Seeing that the CA18DET was a factory option in the S12, I dont see why one would be so worried about the S12 mounts. The things to consider though are: their age, the wear and tear on them, how they seem to hold when testing motors and placement of the CA18DET and how much vibration is felt around the car. S13 mounts are probably better due to age and the fact that the mounts themselves are different and in some ways use different materials.

your failure was due to difference in bolt length and thread depth in the block I seem to remember??. I think it would have been fine if the difference had been identified before.

Can't remember I'd have to look back at threads. I know it happened to Adam too. I found the pic of the what (both bolts) had remained in the block. They don't look too long to have bottomed out though.

http://img.photobucket.com/albums/v210/30psi/Stud.jpg

EDIT - Had a thought - I think one of the bolt holes in the DET block isn't used for the S13 brackets, but is for the S12 brackets. Maybe the thread isn't cut as deep as on the S12 blocks?

Oh well its in now and unless anything happens (fingers crossed) its staying put

i just used the s12 mounts on mine. Never had any issues. Just make sure all the mating surfaces dont have paint between them or paint/debris in the bolt threads. All this will cause less clampt friction force between the mating surfaces and the bolts will shear