Tightening the short bolts of main bearing caps.

[valyidol]

Hi everybody!
Two days ago I was given a 6.5 diesel with a broken crankshaft for repair. 97 Chevy Suburban. The first time I saw thin bolts on the crankshaft bearing caps. Thin short bolts are on the second, third and fourth main bearing caps. Tell me please, how do I need to tighten them?

 

[NVW]

They are 30 ft/lbs or 40 N-Meter

 

[valyidol]

Wow! Realy? Only 40 N/m. Wy that?

 

[Will L.]

Small diameter will strip the threads out if more.

Inspect the main webs for cracks while your there.

 

[valyidol]

Oh sure! But why did they make small diameter?

 

[Will L.]

The main webs crack because of poor metallurgy used and the larger diameter bolts leave too little metal around it causing cracks to occur sooner. Later with the Optimizer this was corrected.

 

[valyidol]

OK. Thank you!

 

[valyidol]

I made a crankshaft girdle and studs for that and for heads. Somebody tell me pls what tightening studs 12mm and 10mm. What tightening heads studs?

 

[valyidol]

https://drive.google.com/open?id=0B5CwxafH55kHOG00Vy03ZEVoa3M

 

[valyidol]

I tightened studs 126 N/m. The studs not are tightened any more they only springs. Is it anough?

 

[ak diesel driver]

126nm=92 ft lbs was supposed to be 40 ft lbs. I'd say they're more than tight

 

[valyidol]

126 N/m = 12mm studs

 

[valyidol]

10mm studs = 40 N/m

 

[valyidol]

My question is about 12 mm studs and about the cylinder head studs like to ARP

 

[Will L.]

The arp head studs are 130 ftlbs. Using 30wt oil to lube threads. 90ftlbs if useing a moly lube.

On your mains you need to read the clearance of bearings usings plastigauge or something similar. Then retorque to the same amount. Your current torque is WAY TOO MUCH. Youll pull out threads once the load of the engine running is there.

Your main studs torque will be different than regular because of the space you added with your girdle you made -which i dont see helping - ive tried several types of main gidles. You need to do the equations on torque based on what your geometry of the girdle you designed. Using too low of torque will let them come loose or chatter the bearings. Too much will pull out the threads... Just adding a girdle because it looks cool can cost you an engine. Its like drilling holes in the connecting rods to make them light wieght. If your lucky it might help 3%, if not lucky your engine will bcome a grenade. Good luck.

 

[valyidol]

In manual the short main bolt torque is 136 N/m. I plan to tighten the nut 12 mm 136 N / m. But the studs are tightened weaker than nuts. Is there normal? I have made studs from very strong steel and tempered them. Drawing girdle from here: http://www.thetruckstop.us/forum/attachments/girdle-jpg.40540/
This diesel has very bed histori. Three cracked cranckshafts. Look it:

 

[valyidol]

I milled plane crankshaft bearing caps and drilled a hole for the crankshaft.

 

[valyidol]

I installed SCAT cranckshaft. But I afraid. I want to be sure that it will not crack crankshaft any more.

 

[valyidol]

On this diesel all holes of short main bolts are 12mm. Next diesel waiting assembly has 10 and 12mm holes. I made two pair girdles and two sets of studs.

 

[ak diesel driver]

IIRC the guys doing those hand file fitted the girdles to get the tolerances really close. Are you align honing the block?