ARP finally fixes main stud to oil pump problems.

moper said

I don't mix and match fasteners either. Studs load the cap and block differently from a bolt. It may never be a problem - but doing it will cause stress risers in the block and cap and can distort the cap's main bearing surface. It's similar to torquing one bolt on a head to 200lbs, and leaving the others at 85. SoI figured I'd take the 10 minutes it takes to cut down the stud and use a 12pt nut. BTW - I'm fairly certain .050" isn't enough to fix it...

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I put main studs in a 360 block. At the time I didn't know any better. All machine work had been done to the block before I decided to do this. I was talking to my machinist one day and happened to mention I had decided to install main studs. He informed me that studs can sometimes cause a change in the mains once torqued down. He told me to bring it back and he would check it to be safe. All was well in my case but it undoubtedly happens and could very well happen, especially with a stud and a bolt on the same cap.