I've got a 30 year old 5 hp 4 stroke Briggs flathead. The muffler rotted out again. It uses about 1 1/2" 3/8" dia shoulder bolts with a 1/4-20 tip. One bolt broke free the other snapped/seized. Upon closer inspection the same bolt had seized/snapped last time too because I found a 4 quadrant scooping out of the aluminum such as one would do to get access to a stub for vice grips plus heat/wd. Have vague recollection of doing that. This time it snapped at the surface, at the bottom of the scooped depression so no repeats on that procedure. I decide to do nut plus mig welder - weld bolt tip/top to inside of nut, torque on nut. 6x failure!!! So I'm relegated to drilling out on center - my tiny drill bits refused to bite. Even the center punch divot seemed shallow. So I went up 3 different drill sizes till the drill bit could take the necessary pressure to bite without threatening to snap like spaghetti. Bonus, now my hole wandered off center. Using good cutting oil.
There was a tiny amount of galvanise white that came off the nuts. 3 of them went full red thru mask. Is there a chance I hardened the crap out of the bolt welding onto it? Maybe the not-biting drill bits work hardened the hole surface. Maybe I'm getting old and feeble. Maybe the cylinder heat heat pattern pushes one to seizure and not the other?
? ideas?
Off center isn't necessarily a failure sentence. If it's mild you turn the bolt remainder into a crescent and lose some thread on one side. Not great but workable for low load situation.
I'm going to resume the drill fight tomorrow. Blowing it and re-engining - no thanks.
There was a tiny amount of galvanise white that came off the nuts. 3 of them went full red thru mask. Is there a chance I hardened the crap out of the bolt welding onto it? Maybe the not-biting drill bits work hardened the hole surface. Maybe I'm getting old and feeble. Maybe the cylinder heat heat pattern pushes one to seizure and not the other?
? ideas?
Off center isn't necessarily a failure sentence. If it's mild you turn the bolt remainder into a crescent and lose some thread on one side. Not great but workable for low load situation.
I'm going to resume the drill fight tomorrow. Blowing it and re-engining - no thanks.
