Quote:
A couple of tricks I've used on high tensile bolts.
#1 Oxy/Acet torch with 000 or smaller tip, run it slightly-lean and de-temper the center of the bolt.
Work quickly, only turning the bolt red, spray with penetrant AFTER the fire hazard has cooled.

#2 Plunge-Cut with a 1/4" Air Die Grinder, use a Ball Burr, double cut makes safer shavings, singe cut burrs make HAZARDS!

This works well removing Titanium Pop-Rivets also.
{Electric Die Grinders mis-used in this way are more hazardous than Air driven}

#3 1/4" Die-Grinder with 1/4" "mill-length" drill bit, these are very short, may find them in Cobalt only or Titanium Coated.
Stay away from standard HSS High Speed Steel Bits.
@ 20-30,000 rpm make sure to shield up your arms, chest, all exposed body parts in case of bit breakage.

LH Drill usage, go "slower" than standard speeds, vary up and down, this sometimes will grab the broken fastener.

Does the "Shoulder" of the bolt go fully through the flywheel?

Check the "Fit" between the flywheel and the shoulder OD of the fastener.
Has the gap gotten wider ?

Going back with the larger bolts seems like a good idea if there's enough meat there.

ARP bolts are good for sure, some mfg's of fasteners {Chinese} do not have the consistency of ARP

60 minutes or some other so-called News had a piece on fasteners a few years ago and the Chinese Bolts featured at that time, were inconsistent compared to American Mfg'd bolts. Though to be fair, I do think the Chinese have gotten better at quality control..

I HAVE distributed a few 100,000 bolts in my time at Southern Company and the Grade 5 minimum standard we have implemented on plated std fasteners has eliminated most bolt problems.

Rusty Wrench