Morris Minor Owners Club

How do I tell if my head really has been converted to unleaded?

Clean the metal around one of the exhaust valves, you should see a distinct 'ring' about 1/8 inch bigger in diameter than the valve, then get a scriber and try to lightly scratch inside then outside this ring; inside should not mark as easily if the seat (insert) is hardened. If you're not convinced remove one of the exhaust valves and look for equality of the seat depth around the whole diameter, in other words clues that would indicate a seat (insert) being pressed in, as opposed to being cut into the parent metal. Sometimes this is done to reclaim a dodgy seat, but pretty rarely. If all the exhaust seats are like this you can be pretty sure you have an unleaded head.

Clean the metal around one of the exhaust valves, you should see a distinct 'ring' about 1/8 inch bigger in diameter than the valve, then get a scriber and try to lightly scratch inside then outside this ring; inside should not mark as easily if the seat (insert) is hardened. If you're not convinced remove one of the exhaust valves

How do you do this without removing a valve.
I have also been told that the exhaust valves are non magnetic as they are made from stainless steel and if you use a small magnet one of the type that looks like the end of a car aeriel it should not stick to the middle of the valve (have not tried it myself)

thanks les, in the do i fit it and see or get it re-done dilema, the valve seats are definatly a different material from the rest of the head

iain

you should see a distinct 'ring' about 1/8 inch bigger in diameter than the valve

Kevin, as this 'ring' as I describe it (actually the outside diameter of the insert if fitted) is a larger diameter than the valve it can be seen with the valve in place,

I have just looked at a 1275cc unleaded head I have just got and it is impossible to see without removing the exhaust valve as there is not enough room/clearance, maybe the 1098cc has more room ? I dont have a spare to hand to confirm.

I have also been told that the exhaust valves are non magnetic as they are made from stainless steel and if you use a small magnet one of the type that looks like the end of a car aeriel it should not stick to the middle of the valve (have not tried it myself)

Looks like I was led up the garden path with this remark as I have now been told that this is not always the case, so please ignore it.