main bearing/crankshaft

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bigc19

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Aug 31, 2010
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97
Just got my motor and all back from the machine shop. Im in the process of putting the crank back in, which was polished at the machine shop. Im using standard bearings and installing studs. Im at 160ft lbs and can not spin the crank by hand. I could barely spin it at 130ft lbs with a strap wrench and 18 inch bar. Is it supposed to be this tight, or is something wrong here. I always thought it should be able to be turned by hand. Thanks
 
something is wrong. do you have the main caps switched around? not sure what the torque spec is for the mains but that sounds high.
 
Something is very wrong. You got the main caps in correct order and facing the correct way? Did you check to make sure all the bearings in the box were all stamped standard? If so, I would remove all main caps and install them one at a time and torque them and see when I gets tight. You will probley find your issue. Spec on studs sounds high.
 
The arp instructions are calling for 175. Ill pull it all back off and go one at a time and see what happens.
 
I agree, better check bearing clearance and make sure you dont have the caps backwards.
 
They should be 12 mm, doesnt say on the box, but I wouldnt have spent the extra money on the 14s. Yes, lots of assembly lube. As for the torque number of 125, thats less than factory spec. Factory is 129. To me that doesnt make sense, but I may be wrong on my thinking
 
bigc19 said:
They should be 12 mm, doesnt say on the box, but I wouldnt have spent the extra money on the 14s. Yes, lots of assembly lube. As for the torque number of 125, thats less than factory spec. Factory is 129. To me that doesnt make sense, but I may be wrong on my thinking
Click to expand...

Factory is bolts, torque is different.

I would check the bearings to make sure they are the correct dimension, and obviously check clearance. Plastigage.


Also, why did you have the engine apart? Spun bearing, or anything like that?

Chris
 
Head gasket blew and had 340000 on the motor. I didnt want to just have the head decked and the block be a little out and blow the gasket again. Pulled it, got the head decked and a valve job, honed the walls, decked the block and had o rings cut, and had the rotating assembly balanced. Turns out I could have just got the head decked, but I wanted to be safe than sorry
 
Do the initial torque one cap at a time and spin the crank each time. You'll find your problem this way. The crank should turn easily and smooth with with an even resistance for 360 deg even after all caps are tightened to full torque
 
Im hoping nothings damaged as well. After looking back at what I ordered, theres no indication that the studs are 14mm, so its safe to say theyre 12mm. Im still a little lost on the torque. My instructions that came with the kit say 175, arp website says the same, but it seems all yall who have done this before are running 125. As for if the caps are correct, I honestly am not sure. The fsm says that they should be in order, 1-7, but mine has 2 6s and 2 3s. I think they may have been more random originally. I would assume the only way to put them where they need to be is to plasigage them all? Or could I just torque them one at a time and as long as it spins freely, theyre fine?
 
They all came out of the factory numbered 1-7. Either yours has been replaced in a previous life, or the machine shop got some caps switched around with another block. If you took #125 studs to #175 I'd throw them away and get new ones. Maybe call ARP and ask them about it.
 
In all rights the block should have been line bored with the studs installed and torque bit in any case the numbering goes 1-7 if it isn't someone had their d#co beaters in there before you.
 
Thats the thing, I noticed when I took them off they were numbered like that. I know the machine shop didnt mess them up as it was a small gas shop, and I was the most work theyd ever done to a cummins. Ill have to call arp tomorrow and figure all that out. Now I need to figure out this stupid cap numbering problem. I find it hard getting them mixed up at the factory, and I dont see the motor having been rebuilt previously, but Im not sure how they would be how they are
 
What year is your motor? that will tell us if you have 12mm or 14mm studs.

ARP torque spec for the 14mm is indeed 175 ft lbs, while the 12mm is 125 ft lbs.

Your crank journals should have been line bored while your engine was at the machine shop. That should negate the fact that the caps are miss-matched as long as they were installed in the same position they were line bored at. I would verify the size of the crank bore by removing the crank and installing the caps, and torquing them down a little bit. Use an inside mic or snap guages to check the bore size of the crank journal.

Also, as far as I'm concerned I never assemble a motor without checking clearances with plastiguage. I don't care how many times I have to take that cap back off thats one of the most important measurements.

In short make sure the caps are installed in the correct position that they were line bored in, and the correct direction. I believe the numbers go towards the passenger side oil pan rail, but remember that is reversed when the engine is upsidedown on a stand.
 
Its a 97. Ill be pulling it completely back apart tomorrow and go through everything yall have said and just taking my time getting it right. Even if it takes all day just to get the crank in, as long as it gets done smooth, Im fine with it.
 
bigc19 said:
Its a 97. Ill be pulling it completely back apart tomorrow and go through everything yall have said and just taking my time getting it right. Even if it takes all day just to get the crank in, as long as it gets done smooth, Im fine with it.
Click to expand...

Should be 14mm mains for the old 12v blocks.
 
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