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It depends on what the threads are like Bill. I take it you have all the tappets backed off fully and the rocker arms held up out of the way with rubber bands and if possible, someone pushing the cover down flat when you're trying to do the bolts up to reduce the pressure?. It's very rare to pull helicoils out unless there is an awful lot of pressure being exerted on them. If the helicoils had have been loose, why didn't they come out when you stripped the top end down 🤔🤔🤔It's very, very easy to bend valves and crack the valve guides without taking the pressure off by doing the above.
If they have unscrewed you can replace them, if they have pulled out its a problem.Are they short coils in deep holes? If so an answer is possible but complicated, i dont think there is metal for timeserts(they need a 10mm outer thread)
While torquing up the 4 bolts on cam cover, 3 wouldn't tighten.
Get yourself a V-coil kit and re-tap and put a new coil in >>> Link >> https://www.ebay.co.uk/itm/354074603431?hash=item52707dafa7:g:jqIAAOSw3qpimPFJ