take it apart any ways to make sure the parts are new and not old and if there even the right ones good luck
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Old 12-19-2002, 05:19 AM
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I think your right nomatter what I'm going to have to take it apart to make sure. The thing that sucks is that I paid the guy $300 to put the bottom end together. If its wrong I'll take it back and make him do it will I stand behind him schooling him.
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Old 12-19-2002, 07:19 AM
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Mike, to get back to your original question: Yes, the clearances should be the same with a reground crank. When the crank is ground, bearings with thicker shells are installed to compensate for the amount ground off of the crank pins. Your spec of .005" is too much for rod bearing clearance though. Think you will find that the recommended clearance is .0015" to .0041". You can get plastigauge at the local NAPA or CarQuest store, it is cheap and you will have the peace of mind knowing for sure what the clearances really are. Good luck and have fun.
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Old 12-19-2002, 05:41 PM
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engine guy hit the nail on the head , you must plastigauge the bearings . really shouldnt be more than .003 clearance .
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Old 12-20-2002, 07:15 AM
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So if I take my two fingures and grab one of side of the connecting rod and wiggle it back and fourth real quick and am able to produce a chatter does that sound right. because my thought would be if I can produce a chatter like that what would it sound like when I started it up. I know that I would have some cushion from the oil until the oil got hot. Then I would lose some clearance when parts start to expand from heat. I will deffinatley check the clearance before I assemble the engine.
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Old 12-20-2002, 08:54 AM
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Mike,
You are correct, clatter is NOT good. Check it out before you go any further on the project.
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Old 12-20-2002, 02:10 PM
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Are you talking about side to side clearance here ( between the 2 rods ) or rod bearing to crank clearance ?
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Old 12-20-2002, 09:17 PM
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[ December 20, 2002: Message edited by: slider ]</p>
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Old 12-20-2002, 09:18 PM
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You know Mike, I would NOT pull a nut or bolt. The motor would go right back to the fella that did the rebuild and I would stand there with a really large wrench or bigger friend while he proved to me the job was done correctly (or not). If you touch a thing you are a had turkey.
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Old 12-21-2002, 09:05 PM
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Hey Mike, I think hdshp has the right question, are you talking about side to side rod clearance, or rod bearing to crank clearance? If you've got enough rod bearing to crank clearance to make a noticable sound you don't need any plasti-gage, you need a new machine shop !!!

[ December 21, 2002: Message edited by: Pinardi ]</p>
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Old 12-22-2002, 02:28 PM
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It's common for the side clearance to increase when you grind a crank. As you sweep across the journal you take a very small amount off of the cheek area of the crank, and alot of shop sand, or grind the sides of the rods just a hair when they re-size them, these two operations will increase the con-rod side clearance. Excessive side clearance is much more forgiving than too much bearing clearance. If you have .005 bearing clearance, you're in big trouble, but if you are just moving the rods from side to side, and you notice some play from side to side, that's normal and shouldn't be a problem.

[ December 23, 2002: Message edited by: NAIRB ]</p>
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Old 12-23-2002, 06:04 AM
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The clearance is connecting rod to crank. The connecting rod clearance is O.K. I'm going home in a couple of days so I will be able to take a better look at it. But there seems to be alot of bearing clearance there.
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Old 12-23-2002, 11:55 AM
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MAYBE I'LL JUST LOAD IT UP AND TAKE IT BACK AND HAVE HIM SHOW ME ITS RIGHT
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