I apologize that I did not warn you. when laying in the cam and rocker arms, you have to start all the bolts and tighten them down evenly all around. I would think that helicoiling would work fine. After the helicoil is in place lay everything in and tighten each just a little at a time all around. Keep moving around 'till you have pulled everything down.
I was warned about this before laying the cam and rockers on mine, and I forgot to pass this warning along.