Sorry for so many issues!
My 455 main cap bolts are not feeling right as I torque them down. They all acted the same up through 100 lbs with the 2 rears tightening up more quickly. Then trying to move up to 120 on all, the 2 rears hit it with very little rotation. The forward 8 bolts, most hit 120 ok but 2 or 3 won't go past 112-115 and turned almost a quarter turn with no increase. I have a light 10w40 oil on threads and under the head. I'm scared to go any more. Think these factory bolts have "yielded"? Maybe get a new set?

 

Check your bolts for “hourglassing”. I suspect that they are stretched. It might be time for some new hardware.

 

Paul,
Another possibility is that the cast iron tapped threads are yielding. With factory bolts this is more common than the bolts yielding.
This can happen if using a bolt lube with more "slipperiness" than the factory-prescribed lube.
If your lube is a synthetic oil, that would be an example.
Even if this happens, the block is not junk. You would buy and install thread savers which renew the grip.
Gary

 

Thanks Gary, that is also a very viable possibility. Regardless, I’d appreciate it if you could share your findings for general experience purposes Paul. Thanks much.😃

 

I happen to have a spare 455 block here so I torqued it up on the floor - similar spongy feeling on the 4 front caps but they all made it to 120. I'll swap these main bolts over to my build and see what happens. I loosened all on my first block and checked for visible issues - don't see hourglassing or bits of shavings on the threads. But I did not get the usual "crack" when breaking them free initially - think I have them simply oiled too much? This is embarrassing

 

Just to be sure a previous Bubba hasn't pranked me - all 10 main cap bolts are identical, right? Even though the rear cap is shorter and get a ton more thread engagement, the front 8 taller caps use the same bolts and only use half the threads, correct?

 

Don’t go from 100 to 120. You need a bigger spread than that for accuracy.

 

Also . . . . are you certain that your torque wrench is correct ?

 

Good point. It is a relatively new Craftsman 1/2" digital unit. Reviews were all good.

 

Might be worth borrowing one to compare it to. Personally I am not a big fan of digital torque wrenches but thats just me.

 

All is resolved but could have been a combination of things. I switched the main cap bolts from the other block, cleaned up most of the extra oils on threads and under bolt heads, torqued in a broader sequence (50, 75, 100, 120 vs 40, 60, 80, 100, 120). All bolts felt good and hit the numbers. Thanks for the help