It's been 10 days and several hundred miles since the last
bolt shear and I am beginning to hope that the problem has been
solved or at least minimized. I would like to thank all that
responded with suggestions, unfortuneatly I've again
demonstrated my e-mail competence by allowing the replies to
delete from my "old mail" basket so I can't identify you by
name, but thanks to "You know who you are"!
The suggestions were as follows:
Bonnet making contact with air cleaner
-check engine mounts
-check for contact by putting grease/paint/clay on air
cleaner and looking for transfer to bonnet
-check for contact by looking for scrapes or dimples on
bonnet
Bolts overtorqued
Heli coil threads and go back to $14 OEM bolt and rubber washer
Manufacture own shoulder bolt for less than $14
Check that bolts are not too long and bottoming on carb
What I did was:
Verified no bonnet contact with the ol' grease trick. The
engine mounts were replaced last year and look good.
Got the best damn stainless steel bolt that $1.45 would buy
at Ye Olde Hardware Store.
Bought a shorter bolt. The previous bolts were purposely extra
long so that when they sheared, I could grip them from the back
and remove them without an extractor (which I don't have).
I noticed that they tended to shear at the point where the
threads ended. I figured a shorter bolt would move that
point further in. Why this would be relevant is beyond me,
but I was desperate.
Put a rubber washer on the bolt to minimize vibration transfer.
Carefully avoided my "if tight is good, tighter is better"
tendencies.
Again thanks to all. Sorry if I missed anyone.
-Greg
78 Spit - daily driver
72 Spit - NOT a parts car...
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