[Joe K]

New studs are more consistent in material and formation. Plus they don't have any issue yet with corrosion - which can be a fail point. Dimensionally they are identical with old.

For the common run of the mill Model A with an original head I would re-use studs. In my most recent learning curve using a dedicated "stud puller," before the puller I ruined 2 out of 4 studs being removed. The ruination had to do with the threads trying to use the "two nut" method. After the puller - none - and all these will be re-used. I have a box full of studs from the last motor I went through and saved a majority of studs so I guess I have a complete set of used.

As to stretch - new or old stretch about the same. Modulus for steel is modulus for steel, at least until you get to things like lathe boring bars made specifically for rigidity. As to grade numbers, I would put old studs as "augmented grade 5." Grade 8 new would be stronger - but its a strength you will never use. You will pull out of the block before these break.

And there is some danger in that.

Were I to plan to go above the 55 ft-lbs of normal application I would probably use new Grade 8. As it was on the last motor I did go new grade whatever (not 8) from the supplier. But I have a standard head.

And someone said something about not having to re-torque new studs? Um, most if not all of the re-torque requirement comes from compression and thermal set of the gasket. And this won't change no matter the studs you use.

But do as you will - and by all means please report back your experience.

Joe K