Bolt Head Markings

[Dennis Vogel]

TLDR; Would original 356 bolts have markings on the head like "10.9", "8.8", or "8 8"?

I bought a box full of miscellaneous nuts and bolts, that was reported to be from 356, 912, 911, and 914. I culled through the stash and to my delight, found several Verbus, Kamax, etc. I hoped to use for anything missing or incorrect for our car. From disassembly of our engine, I recall that most of the bolts had "8G" on them. I don't recall any that were just numbers.

BuldNutsBolts.jpg (100.28 KiB) Viewed 1150 times

[Alan Hall]

The head marking scheme changed from a number and letter scheme to a number and number scheme at some point and I believe it was later than 356 production. The head marking refers to the strength of the bolt material and perhaps hardness. The typical 356 bolt would have been marked 8G as you remember which is equivalent to a marking of 8.8 in the newer bolts. High strength bolts were marked 10K which is equivalent to a marking of 10.9 in the newer bolts.

[Dennis Vogel]

The head marking scheme changed from a number and letter scheme to a number and number scheme at some point and I believe it was later than 356 production. The head marking refers to the strength of the bolt material and perhaps hardness. The typical 356 bolt would have been marked 8G as you remember which is equivalent to a marking of 8.8 in the newer bolts. High strength bolts were marked 10K which is equivalent to a marking of 10.9 in the newer bolts.

Thanks Alan. OK. So it sounds like I bought a bunch of 912 parts. Argh. Live and learn.