Q: If on a radial engine (specifically a Warner) one finds one stud broken at the flange level, would you recommend replacing all the affected cylinder studs? I assume cylinder movement caused the break.
Gennaro Avolio
A: I believe in this particular situation I would only replace the broken stud. However, I would very closely inspect all of the other studs and inspect the parting surfaces of the cylinder base and where it attaches to the crankcase for any sign of fretting or indications of metal movement.
The only reason I am suggesting you replace the broken stud is simply because of the low compression of this engine. It would concern me more if the engine compression were higher, which could have caused a more serious condition on all of the components.
Note the 3/8″ studs remove the inspection requirements of the AD not the requirement to replace all studs on an effected cyl. if one is found broken.
On the Warner engines AD 54-4-2 requires that all studs be replaced on the affected cylinder when one is found broken. If found loose it is recommended that they be replaced as the studs my have stretched. This is for 5/15 studs with a base gasket or “O” ring seal. The torque is to be checked every 100hrs as well. Switching to 3/8 studs and “O” ring base seal will eliminate the repetitive inspection of torque,(the torque spec. changes as well). If a letter “A” is stamped after the serial number this mod. has been accomplished, however it would be good to check what studs are installed as many parts could have been changed since this AD came out and the data plate may not reflect what is really on the engine anymore.