Stripped M013 rocker bolts

[samiam4]

Guys,

I've got a 86' 300E. Can I expect to R&R valve seals without helicoiling the rocker arm bolts?? Does someone know how deep the blind holes are so I can order full-depth helicoils. I've got a standard tap and was going to buy the bottoming tap-to get full depth.
The coils are available in 1-4 diameters(8mm-24mm) from my local machinist supply company. How many should I expect to need? a few or does one ussually have to helicoil all the rocker holes.

This engine has never been touched and never overheated to the best of my knowledge.


Thanks,

Michael