I have these NOS valves

[Loffy770]

Whats the opinion on these exhaust valves?

For my engine rebuild I hav gathered pretty much all new parts.

will do rebore, decking and full grind. Will shave and aim for 8:1.

my intake valves are new made with flat discs and I like to ask if there is any negative opinions to use these slotted exhaust valves? 

[kencombs]

I think that the slot was there to accept a tab, (drive pin) on a particular valve lapping tool.  Fine to use.

[Plymouthy Adams]

if  you have a seat or detonation problem it will show up long before you have to worry about that slot....as stated...posi lock for lapping valves has always been my use of these...hard to find valves with this feature...

[Loffy770]

Thanks guys