I worked in the auto machine shop biz for 25 years. That biz has change hands 6 times in the 18 years since I retired. I have invested in the correct tooling for Serdi,  seat cutters and seats which I drop off with the heads. It saves a lot of time and most shops don't deal with the size we need. I'm a little concerned about your shop. I'd think there are still progressive size charts for seats. If we can't get the size seat we need we machine from a larger blank. Yes, they are tough and hard but can be machined. I have about 8 to 10 cyl heads needing rebuilt now. Have had one ready for awhile just sold it with a job. Would love to have these all done and ready. It is possible to have exhaust seat issues. I had a customer drive across country and back around 6000 miles and one exhaust started closing up. He returned the head for a redo with hard seats. I believe it is back in service with no issues now. Steve (CTR)

Our host offers them.

//www.minimania.com/part/ST585/Classic-Austin-Mini-Valve-Seat-131-Intake

//www.minimania.com/part/TAM2069/Classic-Austin-Mini-Seat-Exhaust-Valve-115-1275-Lead-Free

//www.minimania.com/part/TAM2068/Classic-Austin-Mini-Exhaust-Valve-Seat-10-Lead-Free

I had hardened exhaust seats installed in my OEM Cooper head and seats cut for larger Paul Ivey race valves when I was in Australia this year.  Russell Engineering had the seats I needed and Graham Russell did the work.  I should think any machine shop that has worked with A Series heads should solve your issue PDQ.

Graham did a little clean up under the seats after they were installed and all cut for larger valves

Fellow Minioids,  My machinist is having a difficult time finding hardened valve seats for my 12G940 head.  I want to have the hardened seats pressed in but he says that the seats he has access to are too big and he is afraid they will not work.  I am going to port the head soon and then have him install the seats, should I even find them.  Any sources out there?  Also, is it really even necessary?   I know that there are claims of valve seat recession, but how much and how many miles of use????  I only plan on a couple thousand miles per year.

Dogscarf
1967 Morris Cooper S Aussie.
1968 Morris Cooper S.