01-11-2020, 11:53 AM
From my experience, If the valve seat cutters aren't tungsten carbide, they will dull very quickly cutting seats on an early A7 block, ordinary carbon or HSS cutters won't touch modern hard valve seats.
If starting from scratch on an A7 block after opening the valve throat for big valves as in the photo below, I cut the seat, and then finish it by grinding with the B & D vibro centric tool, as Ruairidh indicates, dressing the stone regularly is key to getting a decent finish and accurate 45 degree or whatever angle.
![[Image: 29572170433_5fd909c7c5_z.jpg]](https://live.staticflickr.com/5311/29572170433_5fd909c7c5_z.jpg)
I have the B & D valve grinding machine too, once the stone in this has been dressed with a diamond, the finish on the seat is better than an 'out of the box' new valve. The B & D user manual for the two machines says that the valves don't need any lapping after this treatment. But I do give them a minute or two with some fine paste to achieve a 'full blue' print across the valve seat.
![[Image: 45068524754_7b760da2e2_z.jpg]](https://live.staticflickr.com/4868/45068524754_7b760da2e2_z.jpg)
this pic has some of the stones used with the vibro-centric tool, they are the same as used in a couple of other makes of valve seat grinders, they have a rather odd 9/16" fine thread. Maybe the OPs Sykes tool will use the same size.
![[Image: 45068530964_e5ce29f92f_z.jpg]](https://live.staticflickr.com/4854/45068530964_e5ce29f92f_z.jpg)
If starting from scratch on an A7 block after opening the valve throat for big valves as in the photo below, I cut the seat, and then finish it by grinding with the B & D vibro centric tool, as Ruairidh indicates, dressing the stone regularly is key to getting a decent finish and accurate 45 degree or whatever angle.
I have the B & D valve grinding machine too, once the stone in this has been dressed with a diamond, the finish on the seat is better than an 'out of the box' new valve. The B & D user manual for the two machines says that the valves don't need any lapping after this treatment. But I do give them a minute or two with some fine paste to achieve a 'full blue' print across the valve seat.
this pic has some of the stones used with the vibro-centric tool, they are the same as used in a couple of other makes of valve seat grinders, they have a rather odd 9/16" fine thread. Maybe the OPs Sykes tool will use the same size.