Valve Clearance

Bob Bidonde

Bob Bidonde

Well-known member
In Ford Service Bulletins, there is controversy regarding valve clearances at room temperature. Here are the clearances from the service bulletins:
Model A & B Intakes 0.010" to 0.013";
Model A Exhausts 0.010" to 0.013" or 0.015" to 0.017";
Model B Exhausts 0.020" to 0.022".

To complicate the issue further, we have modern stainless steel valves to cope with. I have not found any specific clearances for modern stainless valves which have a different coefficient of expansion than original valves.

Just in case someone asks, my motors are a Model A with a 5.5:1 compression head, and two Model B engines with 6:1 compression cylinder heads.

I want to know what the professional engine builders set the valves at.
 
For the Burtz cam. 0.012 and 0.013, intake and exhaust. Modern valves.

The clearance depends on the cam grind, mostly the ramp that closes up the gap before the valve starts to move. Of course the temperature rise and coefficient of expansion of the valves too. The ramp was introduced to modern cams to make them quieter.

If you want to know if your cam has a ramp, consult the person that did the grinding of the cam. You may be able to measure it by setting the clearance to zero then measuring the valve lift with a dial indicator at one degree or smaller crankshaft increments. When you get done plot the data and any ramp will be obvious.
 
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In my case I have no idea what cam grind my engine has. But I can see the modern stainless steel valves, checked them, and was concerned they were too tight at 0.011" for intake valves and 0.012" for exhaust valves. So I set the valve clearance to 0.013" for intake valves and 0.015" for exhaust valves. Now I have some light ticking at cold start that goes away when warmed up. The next time I'll probably go to 0.014" on the exhaust valves.
 
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