Valve seat cutters

[Humph7ey]

I need to know what cutters are used. The seats I have cut are 45 degrees but I want to order a cutter that opens up the throat as it is now too small. I have been offered a 30 or a 70 degree but dont know which to order. These are advertised on ebay from India with a diameter. Is this the larger or smaller?

[Humph7ey]

It is for a 1929 Austin and it is not the first time I have done valve seats as I even made new inserts from cast iron bar. Previously I made a spotfacing cutter to bore for the seats. I have a 45 degree cutter but need to open the throat of the new inserts to match the valve better. Is the cutter usually a 70 degree one for opening the throat?

[Humph7ey]

Thanks that is a great help.

[Humph7ey]

I spent most of my working life as a machinist and toolmaker but while I can still cut a thread on a lathe it is sometimes difficult to understand angles. Something to do with age.

[Humph7ey]

Thank you for all your helpful messages. I have since repaired a few old side valve engines using ordinary cast iron which was in use long before leaded fuel. I think you guys say L head.