Cams don't have anything to do with compression ratios.

 

Think “duration...”

 

Cams do have an effect on static compression go to big boys heads plug in the bore stroke and cam you will see the numbers change when you change cam profile

 

Cams may have an effect on the power output, but they don't change the compression ratio. Compression ration just means one size of container squishing down to a different size container. Now, the right cam combination make take advantage of that better, but it doesn't change it.

 

It has an S&S carb, the module is Dynatech, not too sure about the coil or starter. I would assume Ultima......

Any suggestions?

 

Not the �ratio� per se, but the cam will affect the cranking compression number you see during a compression check.

 

I don`t really want to start a huge thread on this but I don't really see how the cam effects the ratio at all.....the compression is a direct result of F=P X A.....this is related only to the volume and size of the chamber and piston area. As volume increases pressure decreases, same reason you may have a slightly lower reading on a hot engine, (assuming we leave temperature remaining constant)

 

The cam doesn't affect the RATIO, which is a mathematical formula and is the volume of the combustion chamber at bottom dead center divided by the volume of the combustion chamber at top dead center, BUT, compression doesn't start to build in a cylinder until the intake valve closes. This is controlled by the cam. A cam with a longer duration (later closing) of the intake valve will mean the cylinder has less distance to compress the mixture, yielding a lower pressure reading than a cam with an earlier closing of the intake valve.

Remember, the compression check doesn't measure the compression RATIO, but the actual compression in the cylinder (PSI).

 

I went to compufire starter and I put a thunder jet on the super G and a atomizer or bulls eye made that motor run smooth

 

You are correct. I misspoke. I intended to say what affects the actual compression since the OP was concerned about his 175 test readings. Those values can change depending on when the intake valve closes on the compression stroke. Thus the mention of the cam in my response.