[Bob Bidonde]

Stainless steel replacement valves for Model A & B engines are the same material for intake and exhaust valves.


The most common stainless steels for automotive exhaust valves are 21-2N and 21-4N. These are austenitic steels:

21-2N = 21% Chromium & 2% Nickle and so forth.


Valve clearance is a function of linear thermal expansion. Stainless steel does not conduct heat as well as carbon steel, so I would guess that the valve clearances for stainless valves would be equal to or perhaps less than Ford's original valves.



I run my engines with stainless valves at the Model B engine specs of 0.013" intakes and 0.015" exhausts. When the engine is cold, there is no valve clatter with these clearances.


Valve clatter (Noise) is a sign that the impact energy acting on the valve train is higher than it should be.