Not really enough metal there (thread length) to support helicoils so I made some stepped (`bull headed') studs. Also, 1/4 UNF thread should never have been used in alloy, it is a shallow thread and strips too easy. UNC is much better for this as it's deeper.
I bought 5/16" UNC x 3/4" Grade 5 setscrews, and turned most of the length down to 1/4", and threaded it 1/4 UNF.
Then I drilled & tapped the hinges 5/16" UNC.
Be careful doing this, remember the thread axis is at an angle to the hinge face.
I screwed the studs in with Loctite 262 super studlock.
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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
