The good news is I have"repaired" several of those with heli-coils when the customer couldnt afford a proper repair. I ve never had issues with helicoils although its not an ideal solution.
I recomend doing all of them at the same time.
What's less than ideal about a helicoil for this repair? I've not seen any issues with helicoils, 1 1/2 diameters or longer, except on stuff that's regularly disassembled. Steel inserts are definitely better for stuff that gets tore down frequently.
Since this appears to be a known issue it makes sense to do all of 'em while you're in there. The helicoil kit will probably come with enough inserts to do the whole head so it won't cost anything but time.

Oh got it all done already, good job.You got it done quick.
Was the valve cover hard to get at?
Had to take off the UIM?
Was it easy to get to the bolt hole to drill/tap it for the H-coil?
Oh got it all done already, good job.You got it done quick.
Was the valve cover hard to get at?
Had to take off the UIM?
Was it easy to get to the bolt hole to drill/tap it for the H-coil?
You only need to remove the water pipe and disconnect the o2 sensor and possibly the torque mounts depending on year to get the front valve cover off those engines. The front heads are easy to get at, but the rear gets a little more time consuming.
Good job OP, I wish I would have chimed in a little earlier and saved ya some time. Dont be surprised if another pops out in a couple of months. At least you'll be prepared this time.
What motor is this? Is this the 3.4L.
I have a 3.4 L in my Alero, hope this is not a problem with my motor. Intake gaskets were already replaced.
