Flywheel minimum thickness? Options

[Cazz]

My flywheel is grooved and needs to be machined.
-Does anyone know the minimum thickness of the flywheel surface where the clutch disc mates?
-the thickness I get using my cheap calipers is 4mm thickness on the face.
-what is the minimum thickness after a machine shop cuts the face?

[Mark Henry]

Just speculation, but I think the reason there was no spec with the original /4 is because it had the 4 spring clutch disc, likely the dealer would say it's a one use only and replace the flywheel. With the original 4 spring disc you were lucky if you could cut it once, even grinding down the bolts, as it would hit the big ass disc springs.
If I'm correct on this it would explain why we can't find a spec anywhere for the /4 flywheel.

I know the fitment issue is fact as I had an NOS 4 spring back in the day, IIRC I had to use an uncut fly to use the thing. Also my 914 was a low mile dealer maintained car and had the bill for a clutch job at 56K, it said the flywheel was replaced. Late 80's bill, tune-up, oil, RMS and clutch was something like $1300.

The /6 six (small) spring disc has way more clearance and with grinding the bolts has 3-4 surface grinds before it becomes an issue.