Technical replace all my oil pump cover bolts?

so I was tightening up my oil pump bolts and one of the heads cracked off luckily i was able to easily remove the rest of the bolt but my question now is do I replace all 4 bolts or just the broken one (which I have already done in the photo) , I only asking because I just want to do the correct thing since once the pans on its done. I'm using zinc plated bolts is that ok as well? Thanks, Joshua

 

Those are grade 2 … replace with grade 5 although 2 is plenty. I would use star washers. 8 psi torque for grade 2 and 13 psi using grade 5; they are 5/16” co**** ….ACE hardware.

 

how do I tell which grade it is?

 

thank you! now my last question would be should I just replace all 4 of the bolts?

 

Yes, replace all 4.

 

And make sure none of them bottom out in a blind hole before they get tight.

 

A tiny drop of Blue Loc***e would not hurt either.

 

thank you all for the suggestions, I went to ace and bought 4 new grade 5 screws, and then used blue loc***e on all of them.

 

On my first car I did similar, but only replaced the bolt that I broke, overtightening.
No problems.

 

Ya did it properly. If I didn’t have a bolt that would work, I’d have done all 4 as well.