Helicoil or Timesert (thread insert) a Stripped headbolt block hole?

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    So one and possibly 2 of the head bolt holes in the block that also hold down the rocker arm assembly are stripped out. Engine is fully assembled in the car. Head, valve train, and intake are removed. The hole that is completely stripped previously had a crack and the crack on the valley side that was welded up when the engine was rebuilt about 3000 miles ago. There was no thread repair done in that hole as far as I can tell.

    Both the Helicoil and the Timesert drill out the hole for the 7/16″ bolt to 29/64″ and tap it with a special STI tap with a outside thread diameter of 0.534″. Since these holes are on the inside edge of the block deck at the lifter valley, the hole wall is getting kinda thin and I am concerned about the pressure the thead insert type will exert with it’s expanding “binding” threads.

    Wondering if anyone has had experience repairing these holes specifically or other head bolt holes in general?
    Have you used the Helicoil or a thread insert like Timesert?
    How did it work out when you torqued down the head?

    See pics attached



    ckd notify.


    I used a Helicoil in one of the head bolt holes on the first 215 I built decades ago. Timeserts didn’t exist then. No issues at all.


    Thanks Joe. The machine shop thinks that’s the way to go too. Think I’ll go that way as well.
    My rocker assembly is up to get a new shaft and rocker and checked out.

    The rebuilder up in Northern Calif, I’ve heard he’s the guy everyone goes to including D&D, is going to come out with a stronger shaft option. Not available yet but will be after the 1st sometime if anyone is interested. He said there is an issue with it breaking at the end, on pumped up engines I guess. I do see that those stronger shafts are available for the other Buick engines with the same type of valve train.


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