Need combustion chamber volume's

walt jones

walt jones

Senior Member
Can anyone tell me the volume in CCs of the combustion chamber In : 1. a stock Model A head, 2. a Snyder's 5.5:1 head, 3. a Snyder's 6:1 head ?
I have purchased an HC head and am trying to determine which head that I have.

Thanks
 
Maybe call Snyders? They must have a way to tell their two different products apart?

Joe K
 
A lot depends on how much your pistons hang out above the block, as well as the bore (oversize) of your block, but a combustion chamber volume of about 150cc's should get you close to 6:1.
 
I would think that the answer to your question can be easily calculated.

With the stock model A having a bore and stroke of 3.875" X 4.125", you can calculate the volume that the piston displaces on its travel to be 48.65 cubic inches.

Now, with the stock head I think the compression ratio is 4.22 to 1.

Now, the 1 is the volume left in the head when the piston is at TDC and the 4.22-1 = 3.22 is the volume that the piston displaces.

Hence the volume of the chamber in the stock head equals 48.65 cu. in / 3.22 = 15.11 cu. in or 247.6cc

For the 5.5 to 1 head, the volume of the head chamber should be 10.81 cu. in or 177.2 cc

For the 6 to 1 head, the volume of the head chamber should be 9.729 cu. in or 159.4 cc
 
We may not actually be able to tell you what kind of head that you have as there have been easily a dozen or more manufacturers of high compression heads over the years. That said, there is a Ford reference to the stock head having something like 242 CC. I have a new Snyder 5.5/1 head that measures 168 CC and another old head of unknown provenance measuring 147cc, which I take to be around 6.2/1. One variable is the choice of head gasket, as some will compress more than others.
 
I thought about posting the mathematical answer that Eystein posted, but took the lazy way out after going through the math. The only thing I would like to add to that post is that the head gasket volume (more than you might think), Valve head volume (enough to make a little difference), and the aforementioned piston/deck height volume must be considered. When they are taken into account, the 150 cc chamber comes very close to yielding a 6:1 ratio on the average rebuilt A engine.
 
You don't need CC to distinguish the differences between those heads as all three have different shaped combustion chambers. Post a picture of what you have and we can likely tell you.
 
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