14-09-2022, 04:16 PM
Hi
That's a bit of a mixed bag you have there.
Exhaust valves run hotter, so are sometimes made of superior material though I have no idea if this applies to A7s.
The slots are to aid turning with a big screwdriver when grinding in, and the centre dimple is (I believe) to locate the spring compressor jaw. Aftermarket valves seem to have ditched these features and have plain heads, so you need a rubber sucker for grinding.
That's a bit of a mixed bag you have there.
Exhaust valves run hotter, so are sometimes made of superior material though I have no idea if this applies to A7s.
The slots are to aid turning with a big screwdriver when grinding in, and the centre dimple is (I believe) to locate the spring compressor jaw. Aftermarket valves seem to have ditched these features and have plain heads, so you need a rubber sucker for grinding.