Did the Timing belt today on my99 V70 286K miles.

Al went great.

One issue was, while installing the crank pulley, one of the small 4 bolts (10mm)
broke off inside; over tightened it. Doesn't seem to be a huge problem, That pulley is not going anywhere. I wonder about the crank balance now. Should I bring the car to a machine shop and have them remove the busted part and put a new bolt in. Or should i remove the opposite bolt to equal the balance? Perhaps just epoxy the busted part back into the hole for balance.

Thanks.

Agree, replace the bolt, can you remove the pulley and remove the remaining bit of bolt with a pliers, it shouldn't be tight. You want all 4 in there, this isn't the piece you want to wobble.

The balance will not be affected, too close to the center point. But, I would certainly want to replace that bolt. With the passage of time, the pulley may no longer lie flat and start to wobble? Like driving with a missing lug bolt.
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My back feels better when I sit in a Volvo seat