valve clearence
 

reminder on what the Model a valve clearance is . thanks, steve

Re: valve clearence
 

Many answers depending where you find it. I set mine intake at .010 and exhaust at .012, no closer.

Re: valve clearence
 

There were 4 changes in 1928 in the service bulletins.

I set mine at .010 intake and .013 exhaust.

RICHARD
ANAHEIM CA

Re: valve clearence
 

Depends on what the valves are made of. I recently had a camshaft reground and the people who did it said 0.025" on the exhaust with stainless valves. I settled on 0.022" and all has been well. Noisy while the motor is cold but quieten right down as it warms up.
He told of a guy who had put stainless valves in his Model T and set the clearances as per spec. When things weren't working out, an inspection of the camshaft showed that the followers were rubbing the heel of the cam - hard. They opened the gap to 0.025" and all has been well there too.

Re: valve clearence
 

Always follow the rebuilders recommendation, but he was asking about Model A specs. Modified engines need to be looked at carefully.

Re: valve clearence
 

Wise advice but how many Model As are running original valves? If they have been replaced with modern steels, things change.

Re: valve clearence
 

what makes the valves noisy to loose or to tight? these are stock valves, old school

Re: valve clearence
 

Too loose makes noisey

Re: valve clearence
 

Well, if everything is stock then the valves are not adjustable. At least they are not easily adjusted, to adjust the originals the stem requires grinding or seats need cutting depending on the clearance.

Re: valve clearence
 

I use stainless steel valves with the original mushroom style stem . I use adjustable lifters and adjust for sixteen thousands clearance . This same clearance of sixteen thousands was recommended for both intake and exhaust valves by the grinder of my super street Winfield 3/4 race regrind cams . Less clearance gives a small fraction more lift . Extra clearance gives more time on the valve seat for more cooling of the valves and less chance of burning a valve . In the past , Snyders recommended sixteen thousands clearance .

Re: valve clearence
 

Duration also changes slightly, less clearance gives more duration. Too little clearance can cause valves to burn. I recommend .012" on intakes, .014" exhausts on my B and C re-grinds, which were taken off stock original cams.

Re: valve clearence
 

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.