Engine studs - reuse or replace - non-cylinder head

[spudman5]

I'm getting ready to re-assemble my engine. One of the many item I have a question about are the mounting studs for the manifolds, themostat housing, rocker arm, rocker cover, and fuel pump. When they were removed, they received a little damage to the threads.
I can use a thread chaser or a die to clean them up and they could be reused. I assume this would be okay, since they don't under go the high stress or torque like the cylinder head studs. However, I would like some input from the experts out there.

If there is a concern about reusing them does anyone know where to find replacements for all of these studs? SS doesn't carry them and I haven't had that much success with internet searching (at least with hardened studs). Do I need to have hardened studs like the cylinder head studs or could I use a Grade 8 stud (much easier to find).

Thanks,
Mike Tanner

 

[puff4]

My opinion is to replace as many as you can, but certainly the manifold studs, since they get so much heat stress and that failure there is really a problem.

Sears Hardware has an amazing variety of studs. None of the studs other than the head studs are hardened on the Sunbeam motors, so pretty much any will do.

 

[alpine_64]

Take your time with the manifold studs.. when i was putting the exhaust headers back on in March the centre one stripped itself.. the alloy in the head can get eaten up badly with to much force

 

[Eleven]

carrollsmith.com
Nuts, bolts, fasteners and plumbing.

Must read.

 

[LarryN]

Grade 8 is probably overkill for these applications, Grade 2 is probably adequate but I would recommend Grade 5 to avoid problems with imported junk fasteners. Grade 5 is no guarantee that the fasteners won't be counterfeit, but the money is in the high-volume stuff (Grade 2) and the really expensive stuff (Grade 8).

Sounds like the studs came out without any signs of galvanic corrosion, so that's a good sign. The cylinder head is thick enough that the differential edthermal expansion between the studs and the head needs to be taken into consideration in the design - the torque has to be sufficient to put enough stretch in the stud to maintain the ability to withstand the combustion pressure even at the minimum design temperature when the head contraction outruns the stud but not so high that the expansion of the head at maximum temperature overloads either the head or the stud. The manifold and thermostat studs are short enough that the small differences in expansion don't produce any significant stress.